x86/dumpstack: Cleanups and user opcode bytes Code: section, v3
Subsystems (4)
Borislav Petkov
maintainercover x86/dumpstack: Cleanups and user opcode bytes Code: section, v3
From: Borislav Petkov <[email protected]>
Hi,
here's v3 now that the merge window is done, with hopefully all review feedback (thanks Josh et al!) incorporated.
Thx.
Borislav Petkov (9):
x86/dumpstack: Remove code_bytes
x86/dumpstack: Unexport oops_begin()
x86/dumpstack: Carve out Code: dumping into a function x86/dumpstack: Improve opcodes dumping in the Code: section x86/dumpstack: Add loglevel argument to show_opcodes() x86/fault: Dump user opcode bytes on fatal faults x86/dumpstack: Add a show_ip() function
x86/dumpstack: Save first regs set for the executive summary x86/dumpstack: Explain the reasoning for the prologue and buffer size
Documentation/admin-guide/kernel-parameters.txt | 5 - arch/x86/include/asm/stacktrace.h | 2 + arch/x86/kernel/dumpstack.c | 144 ++++++++++++------------ arch/x86/kernel/process_32.c | 8 +- arch/x86/mm/fault.c | 7 +- 5 files changed, 80 insertions(+), 86 deletions(-)
Signature · 339 lines
2.13.0 Changelog: v2: here's v2 with the dumpstack cleanups. This one gets rid of code_bytes= as it was discussed last time. As a result, the code got even leaner and simpler. I like that. :) Thx. Borislav Petkov (9): x86/dumstack: Remove code_bytes x86/dumpstack: Unexport oops_begin() x86/dumpstack: Carve out Code: dumping into a function x86/dumpstack: Improve opcodes dumping in the Code: section x86/dumpstack: Add loglevel argument to show_opcodes() x86/fault: Dump user opcode bytes on fatal faults x86/dumpstack: Add a show_ip() function x86/dumpstack: Save first regs set for the executive summary x86/dumpstack: Explain the reasoning for the prologue and buffer size Documentation/admin-guide/kernel-parameters.txt | 5 - arch/x86/include/asm/stacktrace.h | 2 + arch/x86/kernel/dumpstack.c | 138 ++++++++++++------------ arch/x86/kernel/process_32.c | 4 +- arch/x86/mm/fault.c | 7 +- 5 files changed, 78 insertions(+), 78 deletions(-) v1: Hi, here's v2 of the dumpstack cleanups. I've split them into more fine-grained pieces to show each change. The relevant parts are the saving of the executive registers of the first time we oops and dumping them in the end + opcode bytes for user faults. I've tested splats in a 80x25 screen and the registers, RIP and opcode bytes fit all in. I'm adding exemplary dumps from 32-bit and 64-bit at the end of this mail. I still have on my TODO list to experiment with console log levels and see whether we can do a best-of-both-worlds thing there. v0: Hi, so I've been thinking about doing this for a while now: be able to dump the opcode bytes around the user rIP just like we do for kernel faults. Why? See patch 5's commit message. That's why I've marked it RFC. The rest is cleanups: we're copying the opcodes byte-by-byte and that's just wasteful. Also, we're using probe_kernel_read() underneath and it does __copy_from_user_inatomic() which makes copying user opcode bytes trivial. With that, it looks like this: [ 696.837457] strsep[1733]: segfault at 40066b ip 00007fad558fccf8 sp 00007ffc5e662520 error 7 in libc-2.26.so[7fad55876000+1ad000] [ 696.837538] Code: 1b 48 89 fd 48 89 df e8 77 99 f9 ff 48 01 d8 80 38 00 75 17 48 c7 45 00 00 00 00 00 48 83 c4 08 48 89 d8 5b 5d c3 0f 1f 44 00 00 <c6> 00 00 48 83 c0 01 48 89 45 00 48 83 c4 08 48 89 d8 5b 5d c3 and the code matches, as expected: 0000000000086cc0 <__strsep_g@@GLIBC_2.2.5>: 86cc0: 55 push %rbp 86cc1: 53 push %rbx 86cc2: 48 83 ec 08 sub $0x8,%rsp 86cc6: 48 8b 1f mov (%rdi),%rbx 86cc9: 48 85 db test %rbx,%rbx 86ccc: 74 1b je 86ce9 <__strsep_g@@GLIBC_2.2.5+0x29> 86cce: 48 89 fd mov %rdi,%rbp 86cd1: 48 89 df mov %rbx,%rdi 86cd4: e8 77 99 f9 ff callq 20650 <*ABS*+0x854e0@plt> 86cd9: 48 01 d8 add %rbx,%rax 86cdc: 80 38 00 cmpb $0x0,(%rax) 86cdf: 75 17 jne 86cf8 <__strsep_g@@GLIBC_2.2.5+0x38> 86ce1: 48 c7 45 00 00 00 00 movq $0x0,0x0(%rbp) 86ce8: 00 86ce9: 48 83 c4 08 add $0x8,%rsp 86ced: 48 89 d8 mov %rbx,%rax 86cf0: 5b pop %rbx 86cf1: 5d pop %rbp 86cf2: c3 retq 86cf3: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 86cf8: c6 00 00 movb $0x0,(%rax) 86cfb: 48 83 c0 01 add $0x1,%rax 86cff: 48 89 45 00 mov %rax,0x0(%rbp) 86d03: 48 83 c4 08 add $0x8,%rsp 86d07: 48 89 d8 mov %rbx,%rax 86d0a: 5b pop %rbx 86d0b: 5d pop %rbp 86d0c: c3 retq Comments and suggestions are welcome! Thx. Example dumps v3: 64-bit: [ 34.688928] sysrq: SysRq : Trigger a crash [ 34.690799] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 34.692653] PGD 7aac2067 P4D 7aac2067 PUD 7aac3067 PMD 0 [ 34.692653] Oops: 0002 [#1] PREEMPT SMP [ 34.692653] CPU: 0 PID: 3695 Comm: bash Not tainted 4.16.0+ #14 [ 34.692653] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 34.692653] RIP: 0010:sysrq_handle_crash+0x17/0x20 [ 34.692653] Code: d1 e8 9d f1 b6 ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 e8 46 0c bd ff c7 05 74 0e 19 01 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 c3 0f 1f 44 00 00 e8 46 0a c2 ff fb e9 30 [ 34.692653] RSP: 0018:ffffc90001b57df0 EFLAGS: 00010246 [ 34.692653] RAX: 0000000000000000 RBX: 0000000000000063 RCX: 0000000000000000 [ 34.692653] RDX: 0000000000000000 RSI: ffffffff81101f2a RDI: 0000000000000063 [ 34.692653] RBP: ffffffff8226fec0 R08: 0000000000000183 R09: 00000000000a8320 [ 34.692653] R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a [ 34.692653] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 34.692653] FS: 00007ffff7fdb700(0000) GS:ffff88007ec00000(0000) knlGS:0000000000000000 [ 34.692653] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 34.692653] CR2: 0000000000000000 CR3: 0000000079462000 CR4: 00000000000406f0 [ 34.692653] Call Trace: [ 34.692653] __handle_sysrq+0x9e/0x160 [ 34.692653] write_sysrq_trigger+0x2b/0x30 [ 34.692653] proc_reg_write+0x38/0x70 [ 34.692653] __vfs_write+0x36/0x160 [ 34.692653] ? __fd_install+0x69/0x110 [ 34.692653] ? preempt_count_add+0x74/0xb0 [ 34.692653] ? _raw_spin_lock+0x13/0x30 [ 34.692653] ? set_close_on_exec+0x41/0x80 [ 34.692653] ? preempt_count_sub+0xa8/0x100 [ 