FAILED: patch "[PATCH] powerpc/ftrace: Create a dummy stackframe to fix stack unwind" failed to apply to 4.14-stable tree
Subsystems (3)
[email protected]
maintainerThe patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y
git checkout FETCH_HEAD
git cherry-pick -x 41a506ef71eb38d94fe133f565c87c3e06ccc072
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023080741-polka-twice-b0df@gregkh' --subject-prefix 'PATCH 4.14.y' HEAD^..
Possible dependencies:
41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind") a5f04d1f2724 ("powerpc/ftrace: Regroup PPC64 specific operations in ftrace_mprofile.S") 228216716cb5 ("powerpc/ftrace: Refactor ftrace_{regs_}caller")9bdb2eec3dde ("powerpc/ftrace: Don't use lmw/stmw in ftrace_regs_caller()") 76b372814b08 ("powerpc/ftrace: Style cleanup in ftrace_mprofile.S")fc75f8733798 ("powerpc/ftrace: Have arch_ftrace_get_regs() return NULL unless FL_SAVE_REGS is set") 34d8dac807f0 ("powerpc/ftrace: Also save r1 in ftrace_caller()")4ee83a2cfbc4 ("powerpc/ftrace: Remove ftrace_32.S")41315494beed ("powerpc/ftrace: Prepare ftrace_64_mprofile.S for reuse by PPC32") 830213786c49 ("powerpc/ftrace: directly call of function graph tracer by ftrace caller") 0c81ed5ed438 ("powerpc/ftrace: Refactor ftrace_{en/dis}able_ftrace_graph_caller") 40b035efe288 ("powerpc/ftrace: Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS") c75388a8ceff ("powerpc/ftrace: Prepare PPC64's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS") d95bf254be5f ("powerpc/ftrace: Prepare PPC32's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS") 7bdb478c1d15 ("powerpc/ftrace: Simplify PPC32's return_to_handler()")7875bc9b07cd ("powerpc/ftrace: Don't save again LR in ftrace_regs_caller() on PPC32") c545b9f040f3 ("powerpc/inst: Define ppc_inst_t")aebd1fb45c62 ("powerpc: flexible GPR range save/restore macros")7dfbfb87c243 ("powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32") c93d4f6ecf4b ("powerpc/ftrace: Add module_trampoline_target() for PPC32")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 41a506ef71eb38d94fe133f565c87c3e06ccc072 Mon Sep 17 00:00:00 2001
From: Naveen N Rao <[email protected]>
Date: Wed, 21 Jun 2023 10:43:49 +0530
Subject: [PATCH] powerpc/ftrace: Create a dummy stackframe to fix stack unwind
With ppc64 -mprofile-kernel and ppc32 -pg, profiling instructions to call into ftrace are emitted right at function entry. The instruction sequence used is minimal to reduce overhead. Crucially, a stackframe is not created for the function being traced. This breaks stack unwinding since the function being traced does not have a stackframe for itself. As such, it never shows up in the backtrace:
/sys/kernel/debug/tracing # echo 1 > /proc/sys/kernel/stack_tracer_enabled /sys/kernel/debug/tracing # cat stack_trace
Depth Size Location (17 entries)
----- ---- --------
0) 4144 32 ftrace_call+0x4/0x44
