linux-kernel - Re: [PATCH v2 9/9] objtool: Abstract unwind hint reading

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Date:   Thu, 30 Jul 2020 10:03:41 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Julien Thierry <jthierry@...hat.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, mbenes@...e.cz,
        raphael.gault@....com, benh@...nel.crashing.org
Subject: Re: [PATCH v2 9/9] objtool: Abstract unwind hint reading

On Thu, Jul 30, 2020 at 10:46:52AM +0100, Julien Thierry wrote:
> The type of unwind hints and the semantics associated with them depend
> on the architecture. Let arch specific code convert unwind hints into
> objtool stack state descriptions.
> 
> Signed-off-by: Julien Thierry <jthierry@...hat.com>
> ---
>  tools/objtool/arch.h            |  5 +--
>  tools/objtool/arch/x86/decode.c | 54 ++++++++++++++++++++++++++++++
>  tools/objtool/cfi.h             |  3 +-
>  tools/objtool/check.c           | 58 +++++----------------------------
>  tools/objtool/orc_gen.c         |  4 ++-
>  5 files changed, 71 insertions(+), 53 deletions(-)
> 
> diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
> index 2e2ce089b0e9..44107e9aab71 100644
> --- a/tools/objtool/arch.h
> +++ b/tools/objtool/arch.h
> @@ -7,12 +7,11 @@
>  #define _ARCH_H
>  
>  #include <stdbool.h>
> +#include <linux/frame.h>
>  #include <linux/list.h>
>  #include "objtool.h"
>  #include "cfi.h"
>  
> -#include <asm/orc_types.h>
> -
>  enum insn_type {
>  	INSN_JUMP_CONDITIONAL,
>  	INSN_JUMP_UNCONDITIONAL,
> @@ -86,4 +85,6 @@ unsigned long arch_dest_reloc_offset(int addend);
>  
>  const char *arch_nop_insn(int len);
>  
> +int arch_decode_insn_hint(struct instruction *insn, struct unwind_hint *hint);
> +
>  #endif /* _ARCH_H */
> diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
> index 1967370440b3..2099809925af 100644
> --- a/tools/objtool/arch/x86/decode.c
> +++ b/tools/objtool/arch/x86/decode.c
> @@ -6,6 +6,8 @@
>  #include <stdio.h>
>  #include <stdlib.h>
>  
> +#include <linux/frame.h>
> +
>  #define unlikely(cond) (cond)
>  #include <asm/insn.h>
>  #include "../../../arch/x86/lib/inat.c"
> @@ -15,6 +17,7 @@
>  #include "../../elf.h"
>  #include "../../arch.h"
>  #include "../../warn.h"
> +#include <asm/orc_types.h>
>  
>  static unsigned char op_to_cfi_reg[][2] = {
>  	{CFI_AX, CFI_R8},
> @@ -583,3 +586,54 @@ const char *arch_nop_insn(int len)
>  
>  	return nops[len-1];
>  }
> +
> +int arch_decode_insn_hint(struct instruction *insn, struct unwind_hint *hint)
> +{
> +	struct cfi_reg *cfa = &insn->cfi.cfa;
> +
> +	if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
> +		insn->ret_offset = hint->sp_offset;
> +		return 0;
> +	}
> +
> +	insn->hint = true;
> +
> +	switch (hint->sp_reg) {
> +	case ORC_REG_UNDEFINED:
> +		cfa->base = CFI_UNDEFINED;
> +		break;
> +	case ORC_REG_SP:
> +		cfa->base = CFI_SP;
> +		break;
> +	case ORC_REG_BP:
> +		cfa->base = CFI_BP;
> +		break;
> +	case ORC_REG_SP_INDIRECT:
> +		cfa->base = CFI_SP_INDIRECT;
> +		break;
> +	case ORC_REG_R10:
> +		cfa->base = CFI_R10;
> +		break;
> +	case ORC_REG_R13:
> +		cfa->base = CFI_R13;
> +		break;
> +	case ORC_REG_DI:
> +		cfa->base = CFI_DI;
> +		break;
> +	case ORC_REG_DX:
> +		cfa->base = CFI_DX;
> +		break;
> +	default:
> +		WARN_FUNC("unsupported unwind_hint sp base reg %d",
> +			  insn->sec, insn->offset, hint->sp_reg);
> +		return -1;
> +	}
> +
> +	cfa->offset = hint->sp_offset;
> +	insn->cfi.hint_type = hint->type;
> +	insn->cfi.end = hint->end;
> +
> +	insn->cfi.sp_only = hint->type == ORC_TYPE_REGS || hint->type == ORC_TYPE_REGS_IRET;

What does "sp" mean here in sp_only?

> +		if (arch_decode_insn_hint(insn, hint)) {
> +			WARN_FUNC("Bad unwind hint", insn->sec, insn->offset);

No need for a warning here, since the arch-specific function already
prints one.

-- 
Josh