Commit-ID: 4d516f41704055710da872b62ddc4b6d23248984 Gitweb: http://git.kernel.org/tip/4d516f41704055710da872b62ddc4b6d23248984 Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> AuthorDate: Wed, 21 Sep 2016 16:04:01 -0500 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Thu, 20 Oct 2016 09:15:22 +0200 x86/entry/32: Fix the end of the stack for newly forked tasks Thanks to all the recent x86 entry code refactoring, most tasks' kernel stacks start at the same offset right below their saved pt_regs, regardless of which syscall was used to enter the kernel. That creates a nice convention which makes it straightforward to identify the end of the stack, which can be useful for the unwinder to verify the stack is sane. Calling schedule_tail() directly breaks that convention because its an asmlinkage function so its argument has to be pushed on the stack. Add a wrapper which creates a proper "end of stack" frame header before the call. Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Nilay Vaish <nilayvaish@xxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/ecafcd882676bf48ceaf50483782552bb98476e5.1474480779.git.jpoimboe@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/entry/entry_32.S | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 9bd0087..2225105 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -45,6 +45,7 @@ #include <asm/asm.h> #include <asm/smap.h> #include <asm/export.h> +#include <asm/frame.h> .section .entry.text, "ax" @@ -238,6 +239,23 @@ ENTRY(__switch_to_asm) END(__switch_to_asm) /* + * The unwinder expects the last frame on the stack to always be at the same + * offset from the end of the page, which allows it to validate the stack. + * Calling schedule_tail() directly would break that convention because its an + * asmlinkage function so its argument has to be pushed on the stack. This + * wrapper creates a proper "end of stack" frame header before the call. + */ +ENTRY(schedule_tail_wrapper) + FRAME_BEGIN + + pushl %eax + call schedule_tail + popl %eax + + FRAME_END + ret +ENDPROC(schedule_tail_wrapper) +/* * A newly forked process directly context switches into this address. * * eax: prev task we switched from @@ -245,9 +263,7 @@ END(__switch_to_asm) * edi: kernel thread arg */ ENTRY(ret_from_fork) - pushl %eax - call schedule_tail - popl %eax + call schedule_tail_wrapper testl %ebx, %ebx jnz 1f /* kernel threads are uncommon */ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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