1) 4112 432 get_page_from_freelist+0x26c/0x1ad0
2) 3680 496 __alloc_pages+0x290/0x1280
3) 3184 336 __folio_alloc+0x34/0x90
4) 2848 176 vma_alloc_folio+0xd8/0x540
5) 2672 272 __handle_mm_fault+0x700/0x1cc0
6) 2400 208 handle_mm_fault+0xf0/0x3f0
7) 2192 80 ___do_page_fault+0x3e4/0xbe0
8) 2112 160 do_page_fault+0x30/0xc0
9) 1952 256 data_access_common_virt+0x210/0x220
10) 1696 400 0xc00000000f16b100
11) 1296 384 load_elf_binary+0x804/0x1b80
12) 912 208 bprm_execve+0x2d8/0x7e0
13) 704 64 do_execveat_common+0x1d0/0x2f0
14) 640 160 sys_execve+0x54/0x70
15) 480 64 system_call_exception+0x138/0x350
16) 416 416 system_call_common+0x160/0x2c4Fix this by having ftrace create a dummy stackframe for the function being traced. With this, backtraces now capture the function being traced:
/sys/kernel/debug/tracing # cat stack_trace
Depth Size Location (17 entries)
----- ---- --------
0) 3888 32 _raw_spin_trylock+0x8/0x70
1) 3856 576 get_page_from_freelist+0x26c/0x1ad0
2) 3280 64 __alloc_pages+0x290/0x1280
3) 3216 336 __folio_alloc+0x34/0x90
4) 2880 176 vma_alloc_folio+0xd8/0x540
5) 2704 416 __handle_mm_fault+0x700/0x1cc0
6) 2288 96 handle_mm_fault+0xf0/0x3f0
7) 2192 48 ___do_page_fault+0x3e4/0xbe0
8) 2144 192 do_page_fault+0x30/0xc0
9) 1952 608 data_access_common_virt+0x210/0x220
10) 1344 16 0xc0000000334bbb50
11) 1328 416 load_elf_binary+0x804/0x1b80
12) 912 64 bprm_execve+0x2d8/0x7e0
13) 848 176 do_execveat_common+0x1d0/0x2f0
14) 672 192 sys_execve+0x54/0x70
15) 480 64 system_call_exception+0x138/0x350
16) 416 416 system_call_common+0x160/0x2c4This results in two additional stores in the ftrace entry code, but produces reliable backtraces.
arch/powerpc/kernel/trace/ftrace_mprofile.S +7 -2
@@ -33,6 +33,9 @@ * and then arrange for the ftrace function to be called. */ .macro ftrace_regs_entry allregs + /* Create a minimal stack frame for representing B */ + PPC_STLU r1, -STACK_FRAME_MIN_SIZE(r1) + /* Create our stack frame + pt_regs */ PPC_STLU r1,-SWITCH_FRAME_SIZE(r1)
@@ -42,7 +45,7 @@ #ifdef CONFIG_PPC64 /* Save the original return address in A's stack frame */ - std r0, LRSAVE+SWITCH_FRAME_SIZE(r1) + std r0, LRSAVE+SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE(r1) /* Ok to continue? */ lbz r3, PACA_FTRACE_ENABLED(r13) cmpdi r3, 0
@@ -77,6 +80,8 @@ mflr r7 /* Save it as pt_regs->nip */ PPC_STL r7, _NIP(r1) + /* Also save it in B's stackframe header for proper unwind */ + PPC_STL r7, LRSAVE+SWITCH_FRAME_SIZE(r1) /* Save the read LR in pt_regs->link */ PPC_STL r0, _LINK(r1)
@@ -142,7 +147,7 @@ #endif /* Pop our stack frame */ - addi r1, r1, SWITCH_FRAME_SIZE + addi r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE #ifdef CONFIG_LIVEPATCH_64 /* Based on the cmpd above, if the NIP was altered handle livepatch */
PATCH 1/2 powerpc/ftrace: Create a dummy stackframe to fix stack unwind
commit 41a506ef71eb38d94fe133f565c87c3e06ccc072 upstream.
