x86-64: Use normal ptregs stub for execve
PATCH 1/1 x86-64: Use normal ptregs stub for execve
Execve historically passed regs by value, so it had a seperate stub. This is no longer true, so change it to use a normal PTREGSCALL stub.
--- arch/x86/kernel/entry_64.S | 17 +---------------- 1 files changed, 1 insertions(+), 16 deletions(-)
arch/x86/kernel/entry_64.S +1 -16
@@ -696,6 +696,7 @@ END(\label) PTREGSCALL stub_clone, sys_clone, %r8 PTREGSCALL stub_fork, sys_fork, %rdi PTREGSCALL stub_vfork, sys_vfork, %rdi + PTREGSCALL stub_execve, sys_execve, %rcx PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx PTREGSCALL stub_iopl, sys_iopl, %rsi
@@ -712,22 +713,6 @@ ENTRY(ptregscall_common) CFI_ENDPROC END(ptregscall_common) -ENTRY(stub_execve) - CFI_STARTPROC - popq %r11 - CFI_ADJUST_CFA_OFFSET -8 - CFI_REGISTER rip, r11 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 - movq %rsp, %rcx - call sys_execve - RESTORE_TOP_OF_STACK %r11 - movq %rax,RAX(%rsp) - RESTORE_REST - jmp int_ret_from_sys_call - CFI_ENDPROC -END(stub_execve) - /* * sigreturn is special because it needs to restore all registers on return. * This cannot be done with SYSRET, so use the IRET return path instead.
Signature · 1 line
1.6.6
Commit-ID: f19a25c872b20ae4357f72687cf3e7b0da220ee2 Gitweb: http://git.kernel.org/tip/f19a25c872b20ae4357f72687cf3e7b0da220ee2 Author: Brian Gerst <[email protected]> AuthorDate: Mon, 25 Jan 2010 10:47:33 -0500 Committer: H. Peter Anvin <[email protected]> CommitDate: Tue, 26 Jan 2010 23:38:14 -0800
x86-64: Use normal ptregs stub for execve
Execve historically passed regs by value, so it had a seperate stub. This is no longer true, so change it to use a normal PTREGSCALL stub.
LKML-Reference: <[email protected]>
--- arch/x86/kernel/entry_64.S | 17 +---------------- 1 files changed, 1 insertions(+), 16 deletions(-)
arch/x86/kernel/entry_64.S +1 -16
@@ -696,6 +696,7 @@ END(\label) PTREGSCALL stub_clone, sys_clone, %r8 PTREGSCALL stub_fork, sys_fork, %rdi PTREGSCALL stub_vfork, sys_vfork, %rdi + PTREGSCALL stub_execve, sys_execve, %rcx PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx PTREGSCALL stub_iopl, sys_iopl, %rsi
@@ -712,22 +713,6 @@ ENTRY(ptregscall_common) CFI_ENDPROC END(ptregscall_common) -ENTRY(stub_execve) - CFI_STARTPROC - popq %r11 - CFI_ADJUST_CFA_OFFSET -8 - CFI_REGISTER rip, r11 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 - movq %rsp, %rcx - call sys_execve - RESTORE_TOP_OF_STACK %r11 - movq %rax,RAX(%rsp) - RESTORE_REST - jmp int_ret_from_sys_call - CFI_ENDPROC -END(stub_execve) - /* * sigreturn is special because it needs to restore all registers on return. * This cannot be done with SYSRET, so use the IRET return path instead.
Quoted 12 lines · tip-bot for Brian Gerst
Commit-ID: f19a25c872b20ae4357f72687cf3e7b0da220ee2 Gitweb: http://git.kernel.org/tip/f19a25c872b20ae4357f72687cf3e7b0da220ee2 Author: Brian Gerst <[email protected]> AuthorDate: Mon, 25 Jan 2010 10:47:33 -0500 Committer: H. Peter Anvin <[email protected]> CommitDate: Tue, 26 Jan 2010 23:38:14 -0800x86-64: Use normal ptregs stub for execve
Execve historically passed regs by value, so it had a seperate stub. This is no longer true, so change it to use a normal PTREGSCALL stub.
Quoted 6 lines
Signed-off-by Brian Gerst <[email protected]>LKML-Reference: <[email protected]>
Signed-off-by H. Peter Anvin <[email protected]>--- arch/x86/kernel/entry_64.S | 17 +---------------- 1 files changed, 1 insertions(+), 16 deletions(-)
FYI, -tip testing found that this commit breaks the grub binary on 64-bit, simply running /sbin/grub causes it to segfault:
[ 3145.999766] grub[6706] general protection ip:805c481 sp:ff95629c error:0 in
grub[8048000+8c000]
i've excluded this commit for now.
Ingo
Quoted 25 lines · Ingo Molnar
Quoted 12 lines · tip-bot for Brian Gerst
Commit-ID: f19a25c872b20ae4357f72687cf3e7b0da220ee2
Gitweb: http://git.kernel.org/tip/f19a25c872b20ae4357f72687cf3e7b0da220ee2
Author: Brian Gerst <[email protected]>
AuthorDate: Mon, 25 Jan 2010 10:47:33 -0500
Committer: H. Peter Anvin <[email protected]>
CommitDate: Tue, 26 Jan 2010 23:38:14 -0800x86-64: Use normal ptregs stub for execve
Execve historically passed regs by value, so it had a seperate stub. This is no longer true, so change it to use a normal PTREGSCALL stub.
Quoted 6 lines
Signed-off-by Brian Gerst <[email protected]>LKML-Reference: <[email protected]>
Signed-off-by H. Peter Anvin <[email protected]>---
arch/x86/kernel/entry_64.S | 17 +----------------1 files changed, 1 insertions(+), 16 deletions(-)FYI, -tip testing found that this commit breaks the grub binary on 64-bit, simply running
/sbin/grubcauses it to segfault:
Quoted 8 lines
[ 3145.999766] grub[6706] general protection ip:805c481 sp:ff95629c error:0 ingrub[8048000+8c000]
i've excluded this commit for now.
Ingo
I see what is going on. Grub is a 32-bit statically linked executable even on a 64-bit distro. The old execve stub forced return to userspace via iret, but PTREGSCALL apparently doesn't. This means that the 32-bit %cs isn't getting set. Drop this patch for now.
--
Brian Gerst
H. Peter Anvin
reviewerQuoted 6 lines · Brian Gerst
I see what is going on. Grub is a 32-bit statically linked executable even on a 64-bit distro. The old execve stub forced return to userspace via iret, but PTREGSCALL apparently doesn't. This means that the 32-bit %cs isn't getting set. Drop this patch for now.
OK, I presume that breaks execing any 32-bit app, not just statically linked (eww...)
Yet one more case of Grub making me shudder, though :-/
-hpa
Signature · 2 lines
H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.