34.692653] vfs_write+0xc0/0x190 [ 34.692653] ksys_write+0x64/0xe0 [ 34.692653] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 34.692653] do_syscall_64+0x70/0x130 [ 34.692653] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 34.692653] RIP: 0033:0x7ffff74b9620 [ 34.692653] Code: 73 01 c3 48 8b 0d 68 98 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d bd f1 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ce 8f 01 00 48 89 04 24 [ 34.692653] RSP: 002b:00007fffffffe6f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 34.692653] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007ffff74b9620 [ 34.692653] RDX: 0000000000000002 RSI: 0000000000705408 RDI: 0000000000000001 [ 34.692653] RBP: 0000000000705408 R08: 000000000000000a R09: 00007ffff7fdb700 [ 34.692653] R10: 00007ffff77826a0 R11: 0000000000000246 R12: 00007ffff77842a0 [ 34.692653] R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000 [ 34.692653] Modules linked in: [ 34.692653] CR2: 0000000000000000 [ 34.728373] ---[ end trace 84a5f329ce73ad83 ]--- [ 34.730511] RIP: 0010:sysrq_handle_crash+0x17/0x20 [ 34.732585] Code: d1 e8 9d f1 b6 ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 e8 46 0c bd ff c7 05 74 0e 19 01 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 c3 0f 1f 44 00 00 e8 46 0a c2 ff fb e9 30 [ 34.739863] RSP: 0018:ffffc90001b57df0 EFLAGS: 00010246 [ 34.740612] RAX: 0000000000000000 RBX: 0000000000000063 RCX: 0000000000000000 [ 34.741653] RDX: 0000000000000000 RSI: ffffffff81101f2a RDI: 0000000000000063 [ 34.742585] RBP: ffffffff8226fec0 R08: 0000000000000183 R09: 00000000000a8320 [ 34.743517] R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a [ 34.744500] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 34.745626] FS: 00007ffff7fdb700(0000) GS:ffff88007ec00000(0000) knlGS:0000000000000000 [ 34.746691] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 34.747422] CR2: 0000000000000000 CR3: 0000000079462000 CR4: 00000000000406f0 [ 34.748382] Kernel panic - not syncing: Fatal exception [ 34.749531] Kernel Offset: disabled [ 34.750005] ---[ end Kernel panic - not syncing: Fatal exception ]--- 32-bit: [ 103.959732] sysrq: SysRq : Trigger a crash [ 103.964190] BUG: unable to handle kernel NULL pointer dereference at 00000000 [ 103.968108] *pde = 00000000 [ 103.968108] Oops: 0002 [#1] PREEMPT SMP [ 103.968108] CPU: 5 PID: 2117 Comm: bash Not tainted 4.16.0+ #15 [ 103.968108] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 103.968108] EIP: sysrq_handle_crash+0x1d/0x30 [ 103.968108] Code: ff eb d6 e8 a5 f4 b9 ff 90 8d 74 26 00 0f 1f 44 00 00 55 89 e5 e8 03 f0 bf ff c7 05 34 b2 c1 c1 01 00 00 00 0f ae f8 0f 1f 00 <c6> 05 00 00 00 00 01 5d c3 8d 76 00 8d bc 27 00 00 00 00 0f 1f 44 [ 103.968108] EAX: 00000000 EBX: 0000000a ECX: 00000000 EDX: c1505ad0 [ 103.968108] ESI: 00000063 EDI: 00000000 EBP: f374fe80 ESP: f374fe80 [ 103.968108] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246 [ 103.968108] CR0: 80050033 CR2: 00000000 CR3: 33044000 CR4: 000406d0 [ 103.968108] Call Trace: [ 103.968108] __handle_sysrq+0x93/0x130 [ 103.968108] ? sysrq_filter+0x3c0/0x3c0 [ 103.968108] write_sysrq_trigger+0x27/0x40 [ 103.968108] proc_reg_write+0x4d/0x80 [ 103.968108] ? proc_reg_poll+0x70/0x70 [ 103.968108] __vfs_write+0x38/0x160 [ 103.968108] ? preempt_count_sub+0xa0/0x110 [ 103.968108] ? set_close_on_exec+0x4b/0x60 [ 103.968108] ? preempt_count_sub+0xa0/0x110 [ 103.968108] ? __fd_install+0x51/0xd0 [ 103.968108] ? __sb_start_write+0x4c/0xc0 [ 103.968108] ? preempt_count_sub+0xa0/0x110 [ 103.968108] vfs_write+0x98/0x180 [ 103.968108] ksys_write+0x51/0xb0 [ 103.968108] SyS_write+0x16/0x20 [ 103.968108] do_fast_syscall_32+0x99/0x200 [ 103.968108] entry_SYSENTER_32+0x53/0x86 [ 103.968108] EIP: 0xb7f71b35 [ 103.968108] Code: 89 e5 8b 55 08 8b 80 64 cd ff ff 85 d2 74 02 89 02 5d c3 8b 04 24 c3 8b 0c 24 c3 8b 1c 24 c3 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90 8d 76 [ 103.968108] EAX: ffffffda EBX: 00000001 ECX: 09b11a08 EDX: 00000002 [ 103.968108] ESI: 00000002 EDI: b7f3cd80 EBP: 09b11a08 ESP: bfeeb390 [ 103.968108] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000246 [ 103.968108] Modules linked in: [ 103.968108] CR2: 0000000000000000 [ 104.023961] ---[ end trace 705add298921f2dd ]--- [ 104.025249] EIP: sysrq_handle_crash+0x1d/0x30 [ 104.026323] Code: ff eb d6 e8 a5 f4 b9 ff 90 8d 74 26 00 0f 1f 44 00 00 55 89 e5 e8 03 f0 bf ff c7 05 34 b2 c1 c1 01 00 00 00 0f ae f8 0f 1f 00 <c6> 05 00 00 00 00 01 5d c3 8d 76 00 8d bc 27 00 00 00 00 0f 1f 44 [ 104.034894] EAX: 00000000 EBX: 0000000a ECX: 00000000 EDX: c1505ad0 [ 104.036643] ESI: 00000063 EDI: 00000000 EBP: f374fe80 ESP: c1c1187c [ 104.038432] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246 [ 104.040185] CR0: 80050033 CR2: 00000000 CR3: 33044000 CR4: 000406d0 [ 104.041826] Kernel panic - not syncing: Fatal exception [ 104.043607] Kernel Offset: disabled [ 104.044170] ---[ end Kernel panic - not syncing: Fatal exception ]--- v2: 64-bit: [ 53.534957] sysrq: SysRq : Trigger a crash [ 53.536939] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 53.539982] PGD 79149067 P4D 79149067 PUD 793a5067 PMD 0 [ 53.540897] Oops: 0002 [#1] PREEMPT SMP [ 53.540897] CPU: 6 PID: 3700 Comm: bash Not tainted 4.16.0-rc5+ #11 [ 53.540897] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 53.540897] RIP: 0010:sysrq_handle_crash+0x17/0x20 [ 53.540897] Code: d1 e8 6d 08 b7 ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 e8 76 1f bd ff c7 05 a4 12 19 01 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 c3 0f 1f 44 00 00 e8 c6 1b c2 ff fb e9 80 [ 53.540897] RSP: 0018:ffffc9000053bdf0 EFLAGS: 00010246 [ 53.540897] RAX: 0000000000000000 RBX: 0000000000000063 RCX: 0000000000000000 [ 53.540897] RDX: 0000000000000000 RSI: ffffffff81101e0a RDI: 0000000000000063 [ 53.540897] RBP: ffffffff822714c0 R08: 0000000000000185 R09: 00000000000829ad [ 53.540897] R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a [ 53.540897] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 53.540897] FS: 00007ffff7fdb700(0000) GS:ffff88007ed80000(0000) knlGS:0000000000000000 [ 53.540897] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 53.540897] CR2: 0000000000000000 CR3: 0000000079107000 CR4: 00000000000406e0 [ 53.540897] Call Trace: [ 53.540897] __handle_sysrq+0x9e/0x160 [ 53.540897] write_sysrq_trigger+0x2b/0x30 [ 53.540897] proc_reg_write+0x38/0x70 [ 53.540897] __vfs_write+0x36/0x160 [ 53.540897] ? __fd_install+0x69/0x110 [ 53.540897] ? preempt_count_add+0x74/0xb0 [ 53.540897] ? _raw_spin_lock+0x13/0x30 [ 53.540897] ? set_close_on_exec+0x41/0x80 [ 53.540897] ? preempt_count_sub+0xa8/0x100 [ 53.540897] vfs_write+0xc0/0x190 [ 53.540897] SyS_write+0x64/0xe0 [ 53.540897] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 53.540897] do_syscall_64+0x70/0x130 [ 53.540897] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 53.540897] RIP: 0033:0x7ffff74b9620 [ 53.540897] Code: 73 01 c3 48 8b 0d 68 98 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d bd f1 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ce 8f 01 00 48 89 04 24 [ 53.540897] RSP: 002b:00007fffffffe6f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 53.540897] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007ffff74b9620 [ 53.540897] RDX: 0000000000000002 RSI: 0000000000705408 RDI: 0000000000000001 [ 53.540897] RBP: 0000000000705408 R08: 000000000000000a R09: 00007ffff7fdb700 [ 53.540897] R10: 00007ffff77826a0 R11: 0000000000000246 R12: 00007ffff77842a0 [ 53.540897] R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000 [ 53.540897] Modules linked in: [ 53.540897] CR2: 0000000000000000 [ 53.576029] ---[ end trace 9b6fe8eba592293d ]--- [ 53.578109] RIP: 0010:sysrq_handle_crash+0x17/0x20 [ 53.580191] Code: d1 e8 6d 08 b7 ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 e8 76 1f bd ff c7 05 a4 12 19 01 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 c3 0f 1f 44 00 00 e8 c6 1b c2 ff fb e9 80 [ 53.587244] RSP: 0018:ffffc9000053bdf0 EFLAGS: 00010246 [ 53.587928] RAX: 0000000000000000 RBX: 0000000000000063 RCX: 0000000000000000 [ 53.588929] RDX: 0000000000000000 RSI: ffffffff81101e0a RDI: 0000000000000063 [ 53.589956] RBP: ffffffff822714c0 R08: 0000000000000185 R09: 00000000000829ad [ 53.590886] R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a [ 53.591812] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 53.592781] Kernel panic - not syncing: Fatal exception [ 53.594100] Kernel Offset: disabled [ 53.594571] ---[ end Kernel panic - not syncing: Fatal exception ]--- [ 22.737752] strsep[3728]: segfault at 40066b ip 00007ffff7abe22b sp 00007fffffffea60 error 7 in libc-2.19.so[7ffff7a33000+19f000] [ 22.742487] Code: 48 89 fd 53 48 83 ec 08 48 8b 1f 48 85 db 74 67 0f b6 06 84 c0 74 33 80 7e 01 00 74 22 48 89 df e8 5a 8a ff ff 48 85 c0 74 20 <c6> 00 00 48 83 c0 01 48 89 45 00 48 89 d8 48 83 c4 08 5b 5d c3 0f 32-bit ------ [ 151.053373] sysrq: SysRq : Trigger a crash [ 151.056586] BUG: unable to handle kernel NULL pointer dereference at 00000000 [ 151.060237] *pde = 00000000 [ 151.060484] Oops: 0002 [#1] PREEMPT SMP [ 151.060484] CPU: 1 PID: 2070 Comm: bash Not tainted 4.16.0-rc5+ #12 [ 151.060484] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 151.060484] EIP: sysrq_handle_crash+0x1d/0x30 [ 151.060484] Code: ff eb d6 e8 75 0f ba ff 90 8d 74 26 00 0f 1f 44 00 00 55 89 e5 e8 03 07 c0 ff c7 05 34 72 c1 c1 01 00 00 00 0f ae f8 0f 1f 00 <c6> 05 00 00 00 00 01 5d c3 8d 76 00 8d bc 27 00 00 00 00 0f 1f 44 [ 151.060484] EAX: 00000000 EBX: 0000000a ECX: 00000000 EDX: c1503f70 [ 151.060484] ESI: 00000063 EDI: 00000000 EBP: f36d7e8c ESP: f36d7e8c [ 151.060484] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 [ 151.060484] CR0: 80050033 CR2: 00000000 CR3: 33d64000 CR4: 000406d0 [ 151.060484] Call Trace: [ 151.060484] __handle_sysrq+0x93/0x130 [ 151.060484] ? sysrq_filter+0x3c0/0x3c0 [ 151.060484] write_sysrq_trigger+0x27/0x40 [ 151.060484] proc_reg_write+0x4d/0x80 [ 151.060484] ? proc_reg_poll+0x70/0x70 [ 151.060484] __vfs_write+0x38/0x160 [ 151.060484] ? preempt_count_sub+0xa0/0x110 [ 151.060484] ? __fd_install+0x51/0xd0 [ 151.060484] ? __sb_start_write+0x4c/0xc0 [ 151.060484] ? preempt_count_sub+0xa0/0x110 [ 151.060484] vfs_write+0x98/0x180 [ 151.060484] SyS_write+0x4f/0xb0 [ 151.060484] do_fast_syscall_32+0x99/0x200 [ 151.060484] entry_SYSENTER_32+0x53/0x86 [ 151.060484] EIP: 0xb7f25b35 [ 151.060484] Code: 89 e5 8b 55 08 8b 80 64 cd ff ff 85 d2 74 02 89 02 5d c3 8b 04 24 c3 8b 0c 24 c3 8b 1c 24 c3 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90 8d 76 [ 151.060484] EAX: ffffffda EBX: 00000001 ECX: 08b14a08 EDX: 00000002 [ 151.060484] ESI: 00000002 EDI: b7ef0d80 EBP: 08b14a08 ESP: bfc53830 [ 151.060484] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b [ 151.060484] Modules linked in: [ 151.060484] CR2: 0000000000000000 [ 151.128925] ---[ end trace 822f779813ab57e1 ]--- [ 151.136624] EIP: sysrq_handle_crash+0x1d/0x30 [ 151.136625] Code: ff eb d6 e8 75 0f ba ff 90 8d 74 26 00 0f 1f 44 00 00 55 89 e5 e8 03 07 c0 ff c7 05 34 72 c1 c1 01 00 00 00 0f ae f8 0f 1f 00 <c6> 05 00 00 00 00 01 5d c3 8d 76 00 8d bc 27 00 00 00 00 0f 1f 44 [ 151.136658] EAX: 00000000 EBX: 0000000a ECX: 00000000 EDX: c1503f70 [ 151.136659] ESI: 00000063 EDI: 00000000 EBP: f36d7e8c ESP: c1c0d87c [ 151.136661] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 [ 151.136662] Kernel panic - not syncing: Fatal exception [ 151.137001] Kernel Offset: disabled [ 151.140587] ---[ end Kernel panic - not syncing: Fatal exception ]--- [ 103.241026] strsep32[2125]: segfault at 4336a7 ip b7df6758 sp bfc73fd0 error 7 in libc-2.26.so[b7d76000+1cd000] [ 103.252505] Code: 1d 83 ec 08 ff 74 24 1c 56 e8 14 d6 ff ff 01 f0 83 c4 10 80 38 00 75 12 c7 03 00 00 00 00 83 c4 04 89 f0 5b 5e c3 8d 74 26 00 <c6> 00 00 83 c0 01 89 03 83 c4 04 89 f0 5b 5e c3 66 90 66 90 66 90 -- 2.13.0
Borislav Petkov
maintainerPATCH 1/9 x86/dumpstack: Remove code_bytes
From: Borislav Petkov <[email protected]>
This was added by
86c418374223 ("[PATCH] i386: add option to show more code in oops reports")
long time ago but experience shows that 64 instruction bytes are plenty when deciphering an oops. So get rid of it.
