* Borislav Petkov <b...@alien8.de> wrote:
> Anyone think this is an OK-ish idea?
>
> It saves us the global symbol but requires the two functions to remained
> glued together. :-\
>
> ---
> diff --git a/arch/x86/entry/entry_64_compat.S
> b/arch/x86/entry/entry_64_compat.S
> index e1721dafbcb1..262519da8661 100644
> --- a/arch/x86/entry/entry_64_compat.S
> +++ b/arch/x86/entry/entry_64_compat.S
> @@ -131,7 +131,6 @@ ENTRY(entry_SYSENTER_compat)
> pushq $X86_EFLAGS_FIXED
> popfq
> jmp .Lsysenter_flags_fixed
> -GLOBAL(__end_entry_SYSENTER_compat)
> ENDPROC(entry_SYSENTER_compat)
>
> /*
> @@ -180,6 +179,9 @@ ENDPROC(entry_SYSENTER_compat)
> * edi arg5
> * esp user stack
> * 0(%esp) arg6
> + *
> + * DO NOT! move this function and the above before adjusting
> + * is_sysenter_singlestep().
> */
> ENTRY(entry_SYSCALL_compat)
> /* Interrupts are off on entry. */
> diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
> index 8d3964fc5f91..afdef9f3f0f0 100644
> --- a/arch/x86/include/asm/proto.h
> +++ b/arch/x86/include/asm/proto.h
> @@ -21,7 +21,6 @@ void __end_SYSENTER_singlestep_region(void);
>
> #ifdef CONFIG_IA32_EMULATION
> void entry_SYSENTER_compat(void);
> -void __end_entry_SYSENTER_compat(void);
> void entry_SYSCALL_compat(void);
> void entry_INT80_compat(void);
> #endif
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index bf54309b85da..143902ffe9ff 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -668,7 +668,7 @@ static bool is_sysenter_singlestep(struct pt_regs *regs)
> (unsigned long)__begin_SYSENTER_singlestep_region;
> #elif defined(CONFIG_IA32_EMULATION)
> return (regs->ip - (unsigned long)entry_SYSENTER_compat) <
> - (unsigned long)__end_entry_SYSENTER_compat -
> + (unsigned long)entry_SYSCALL_compat -
> (unsigned long)entry_SYSENTER_compat;
> #else
> return false;
Hm, I'd argue that the old code is much clearer: we need both the start and the
end of a function and have the properly named symbols for that.
That entry_SYSCALL_compat() happens to start just where
__end_entry_SYSENTER_compat is an accident of placement.
Is it even true - doesn't ENTRY() imply an .align, in which case it might be
that
__end_entry_SYSENTER_compat != entry_SYSCALL_compat?
In fact that appears to be the case for my defconfig:
ffffffff81942f90 T entry_SYSENTER_compat
ffffffff81942feb T __end_entry_SYSENTER_compat
ffffffff81942ff0 T entry_SYSCALL_compat
So unless there's some disadvantage beyond having one more symbol, I'd favor
the
old approach.
Thanks,
Ingo
