linux-kernel - Re: [PATCH 25/33] x86/kvm: Set ELF function type for fastop functions

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Date:	Fri, 22 Jan 2016 11:05:22 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Gleb Natapov <gleb@...nel.org>, kvm@...r.kernel.org
Subject: Re: [PATCH 25/33] x86/kvm: Set ELF function type for fastop functions



On 21/01/2016 23:49, Josh Poimboeuf wrote:
> The callable functions created with the FOP* and FASTOP* macros are
> missing ELF function annotations, which confuses tools like stacktool.
> Properly annotate them.
> 
> This adds some additional labels to the assembly, but the generated
> binary code is unchanged (with the exception of instructions which have
> embedded references to __LINE__).
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Cc: Gleb Natapov <gleb@...nel.org>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: kvm@...r.kernel.org
> ---
>  arch/x86/kvm/emulate.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 1505587..aa4d726 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -309,23 +309,29 @@ static void invalidate_registers(struct x86_emulate_ctxt *ctxt)
>  
>  static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *));
>  
> -#define FOP_ALIGN ".align " __stringify(FASTOP_SIZE) " \n\t"
> +#define FOP_FUNC(name) \
> +	".align " __stringify(FASTOP_SIZE) " \n\t" \
> +	".type " name ", @function \n\t" \
> +	name ":\n\t"
> +
>  #define FOP_RET   "ret \n\t"
>  
>  #define FOP_START(op) \
>  	extern void em_##op(struct fastop *fake); \
>  	asm(".pushsection .text, \"ax\" \n\t" \
>  	    ".global em_" #op " \n\t" \
> -            FOP_ALIGN \
> -	    "em_" #op ": \n\t"
> +	    FOP_FUNC("em_" #op)
>  
>  #define FOP_END \
>  	    ".popsection")
>  
> -#define FOPNOP() FOP_ALIGN FOP_RET
> +#define FOPNOP() \
> +	FOP_FUNC(__stringify(__UNIQUE_ID(nop))) \
> +	FOP_RET
>  
>  #define FOP1E(op,  dst) \
> -	FOP_ALIGN "10: " #op " %" #dst " \n\t" FOP_RET
> +	FOP_FUNC(#op "_" #dst) \
> +	"10: " #op " %" #dst " \n\t" FOP_RET
>  
>  #define FOP1EEX(op,  dst) \
>  	FOP1E(op, dst) _ASM_EXTABLE(10b, kvm_fastop_exception)
> @@ -357,7 +363,8 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *));
>  	FOP_END
>  
>  #define FOP2E(op,  dst, src)	   \
> -	FOP_ALIGN #op " %" #src ", %" #dst " \n\t" FOP_RET
> +	FOP_FUNC(#op "_" #dst "_" #src) \
> +	#op " %" #src ", %" #dst " \n\t" FOP_RET
>  
>  #define FASTOP2(op) \
>  	FOP_START(op) \
> @@ -395,7 +402,8 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *));
>  	FOP_END
>  
>  #define FOP3E(op,  dst, src, src2) \
> -	FOP_ALIGN #op " %" #src2 ", %" #src ", %" #dst " \n\t" FOP_RET
> +	FOP_FUNC(#op "_" #dst "_" #src "_" #src2) \
> +	#op " %" #src2 ", %" #src ", %" #dst " \n\t" FOP_RET
>  
>  /* 3-operand, word-only, src2=cl */
>  #define FASTOP3WCL(op) \
> @@ -407,7 +415,12 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *));
>  	FOP_END
>  
>  /* Special case for SETcc - 1 instruction per cc */
> -#define FOP_SETCC(op) ".align 4; " #op " %al; ret \n\t"
> +#define FOP_SETCC(op) \
> +	".align 4 \n\t" \
> +	".type " #op ", @function \n\t" \
> +	#op ": \n\t" \
> +	#op " %al \n\t" \
> +	FOP_RET
>  
>  asm(".global kvm_fastop_exception \n"
>      "kvm_fastop_exception: xor %esi, %esi; ret");
> 

Acked-by: Paolo Bonzini <pbonzini@...hat.com>