Removing it will simplify further enhancements to the opcodes dumping machinery coming in the following patches.
Signed-off-by Borislav Petkov <[email protected]>
--- Documentation/admin-guide/kernel-parameters.txt | 5 ----- arch/x86/kernel/dumpstack.c | 27 ++++--------------------- 2 files changed, 4 insertions(+), 28 deletions(-)
Documentation/admin-guide/kernel-parameters.txt +0 -5
@@ -587,11 +587,6 @@ Sets the size of memory pool for coherent, atomic dma allocations, by default set to 256K. - code_bytes [X86] How many bytes of object code to print - in an oops report. - Range: 0 - 8192 - Default: 64 - com20020= [HW,NET] ARCnet - COM20020 chipset Format: <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
arch/x86/kernel/dumpstack.c +4 -23
@@ -22,9 +22,10 @@#include <asm/stacktrace.h> #include <asm/unwind.h> +#define OPCODE_BUFSIZE 64 +int panic_on_unrecovered_nmi;int panic_on_io_nmi; -static unsigned int code_bytes =64 ;static int die_counter; bool in_task_stack(unsigned long *stack, struct task_struct *task,
@@ -356,26 +357,6 @@ void die(const char *str, struct pt_regs *regs, long err)oops_end (flags, regs, sig); } -static int __init code_bytes_setup (char *s) -{ -ssize_t ret; -unsigned long val; - -if (!s) -return -EINVAL ; - - ret =kstrtoul (s,0 , &val); -if (ret) -return ret; - - code_bytes = val; -if (code_bytes >8192 ) - code_bytes =8192 ; - -return 1 ; -} -__setup ("code_bytes=" , code_bytes_setup); -void show_regs (struct pt_regs *regs) {bool all = true;
@@ -393,8 +374,8 @@ void show_regs(struct pt_regs *regs)* time of the fault.. */ if (!user_mode (regs)) { -unsigned int code_prologue = code_bytes *43 /64 ; -unsigned int code_len = code_bytes; +unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; +unsigned int code_len =OPCODE_BUFSIZE ;unsigned char c;u8 *ip;
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Remove code_bytes
x86/dumpstack: Remove code_bytes
Commit-ID: 5d12f0424edf01ccd8abbcba1c7d45fe0b23c779 Gitweb: https://git.kernel.org/tip/5d12f0424edf01ccd8abbcba1c7d45fe0b23c779 Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:16 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:25 +0200
x86/dumpstack: Remove code_bytes
This was added by
86c418374223 ("[PATCH] i386: add option to show more code in oops reports")
long time ago but experience shows that 64 instruction bytes are plenty when deciphering an oops. So get rid of it.
Removing it will simplify further enhancements to the opcodes dumping machinery coming in the following patches.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- Documentation/admin-guide/kernel-parameters.txt | 5 ----- arch/x86/kernel/dumpstack.c | 27 ++++--------------------- 2 files changed, 4 insertions(+), 28 deletions(-)
Documentation/admin-guide/kernel-parameters.txt +0 -5
@@ -587,11 +587,6 @@ Sets the size of memory pool for coherent, atomic dma allocations, by default set to 256K. - code_bytes [X86] How many bytes of object code to print - in an oops report. - Range: 0 - 8192 - Default: 64 - com20020= [HW,NET] ARCnet - COM20020 chipset Format: <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
arch/x86/kernel/dumpstack.c +4 -23
@@ -22,9 +22,10 @@#include <asm/stacktrace.h> #include <asm/unwind.h> +#define OPCODE_BUFSIZE 64 +int panic_on_unrecovered_nmi;int panic_on_io_nmi; -static unsigned int code_bytes =64 ;static int die_counter; bool in_task_stack(unsigned long *stack, struct task_struct *task,
@@ -356,26 +357,6 @@ void die(const char *str, struct pt_regs *regs, long err)oops_end (flags, regs, sig); } -static int __init code_bytes_setup (char *s) -{ -ssize_t ret; -unsigned long val; - -if (!s) -return -EINVAL ; - - ret =kstrtoul (s,0 , &val); -if (ret) -return ret; - - code_bytes = val; -if (code_bytes >8192 ) - code_bytes =8192 ; - -return 1 ; -} -__setup ("code_bytes=" , code_bytes_setup); -void show_regs (struct pt_regs *regs) {bool all = true;
@@ -393,8 +374,8 @@ void show_regs(struct pt_regs *regs)* time of the fault.. */ if (!user_mode (regs)) { -unsigned int code_prologue = code_bytes *43 /64 ; -unsigned int code_len = code_bytes; +unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; +unsigned int code_len =OPCODE_BUFSIZE ;unsigned char c;u8 *ip;
Borislav Petkov
maintainerPATCH 2/9 x86/dumpstack: Unexport oops_begin()
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
The only user outside of arch/ is not a module since
86cd47334b00 ("ACPI, APEI, GHES, Prevent GHES to be built as module")
No functional changes.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/kernel/dumpstack.c | 1 - 1 file changed, 1 deletion(-)
arch/x86/kernel/dumpstack.c +0 -1
@@ -268,7 +268,6 @@ unsigned long oops_begin(void)bust_spinlocks (1 );return flags; } -EXPORT_SYMBOL_GPL (oops_begin);NOKPROBE_SYMBOL (oops_begin);void __noreturn rewind_stack_do_exit (int signr);
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Unexport oops_begin()
x86/dumpstack: Unexport oops_begin()
Commit-ID: 5df61707f0bdf8dce714a14806740e6abf2114c7 Gitweb: https://git.kernel.org/tip/5df61707f0bdf8dce714a14806740e6abf2114c7 Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:17 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:26 +0200
x86/dumpstack: Unexport oops_begin()
The only user outside of arch/ is not a module since
86cd47334b00 ("ACPI, APEI, GHES, Prevent GHES to be built as module")
No functional changes.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/kernel/dumpstack.c | 1 - 1 file changed, 1 deletion(-)
arch/x86/kernel/dumpstack.c +0 -1
@@ -268,7 +268,6 @@ unsigned long oops_begin(void)bust_spinlocks (1 );return flags; } -EXPORT_SYMBOL_GPL (oops_begin);NOKPROBE_SYMBOL (oops_begin);void __noreturn rewind_stack_do_exit (int signr);
Borislav Petkov
maintainerPATCH 3/9 x86/dumpstack: Carve out Code: dumping into a function
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
No functionality change, carve it out into a separate function for later changes.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/kernel/dumpstack.c | 57 ++++++++++++++++++++++++--------------------- 1 file changed, 30 insertions(+), 27 deletions(-)
arch/x86/kernel/dumpstack.c +30 -27
@@ -70,6 +70,35 @@ static void printk_stack_address(unsigned long address, int reliable,printk ("%s %s%pB\n" , log_lvl, reliable ?"" :"? " , (void *)address); } +static void show_opcodes (u8 *rip) +{ +unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; +unsigned int code_len =OPCODE_BUFSIZE ; +unsigned char c; +u8 *ip; +int i; + +printk (KERN_DEFAULT "Code: " ); + + ip = (u8 *)rip - code_prologue; +if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { +/* try starting at IP */ + ip = (u8 *)rip; + code_len = code_len - code_prologue +1 ; + } +for (i =0 ; i < code_len; i++, ip++) { +if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { +pr_cont (" Bad RIP value." ); +break ; + } +if (ip == (u8 *)rip) +pr_cont ("<%02x> " , c); +else +pr_cont ("%02x " , c); + } +pr_cont ("\n" ); +} +void show_iret_regs (struct pt_regs *regs) {printk (KERN_DEFAULT "RIP: %04x:%pS\n" , (int )regs->cs, (void *)regs->ip);
