Asm & local labels for functions [was: [PATCH v8 05/28] x86/asm: annotate local pseudo-functions]

[Jiri Slaby]

On 15. 08. 19, 18:07, Borislav Petkov wrote:
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -283,7 +283,7 @@ ENTRY(early_idt_handler_array)
>  		UNWIND_HINT_IRET_REGS offset=8
>  	.endif
>  	pushq $i		# 72(%rsp) Vector number
> -	jmp early_idt_handler_common
> +	jmp .Learly_idt_handler_common
>  	UNWIND_HINT_IRET_REGS
>  	i = i + 1
>  	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
> @@ -291,7 +291,7 @@ ENTRY(early_idt_handler_array)
>  	UNWIND_HINT_IRET_REGS offset=16
>  END(early_idt_handler_array)
>  
> -SYM_CODE_START_LOCAL(early_idt_handler_common)
> +SYM_CODE_START_LOCAL(.Learly_idt_handler_common)
>  	/*
>  	 * The stack is the hardware frame, an error code or zero, and the
>  	 * vector number.
> @@ -333,7 +333,7 @@ SYM_CODE_START_LOCAL(early_idt_handler_common)
>  20:
>  	decl early_recursion_flag(%rip)
>  	jmp restore_regs_and_return_to_kernel
> -SYM_CODE_END(early_idt_handler_common)
> +SYM_CODE_END(.Learly_idt_handler_common)

...

> All except this one can be local labels and be removed from vmlinux'
> symtable:
> 
> $ readelf -a vmlinux | grep -E "(bad_(gs|(get|put)_user)|bogus_64_magic|early_idt_handler_common|verify_cpu)"
>     45: ffffffff810000e0   241 FUNC    LOCAL  DEFAULT    1 verify_cpu
> $

Thanks for all the review hints.

Let's start with this one: do you really want me to get rid of (local)
symbols like this? It would make backtraces completely misleading as the
unwinder would put a name of the previous function (or some garbage,
depending on unwinder) into the backtrace...

thanks,
-- 
js
suse labs