Re: [GIT PULL] EFI fix

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [GIT PULL] EFI fix
Date	2016-05-17 12:30 +0200
Message-ID	<rzKqe-3kb-9@gated-at.bofh.it> (permalink)
References	<rzs0h-8f4-1@gated-at.bofh.it> <rzwZY-3eP-9@gated-at.bofh.it> <rzJaT-2C9-15@gated-at.bofh.it> <rzJNv-2Rf-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

* Matt Fleming <matt@codeblueprint.co.uk> wrote:

> On Tue, 17 May, at 10:04:34AM, Matt Fleming wrote:
> > 
> > Now I'm wondering whether other users of FRAME_BEGIN/FRAME_END make
> > this same mistake. Coccinelle might be able to detect it perhaps.
> 
> A quick bit of sed turned up the code in arch/x86/entry/entry_64.S,
> which looks to suffer from the same bug,

That would be arch/x86/entry/thunk_64.S, but yeah, good find!

>         /* rdi: arg1 ... normal C conventions. rax is saved/restored. */
>         .macro THUNK name, func, put_ret_addr_in_rdi=0
>         .globl \name
>         .type \name, @function
> \name:
>         FRAME_BEGIN
> 
>         /* this one pushes 9 elems, the next one would be %rIP */
>         pushq %rdi
>         pushq %rsi
>         pushq %rdx
>         pushq %rcx
>         pushq %rax
>         pushq %r8
>         pushq %r9
>         pushq %r10
>         pushq %r11
> 
>         .if \put_ret_addr_in_rdi
>         /* 9*8(%rsp) is return addr on stack */
>         movq 9*8(%rsp), %rdi
>         .endif
> 
> With CONFIG_FRAME_POINTER=y 9*8(%rsp) is actually the value of %rbp on
> entry, not the return address.

This seems to affect:

#ifdef CONFIG_TRACE_IRQFLAGS
        THUNK trace_hardirqs_on_thunk,trace_hardirqs_on_caller,1
        THUNK trace_hardirqs_off_thunk,trace_hardirqs_off_caller,1
#endif

and with TRACE_IRQFLAGS we already in most times force frame pointers, such as 
when LOCKDEP is enabled:

  config LOCKDEP
        bool
        depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
  ...
        select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE

Also, unlike the efi_call() case, this thunk_64.S bug affects the quality of 
debug/tracing information, not runtime correctness per se.

still all that is by accident, not by design - this bug should be fixed too.

Thanks,

	Ingo

Thread

[GIT PULL] EFI fix Ingo Molnar <mingo@kernel.org> - 2016-05-16 16:50 +0200
  Re: [GIT PULL] EFI fix Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-16 22:10 +0200
    Re: [GIT PULL] EFI fix Alex Thorlton <athorlton@sgi.com> - 2016-05-16 22:30 +0200
      Re: [GIT PULL] EFI fix Alex Thorlton <athorlton@sgi.com> - 2016-05-17 00:50 +0200
    [tip:x86/urgent] x86/efi: Fix 7-parameter efi_call()s tip-bot for Linus Torvalds <tipbot@zytor.com> - 2016-05-17 08:40 +0200
    Re: [GIT PULL] EFI fix Matt Fleming <matt@codeblueprint.co.uk> - 2016-05-17 11:10 +0200
      Re: [GIT PULL] EFI fix Matt Fleming <matt@codeblueprint.co.uk> - 2016-05-17 11:50 +0200
        Re: [GIT PULL] EFI fix Ingo Molnar <mingo@kernel.org> - 2016-05-17 12:30 +0200
          [PATCH] x86/asm/entry: fix stack return address retrieval in thunk Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-17 16:50 +0200
            Re: [PATCH] x86/asm/entry: fix stack return address retrieval in thunk Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-17 18:40 +0200
              Re: [PATCH] x86/asm/entry: fix stack return address retrieval in  thunk Steven Rostedt <rostedt@goodmis.org> - 2016-05-17 19:00 +0200
                Re: [PATCH] x86/asm/entry: fix stack return address retrieval in thunk Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-17 19:30 +0200
                Re: [PATCH] x86/asm/entry: fix stack return address retrieval in  thunk Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-17 19:30 +0200
              [PATCH v2] x86/asm/entry: fix stack return address retrieval in thunk Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-17 20:10 +0200
                Re: [PATCH v2] x86/asm/entry: fix stack return address retrieval in thunk Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-17 20:40 +0200
                [tip:x86/urgent] x86/entry/64: Fix stack return address retrieval  in thunk tip-bot for Josh Poimboeuf <tipbot@zytor.com> - 2016-05-19 11:20 +0200
    Re: [GIT PULL] EFI fix Matt Fleming <matt@codeblueprint.co.uk> - 2016-05-23 14:10 +0200
      Re: [GIT PULL] EFI fix Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-23 14:40 +0200
        Re: [GIT PULL] EFI fix Ingo Molnar <mingo@kernel.org> - 2016-05-24 11:10 +0200

csiph-web