@@ -359,7 +388,6 @@ void die(const char *str, struct pt_regs *regs, long err)void show_regs (struct pt_regs *regs) {bool all = true; -int i;show_regs_print_info (KERN_DEFAULT );
@@ -373,32 +401,7 @@ void show_regs(struct pt_regs *regs)* time of the fault.. */ if (!user_mode (regs)) { -unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; -unsigned int code_len =OPCODE_BUFSIZE ; -unsigned char c; -u8 *ip; -show_trace_log_lvl (current, regs,NULL ,KERN_DEFAULT ); - -printk (KERN_DEFAULT "Code: " ); - - ip = (u8 *)regs->ip - code_prologue; -if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { -/* try starting at IP */ - ip = (u8 *)regs->ip; - code_len = code_len - code_prologue +1 ; - } -for (i =0 ; i < code_len; i++, ip++) { -if (ip < (u8 *)PAGE_OFFSET || -probe_kernel_address (ip, c)) { -pr_cont (" Bad RIP value." ); -break ; - } -if (ip == (u8 *)regs->ip) -pr_cont ("<%02x> " , c); -else -pr_cont ("%02x " , c); - } +show_opcodes ((u8 *)regs->ip); } -pr_cont ("\n" ); }
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Carve out code-dumping into a function
x86/dumpstack: Carve out code-dumping into a function
Commit-ID: f0a1d7c11c3ebe2f601b448d13e7fbc3a0364a03 Gitweb: https://git.kernel.org/tip/f0a1d7c11c3ebe2f601b448d13e7fbc3a0364a03 Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:18 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:26 +0200
x86/dumpstack: Carve out code-dumping into a function
No functionality change, carve it out into a separate function for later changes.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/kernel/dumpstack.c | 57 ++++++++++++++++++++++++--------------------- 1 file changed, 30 insertions(+), 27 deletions(-)
arch/x86/kernel/dumpstack.c +30 -27
@@ -70,6 +70,35 @@ static void printk_stack_address(unsigned long address, int reliable,printk ("%s %s%pB\n" , log_lvl, reliable ?"" :"? " , (void *)address); } +static void show_opcodes (u8 *rip) +{ +unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; +unsigned int code_len =OPCODE_BUFSIZE ; +unsigned char c; +u8 *ip; +int i; + +printk (KERN_DEFAULT "Code: " ); + + ip = (u8 *)rip - code_prologue; +if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { +/* try starting at IP */ + ip = (u8 *)rip; + code_len = code_len - code_prologue +1 ; + } +for (i =0 ; i < code_len; i++, ip++) { +if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { +pr_cont (" Bad RIP value." ); +break ; + } +if (ip == (u8 *)rip) +pr_cont ("<%02x> " , c); +else +pr_cont ("%02x " , c); + } +pr_cont ("\n" ); +} +void show_iret_regs (struct pt_regs *regs) {printk (KERN_DEFAULT "RIP: %04x:%pS\n" , (int )regs->cs, (void *)regs->ip);
@@ -359,7 +388,6 @@ void die(const char *str, struct pt_regs *regs, long err)void show_regs (struct pt_regs *regs) {bool all = true; -int i;show_regs_print_info (KERN_DEFAULT );
@@ -373,32 +401,7 @@ void show_regs(struct pt_regs *regs)* time of the fault.. */ if (!user_mode (regs)) { -unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; -unsigned int code_len =OPCODE_BUFSIZE ; -unsigned char c; -u8 *ip; -show_trace_log_lvl (current, regs,NULL ,KERN_DEFAULT ); - -printk (KERN_DEFAULT "Code: " ); - - ip = (u8 *)regs->ip - code_prologue; -if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { -/* try starting at IP */ - ip = (u8 *)regs->ip; - code_len = code_len - code_prologue +1 ; - } -for (i =0 ; i < code_len; i++, ip++) { -if (ip < (u8 *)PAGE_OFFSET || -probe_kernel_address (ip, c)) { -pr_cont (" Bad RIP value." ); -break ; - } -if (ip == (u8 *)regs->ip) -pr_cont ("<%02x> " , c); -else -pr_cont ("%02x " , c); - } +show_opcodes ((u8 *)regs->ip); } -pr_cont ("\n" ); }
Borislav Petkov
maintainerPATCH 4/9 x86/dumpstack: Improve opcodes dumping in the Code: section
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
The code used to iterate byte-by-byte over the bytes around RIP and that is expensive: disabling pagefaults around it, copy_from_user, etc...
Make it read the whole buffer of OPCODE_BUFSIZE size in one go. Use a statically allocated 64 bytes buffer so that concurrent show_opcodes() do not interleave in the output even though in the majority of the cases we sync on die_lock. Except the #PF path which doesn't...
Also, do the PAGE_OFFSET check outside of the function because latter will be reused in other context.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/kernel/dumpstack.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-)
arch/x86/kernel/dumpstack.c +15 -16
@@ -72,29 +72,24 @@ static void printk_stack_address(unsigned long address, int reliable,static void show_opcodes (u8 *rip) { -unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; -unsigned int code_len =OPCODE_BUFSIZE ; -unsigned char c; +unsigned int code_prologue =OPCODE_BUFSIZE *2 /3 ; +u8 opcodes[OPCODE_BUFSIZE ];u8 *ip;int i;printk (KERN_DEFAULT "Code: " ); ip = (u8 *)rip - code_prologue; -if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { -/* try starting at IP */ - ip = (u8 *)rip; - code_len = code_len - code_prologue +1 ; +if (probe_kernel_read (opcodes, ip,OPCODE_BUFSIZE )) { +pr_cont ("Bad RIP value.\n" ); +return ; } -for (i =0 ; i < code_len; i++, ip++) { -if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { -pr_cont (" Bad RIP value." ); -break ; - } -if (ip == (u8 *)rip) -pr_cont ("<%02x> " , c); + +for (i =0 ; i <OPCODE_BUFSIZE ; i++, ip++) { +if (ip == rip) +pr_cont ("<%02x> " , opcodes[i]);else -pr_cont ("%02x " , c); +pr_cont ("%02x " , opcodes[i]); }pr_cont ("\n" ); }
@@ -402,6 +397,10 @@ void show_regs(struct pt_regs *regs)*/ if (!user_mode (regs)) {show_trace_log_lvl (current, regs,NULL ,KERN_DEFAULT ); -show_opcodes ((u8 *)regs->ip); + +if (regs->ip <PAGE_OFFSET ) +printk (KERN_DEFAULT "Code: Bad RIP value.\n" ); +else +show_opcodes ((u8 *)regs->ip); } }
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Improve opcodes dumping in the code section
x86/dumpstack: Improve opcodes dumping in the code section
Commit-ID: 9e4a90fd34445df64a13d136676a31a4dd22aea3 Gitweb: https://git.kernel.org/tip/9e4a90fd34445df64a13d136676a31a4dd22aea3 Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:19 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:26 +0200
x86/dumpstack: Improve opcodes dumping in the code section
The code used to iterate byte-by-byte over the bytes around RIP and that is expensive: disabling pagefaults around it, copy_from_user, etc...
Make it read the whole buffer of OPCODE_BUFSIZE size in one go. Use a statically allocated 64 bytes buffer so that concurrent show_opcodes() do not interleave in the output even though in the majority of the cases it's serialized via die_lock. Except the #PF path which doesn't...