With ppc64 -mprofile-kernel and ppc32 -pg, profiling instructions to call into ftrace are emitted right at function entry. The instruction sequence used is minimal to reduce overhead. Crucially, a stackframe is not created for the function being traced. This breaks stack unwinding since the function being traced does not have a stackframe for itself. As such, it never shows up in the backtrace:
/sys/kernel/debug/tracing # echo 1 > /proc/sys/kernel/stack_tracer_enabled /sys/kernel/debug/tracing # cat stack_trace
Depth Size Location (17 entries)
----- ---- --------
0) 4144 32 ftrace_call+0x4/0x44
1) 4112 432 get_page_from_freelist+0x26c/0x1ad0
2) 3680 496 __alloc_pages+0x290/0x1280
3) 3184 336 __folio_alloc+0x34/0x90
4) 2848 176 vma_alloc_folio+0xd8/0x540
5) 2672 272 __handle_mm_fault+0x700/0x1cc0
6) 2400 208 handle_mm_fault+0xf0/0x3f0
7) 2192 80 ___do_page_fault+0x3e4/0xbe0
8) 2112 160 do_page_fault+0x30/0xc0
9) 1952 256 data_access_common_virt+0x210/0x220
10) 1696 400 0xc00000000f16b100
11) 1296 384 load_elf_binary+0x804/0x1b80
12) 912 208 bprm_execve+0x2d8/0x7e0
13) 704 64 do_execveat_common+0x1d0/0x2f0
14) 640 160 sys_execve+0x54/0x70
15) 480 64 system_call_exception+0x138/0x350
16) 416 416 system_call_common+0x160/0x2c4Fix this by having ftrace create a dummy stackframe for the function being traced. With this, backtraces now capture the function being traced:
/sys/kernel/debug/tracing # cat stack_trace
Depth Size Location (17 entries)
----- ---- --------
0) 3888 32 _raw_spin_trylock+0x8/0x70
1) 3856 576 get_page_from_freelist+0x26c/0x1ad0
2) 3280 64 __alloc_pages+0x290/0x1280
3) 3216 336 __folio_alloc+0x34/0x90
4) 2880 176 vma_alloc_folio+0xd8/0x540
5) 2704 416 __handle_mm_fault+0x700/0x1cc0
6) 2288 96 handle_mm_fault+0xf0/0x3f0
7) 2192 48 ___do_page_fault+0x3e4/0xbe0
8) 2144 192 do_page_fault+0x30/0xc0
9) 1952 608 data_access_common_virt+0x210/0x220
10) 1344 16 0xc0000000334bbb50
11) 1328 416 load_elf_binary+0x804/0x1b80
12) 912 64 bprm_execve+0x2d8/0x7e0
13) 848 176 do_execveat_common+0x1d0/0x2f0
14) 672 192 sys_execve+0x54/0x70
15) 480 64 system_call_exception+0x138/0x350
16) 416 416 system_call_common+0x160/0x2c4This results in two additional stores in the ftrace entry code, but produces reliable backtraces.
--- arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
arch/powerpc/kernel/trace/ftrace_64_mprofile.S +6 -1
@@ -41,6 +41,9 @@ _GLOBAL(ftrace_caller) /* Save the original return address in A's stack frame */ std r0,LRSAVE(r1) + /* Create a minimal stack frame for representing B */ + stdu r1, -STACK_FRAME_MIN_SIZE(r1) + /* Create our stack frame + pt_regs */ stdu r1,-SWITCH_FRAME_SIZE(r1)
@@ -64,6 +67,8 @@ _GLOBAL(ftrace_caller) mflr r7 /* Save it as pt_regs->nip */ std r7, _NIP(r1) + /* Also save it in B's stackframe header for proper unwind */ + std r7, LRSAVE+SWITCH_FRAME_SIZE(r1) /* Save the read LR in pt_regs->link */ std r0, _LINK(r1)
@@ -146,7 +151,7 @@ ftrace_call: ld r2, 24(r1) /* Pop our stack frame */ - addi r1, r1, SWITCH_FRAME_SIZE + addi r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE #ifdef CONFIG_LIVEPATCH /*
base-commit: 27972f32764632d687a5f851c1ce5e206a09acce
Signature · 1 line
2.43.0
PATCH 2/2 powerpc/ftrace: Fix stack teardown in ftrace_no_trace
commit 4b3338aaa74d7d4ec5b6734dc298f0db94ec83d2 upstream.
Commit 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind") added use of a new stack frame on ftrace entry to fix stack unwind. However, the commit missed updating the offset used while tearing down the ftrace stack when ftrace is disabled. Fix the same.
In addition, the commit missed saving the correct stack pointer in pt_regs. Update the same.
--- arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/powerpc/kernel/trace/ftrace_64_mprofile.S +1 -1
@@ -54,7 +54,7 @@ _GLOBAL(ftrace_caller) SAVE_10GPRS(22, r1) /* Save previous stack pointer (r1) */ - addi r8, r1, SWITCH_FRAME_SIZE + addi r8, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE std r8, GPR1(r1) /* Load special regs for save below */
Signature · 1 line
2.43.0