Also, do the PAGE_OFFSET check outside of the function because latter will be reused in other context.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/kernel/dumpstack.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-)
arch/x86/kernel/dumpstack.c +15 -16
@@ -72,29 +72,24 @@ static void printk_stack_address(unsigned long address, int reliable,static void show_opcodes (u8 *rip) { -unsigned int code_prologue =OPCODE_BUFSIZE *43 /64 ; -unsigned int code_len =OPCODE_BUFSIZE ; -unsigned char c; +unsigned int code_prologue =OPCODE_BUFSIZE *2 /3 ; +u8 opcodes[OPCODE_BUFSIZE ];u8 *ip;int i;printk (KERN_DEFAULT "Code: " ); ip = (u8 *)rip - code_prologue; -if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { -/* try starting at IP */ - ip = (u8 *)rip; - code_len = code_len - code_prologue +1 ; +if (probe_kernel_read (opcodes, ip,OPCODE_BUFSIZE )) { +pr_cont ("Bad RIP value.\n" ); +return ; } -for (i =0 ; i < code_len; i++, ip++) { -if (ip < (u8 *)PAGE_OFFSET ||probe_kernel_address (ip, c)) { -pr_cont (" Bad RIP value." ); -break ; - } -if (ip == (u8 *)rip) -pr_cont ("<%02x> " , c); + +for (i =0 ; i <OPCODE_BUFSIZE ; i++, ip++) { +if (ip == rip) +pr_cont ("<%02x> " , opcodes[i]);else -pr_cont ("%02x " , c); +pr_cont ("%02x " , opcodes[i]); }pr_cont ("\n" ); }
@@ -402,6 +397,10 @@ void show_regs(struct pt_regs *regs)*/ if (!user_mode (regs)) {show_trace_log_lvl (current, regs,NULL ,KERN_DEFAULT ); -show_opcodes ((u8 *)regs->ip); + +if (regs->ip <PAGE_OFFSET ) +printk (KERN_DEFAULT "Code: Bad RIP value.\n" ); +else +show_opcodes ((u8 *)regs->ip); } }
Borislav Petkov
maintainerPATCH 5/9 x86/dumpstack: Add loglevel argument to show_opcodes()
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
Will be used in the next patch.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/include/asm/stacktrace.h | 1 + arch/x86/kernel/dumpstack.c | 6 +++--- 2 files changed, 4 insertions(+), 3 deletions(-)
arch/x86/include/asm/stacktrace.h +1 -0
@@ -111,4 +111,5 @@ static inline unsigned long caller_frame_pointer(void) return (unsigned long)frame; } +void show_opcodes (u8 *rip,const char *loglvl);#endif /* _ASM_X86_STACKTRACE_H */
arch/x86/kernel/dumpstack.c +3 -3
@@ -70,14 +70,14 @@ static void printk_stack_address(unsigned long address, int reliable,printk ("%s %s%pB\n" , log_lvl, reliable ?"" :"? " , (void *)address); } -static void show_opcodes (u8 *rip) +void show_opcodes (u8 *rip,const char *loglvl) {unsigned int code_prologue =OPCODE_BUFSIZE *2 /3 ;u8 opcodes[OPCODE_BUFSIZE ];u8 *ip;int i; -printk (KERN_DEFAULT "Code: " ); +printk ("%sCode: " , loglvl); ip = (u8 *)rip - code_prologue;if (probe_kernel_read (opcodes, ip,OPCODE_BUFSIZE )) {
@@ -401,6 +401,6 @@ void show_regs(struct pt_regs *regs)if (regs->ip <PAGE_OFFSET )printk (KERN_DEFAULT "Code: Bad RIP value.\n" );else -show_opcodes ((u8 *)regs->ip); +show_opcodes ((u8 *)regs->ip,KERN_DEFAULT ); } }
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Add loglevel argument to show_opcodes()
x86/dumpstack: Add loglevel argument to show_opcodes()
Commit-ID: e8b6f984516b1fcb0ccf4469ca42777c9c2dc76d Gitweb: https://git.kernel.org/tip/e8b6f984516b1fcb0ccf4469ca42777c9c2dc76d Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:20 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:26 +0200
x86/dumpstack: Add loglevel argument to show_opcodes()
Will be used in the next patch.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/include/asm/stacktrace.h | 1 + arch/x86/kernel/dumpstack.c | 6 +++--- 2 files changed, 4 insertions(+), 3 deletions(-)
arch/x86/include/asm/stacktrace.h +1 -0
@@ -111,4 +111,5 @@ static inline unsigned long caller_frame_pointer(void) return (unsigned long)frame; } +void show_opcodes (u8 *rip,const char *loglvl);#endif /* _ASM_X86_STACKTRACE_H */
arch/x86/kernel/dumpstack.c +3 -3
@@ -70,14 +70,14 @@ static void printk_stack_address(unsigned long address, int reliable,printk ("%s %s%pB\n" , log_lvl, reliable ?"" :"? " , (void *)address); } -static void show_opcodes (u8 *rip) +void show_opcodes (u8 *rip,const char *loglvl) {unsigned int code_prologue =OPCODE_BUFSIZE *2 /3 ;u8 opcodes[OPCODE_BUFSIZE ];u8 *ip;int i; -printk (KERN_DEFAULT "Code: " ); +printk ("%sCode: " , loglvl); ip = (u8 *)rip - code_prologue;if (probe_kernel_read (opcodes, ip,OPCODE_BUFSIZE )) {
@@ -401,6 +401,6 @@ void show_regs(struct pt_regs *regs)if (regs->ip <PAGE_OFFSET )printk (KERN_DEFAULT "Code: Bad RIP value.\n" );else -show_opcodes ((u8 *)regs->ip); +show_opcodes ((u8 *)regs->ip,KERN_DEFAULT ); } }
Borislav Petkov
maintainerPATCH 6/9 x86/fault: Dump user opcode bytes on fatal faults
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
Sometimes it is useful to see which user opcode bytes RIP points to when a fault happens: be it to rule out RIP corruption, to dump info early during boot, when doing core dumps is impossible due to not having writable fs yet.
Sometimes it is useful if debugging an issue and one doesn't have access to the executable which caused the fault in order to disassemble it.
That last aspect might have some security implications so show_unhandled_signals could be revisited for that or a new config option added.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/mm/fault.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
arch/x86/mm/fault.c +5 -2
@@ -828,6 +828,8 @@ static inline void show_signal_msg(struct pt_regs *regs, unsigned long error_code, unsigned long address, struct task_struct *tsk) { + const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; +if (!unhandled_signal (tsk,SIGSEGV ))return ;
@@ -835,13 +837,14 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,return ;printk ("%s%s[%d]: segfault at %lx ip %px sp %px error %lx" , -task_pid_nr (tsk) >1 ?KERN_INFO :KERN_EMERG , - tsk->comm,task_pid_nr (tsk), address, + loglvl, tsk->comm,task_pid_nr (tsk), address, (void *)regs->ip, (void *)regs->sp, error_code);print_vma_addr (KERN_CONT " in " , regs->ip);printk (KERN_CONT "\n" ); + +show_opcodes ((u8 *)regs->ip, loglvl); } static void
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/fault: Dump user opcode bytes on fatal faults
x86/fault: Dump user opcode bytes on fatal faults
Commit-ID: ba54d856a9d8a9c56b87e20c88602b7e3cb568fb Gitweb: https://git.kernel.org/tip/ba54d856a9d8a9c56b87e20c88602b7e3cb568fb Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:21 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:27 +0200
x86/fault: Dump user opcode bytes on fatal faults
Sometimes it is useful to see which user opcode bytes RIP points to when a fault happens: be it to rule out RIP corruption, to dump info early during boot, when doing core dumps is impossible due to not having a writable filesystem yet.
Sometimes it is useful if debugging an issue and one doesn't have access to the executable which caused the fault in order to disassemble it.
That last aspect might have some security implications so show_unhandled_signals could be revisited for that or a new config option added.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/mm/fault.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
arch/x86/mm/fault.c +5 -2
@@ -828,6 +828,8 @@ static inline void show_signal_msg(struct pt_regs *regs, unsigned long error_code, unsigned long address, struct task_struct *tsk) { + const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; +if (!unhandled_signal (tsk,SIGSEGV ))return ;
@@ -835,13 +837,14 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,return ;printk ("%s%s[%d]: segfault at %lx ip %px sp %px error %lx" , -task_pid_nr (tsk) >1 ?KERN_INFO :KERN_EMERG , - tsk->comm,task_pid_nr (tsk), address, + loglvl, tsk->comm,task_pid_nr (tsk), address, (void *)regs->ip, (void *)regs->sp, error_code);print_vma_addr (KERN_CONT " in " , regs->ip);printk (KERN_CONT "\n" ); + +show_opcodes ((u8 *)regs->ip, loglvl); } static void
Borislav Petkov
maintainerPATCH 7/9 x86/dumpstack: Add a show_ip() function
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
... which shows the Instruction Pointer along with the insn bytes around it. Use it whenever we print rIP. Drop the rIP < PAGE_OFFSET check since our probe_kernel_read() can handle any address properly.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/include/asm/stacktrace.h | 1 + arch/x86/kernel/dumpstack.c | 23 +++++++++++++---------- arch/x86/kernel/process_32.c | 8 +++----- 3 files changed, 17 insertions(+), 15 deletions(-)
arch/x86/include/asm/stacktrace.h +1 -0
@@ -112,4 +112,5 @@ static inline unsigned long caller_frame_pointer(void) }void show_opcodes (u8 *rip,const char *loglvl); +void show_ip (struct pt_regs *regs,const char *loglvl);#endif /* _ASM_X86_STACKTRACE_H */
arch/x86/kernel/dumpstack.c +13 -10
@@ -94,9 +94,19 @@ void show_opcodes(u8 *rip, const char *loglvl)pr_cont ("\n" ); } +void show_ip (struct pt_regs *regs,const char *loglvl) +{ +#ifdef CONFIG_X86_32 +printk ("%sEIP: %pS\n" , loglvl, (void *)regs->ip); +#else +printk ("%sRIP: %04x:%pS\n" , loglvl, (int )regs->cs, (void *)regs->ip); +#endif +show_opcodes ((u8 *)regs->ip, loglvl); +} +void show_iret_regs (struct pt_regs *regs) { -printk (KERN_DEFAULT "RIP: %04x:%pS\n" , (int )regs->cs, (void *)regs->ip); +show_ip (regs,KERN_DEFAULT );printk (KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx" , (int )regs->ss, regs->sp, regs->flags); }
@@ -392,15 +402,8 @@ void show_regs(struct pt_regs *regs)__show_regs (regs, all);/* -* When in-kernel, we also print out the stack and code at the -* time of the fault.. +* When in-kernel, we also print out the stack at the time of the fault.. */ -if (!user_mode (regs)) { +if (!user_mode (regs))show_trace_log_lvl (current, regs,NULL ,KERN_DEFAULT ); - -if (regs->ip <PAGE_OFFSET ) -printk (KERN_DEFAULT "Code: Bad RIP value.\n" ); -else -show_opcodes ((u8 *)regs->ip,KERN_DEFAULT ); - } }
arch/x86/kernel/process_32.c +3 -5
@@ -76,16 +76,14 @@ void __show_regs(struct pt_regs *regs, int all)savesegment (gs, gs); } -printk (KERN_DEFAULT "EIP: %pS\n" , (void *)regs->ip); -printk (KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n" , regs->flags, -raw_smp_processor_id ()); +show_ip (regs,KERN_DEFAULT );printk (KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n" , regs->ax, regs->bx, regs->cx, regs->dx);printk (KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n" , regs->si, regs->di, regs->bp, sp); -printk (KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n" , - (u16 )regs->ds, (u16 )regs->es, (u16 )regs->fs, gs, ss); +printk (KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n" , + (u16 )regs->ds, (u16 )regs->es, (u16 )regs->fs, gs, ss, regs->flags);if (!all)return ;
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Add a show_ip() function
x86/dumpstack: Add a show_ip() function
Commit-ID: 7cccf0725cf7402514e09c52b089430005798b7f Gitweb: https://git.kernel.org/tip/7cccf0725cf7402514e09c52b089430005798b7f Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:22 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:27 +0200
x86/dumpstack: Add a show_ip() function
... which shows the Instruction Pointer along with the insn bytes around it. Use it whenever rIP is printed. Drop the rIP < PAGE_OFFSET check since probe_kernel_read() can handle any address properly.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/include/asm/stacktrace.h | 1 + arch/x86/kernel/dumpstack.c | 23 +++++++++++++---------- arch/x86/kernel/process_32.c | 8 +++----- 3 files changed, 17 insertions(+), 15 deletions(-)
arch/x86/include/asm/stacktrace.h +1 -0
@@ -112,4 +112,5 @@ static inline unsigned long caller_frame_pointer(void) }void show_opcodes (u8 *rip,const char *loglvl); +void show_ip (struct pt_regs *regs,const char *loglvl);#endif /* _ASM_X86_STACKTRACE_H */
arch/x86/kernel/dumpstack.c +13 -10
@@ -94,9 +94,19 @@ void show_opcodes(u8 *rip, const char *loglvl)pr_cont ("\n" ); } +void show_ip (struct pt_regs *regs,const char *loglvl) +{ +#ifdef CONFIG_X86_32 +printk ("%sEIP: %pS\n" , loglvl, (void *)regs->ip); +#else +printk ("%sRIP: %04x:%pS\n" , loglvl, (int )regs->cs, (void *)regs->ip); +#endif +show_opcodes ((u8 *)regs->ip, loglvl); +} +void show_iret_regs (struct pt_regs *regs) { -printk (KERN_DEFAULT "RIP: %04x:%pS\n" , (int )regs->cs, (void *)regs->ip); +show_ip (regs,KERN_DEFAULT );printk (KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx" , (int )regs->ss, regs->sp, regs->flags); }
@@ -392,15 +402,8 @@ void show_regs(struct pt_regs *regs)__show_regs (regs, all);/* -* When in-kernel, we also print out the stack and code at the -* time of the fault.. +* When in-kernel, we also print out the stack at the time of the fault.. */ -if (!user_mode (regs)) { +if (!user_mode (regs))show_trace_log_lvl (current, regs,NULL ,KERN_DEFAULT ); - -if (regs->ip <PAGE_OFFSET ) -printk (KERN_DEFAULT "Code: Bad RIP value.\n" ); -else -show_opcodes ((u8 *)regs->ip,KERN_DEFAULT ); - } }
arch/x86/kernel/process_32.c +3 -5
@@ -76,16 +76,14 @@ void __show_regs(struct pt_regs *regs, int all)savesegment (gs, gs); } -printk (KERN_DEFAULT "EIP: %pS\n" , (void *)regs->ip); -printk (KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n" , regs->flags, -raw_smp_processor_id ()); +show_ip (regs,KERN_DEFAULT );printk (KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n" , regs->ax, regs->bx, regs->cx, regs->dx);printk (KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n" , regs->si, regs->di, regs->bp, sp); -printk (KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n" , - (u16 )regs->ds, (u16 )regs->es, (u16 )regs->fs, gs, ss); +printk (KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n" , + (u16 )regs->ds, (u16 )regs->es, (u16 )regs->fs, gs, ss, regs->flags);if (!all)return ;
Borislav Petkov
maintainerPATCH 8/9 x86/dumpstack: Save first regs set for the executive summary
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
Save the regs set when we call __die() for the first time and print it in oops_end().
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/kernel/dumpstack.c | 32 ++++++++++++-------------------- 1 file changed, 12 insertions(+), 20 deletions(-)
arch/x86/kernel/dumpstack.c +12 -20
@@ -28,6 +28,8 @@ int panic_on_unrecovered_nmi;int panic_on_io_nmi;static int die_counter; +static struct pt_regs exec_summary_regs; +bool in_task_stack (unsigned long *stack,struct task_struct *task,struct stack_info *info) {
@@ -321,6 +323,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)raw_local_irq_restore (flags);oops_exit (); +/* Executive summary in case the oops scrolled away */ +__show_regs (&exec_summary_regs, true); +if (!signr)return ;if (in_interrupt ())
@@ -339,10 +344,10 @@ NOKPROBE_SYMBOL(oops_end);int __die (const char *str,struct pt_regs *regs,long err) { -#ifdef CONFIG_X86_32 -unsigned short ss; -unsigned long sp; -#endif +/* Save the regs of the first oops for the executive summary later. */ +if (!die_counter) + exec_summary_regs = *regs; + printk(KERN_DEFAULT "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter, IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",
@@ -352,26 +357,13 @@ int __die(const char *str, struct pt_regs *regs, long err)IS_ENABLED (CONFIG_PAGE_TABLE_ISOLATION ) ? (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : ""); +show_regs (regs); +print_modules (); +if (notify_die (DIE_OOPS , str, regs, err, current->thread.trap_nr,SIGSEGV ) ==NOTIFY_STOP )return 1 ; -print_modules (); -show_regs (regs); -#ifdef CONFIG_X86_32 -if (user_mode (regs)) { - sp = regs->sp; - ss = regs->ss; - }else { - sp =kernel_stack_pointer (regs); -savesegment (ss, ss); - } -printk (KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n" , - (void *)regs->ip, ss, sp); -#else -/* Executive summary in case the oops scrolled away */ -printk (KERN_ALERT "RIP: %pS RSP: %016lx\n" , (void *)regs->ip, regs->sp); -#endif return 0 ; }NOKPROBE_SYMBOL (__die);
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Save first regs set for the executive summary
x86/dumpstack: Save first regs set for the executive summary
Commit-ID: 602bd705da334f214fc03db328dc37d2f1f33307 Gitweb: https://git.kernel.org/tip/602bd705da334f214fc03db328dc37d2f1f33307 Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:23 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:28 +0200
x86/dumpstack: Save first regs set for the executive summary
Save the regs set when __die() is onvoked for the first time and print it in oops_end().
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/kernel/dumpstack.c | 32 ++++++++++++-------------------- 1 file changed, 12 insertions(+), 20 deletions(-)
arch/x86/kernel/dumpstack.c +12 -20
@@ -28,6 +28,8 @@ int panic_on_unrecovered_nmi;int panic_on_io_nmi;static int die_counter; +static struct pt_regs exec_summary_regs; +bool in_task_stack (unsigned long *stack,struct task_struct *task,struct stack_info *info) {
@@ -321,6 +323,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)raw_local_irq_restore (flags);oops_exit (); +/* Executive summary in case the oops scrolled away */ +__show_regs (&exec_summary_regs, true); +if (!signr)return ;if (in_interrupt ())
@@ -339,10 +344,10 @@ NOKPROBE_SYMBOL(oops_end);int __die (const char *str,struct pt_regs *regs,long err) { -#ifdef CONFIG_X86_32 -unsigned short ss; -unsigned long sp; -#endif +/* Save the regs of the first oops for the executive summary later. */ +if (!die_counter) + exec_summary_regs = *regs; + printk(KERN_DEFAULT "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter, IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",
@@ -352,26 +357,13 @@ int __die(const char *str, struct pt_regs *regs, long err)IS_ENABLED (CONFIG_PAGE_TABLE_ISOLATION ) ? (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : ""); +show_regs (regs); +print_modules (); +if (notify_die (DIE_OOPS , str, regs, err, current->thread.trap_nr,SIGSEGV ) ==NOTIFY_STOP )return 1 ; -print_modules (); -show_regs (regs); -#ifdef CONFIG_X86_32 -if (user_mode (regs)) { - sp = regs->sp; - ss = regs->ss; - }else { - sp =kernel_stack_pointer (regs); -savesegment (ss, ss); - } -printk (KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n" , - (void *)regs->ip, ss, sp); -#else -/* Executive summary in case the oops scrolled away */ -printk (KERN_ALERT "RIP: %pS RSP: %016lx\n" , (void *)regs->ip, regs->sp); -#endif return 0 ; }NOKPROBE_SYMBOL (__die);
Borislav Petkov
maintainerPATCH 9/9 x86/dumpstack: Explain the reasoning for the prologue and buffer size
In reply to Borislav PetkovFrom: Borislav Petkov <[email protected]>
The whole reasoning behind the amount of opcode bytes dumped and prologue length isn't very clear so let's hold down some of the reasons for why it is done the way it is.
Signed-off-by Borislav Petkov <[email protected]>
--- arch/x86/kernel/dumpstack.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
arch/x86/kernel/dumpstack.c +19 -0
@@ -72,6 +72,25 @@ static void printk_stack_address(unsigned long address, int reliable,printk ("%s %s%pB\n" , log_lvl, reliable ?"" :"? " , (void *)address); } +/* +* There are a couple of reasons for the 2/3rd prologue, courtesy of Linus: +* +* In case where we don't have the exact kernel image (which, if we did, we can +* simply disassemble and navigate to the RIP), the purpose of the bigger +* prologue is to have more context and to be able to correlate the code from +* the different toolchains better. +* +* In addition, it helps in recreating the register allocation of the failing +* kernel and thus make sense of the register dump. +* +* What is more, the additional complication of a variable length insn arch like +* x86 warrants having longer byte sequence before rIP so that the disassembler +* can "sync" up properly and find instruction boundaries when decoding the +* opcode bytes. +* +* Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random +* guesstimate in attempt to achieve all of the above. +*/ void show_opcodes (u8 *rip,const char *loglvl) {unsigned int code_prologue =OPCODE_BUFSIZE *2 /3 ;
Signature · 1 line
2.13.0
tip-bot for Borislav Petkov
merge bot[tip:x86/cleanups] x86/dumpstack: Explain the reasoning for the prologue and buffer size
x86/dumpstack: Explain the reasoning for the prologue and buffer size
Commit-ID: 4dba072cd097f35fa8f77c49d909ada2b079a4c4 Gitweb: https://git.kernel.org/tip/4dba072cd097f35fa8f77c49d909ada2b079a4c4 Author: Borislav Petkov <[email protected]> AuthorDate: Tue, 17 Apr 2018 18:11:24 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Thu, 26 Apr 2018 16:15:28 +0200
x86/dumpstack: Explain the reasoning for the prologue and buffer size
The whole reasoning behind the amount of opcode bytes dumped and prologue length isn't very clear so write down some of the reasons for why it is done the way it is.
Signed-off-by Borislav Petkov <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Andy Lutomirski <[email protected]>
--- arch/x86/kernel/dumpstack.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
arch/x86/kernel/dumpstack.c +19 -0
@@ -72,6 +72,25 @@ static void printk_stack_address(unsigned long address, int reliable,printk ("%s %s%pB\n" , log_lvl, reliable ?"" :"? " , (void *)address); } +/* +* There are a couple of reasons for the 2/3rd prologue, courtesy of Linus: +* +* In case where we don't have the exact kernel image (which, if we did, we can +* simply disassemble and navigate to the RIP), the purpose of the bigger +* prologue is to have more context and to be able to correlate the code from +* the different toolchains better. +* +* In addition, it helps in recreating the register allocation of the failing +* kernel and thus make sense of the register dump. +* +* What is more, the additional complication of a variable length insn arch like +* x86 warrants having longer byte sequence before rIP so that the disassembler +* can "sync" up properly and find instruction boundaries when decoding the +* opcode bytes. +* +* Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random +* guesstimate in attempt to achieve all of the above. +*/ void show_opcodes (u8 *rip,const char *loglvl) {unsigned int code_prologue =OPCODE_BUFSIZE *2 /3 ;