linux-kernel - Re: [PATCH v7 3/6] x86/asm: Simplify VDSO DWARF generation

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Message-ID: <b8d73b0e-c007-4556-960a-96ee3d74a9f5@zytor.com>
Date: Tue, 3 Feb 2026 16:44:02 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Jens Remus <jremus@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org,
        x86@...nel.org, linux-mm@...ck.org,
        Steven Rostedt <rostedt@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrii Nakryiko <andrii@...nel.org>,
        Indu Bhagat <indu.bhagat@...cle.com>,
        "Jose E. Marchesi" <jemarch@....org>,
        Beau Belgrave <beaub@...ux.microsoft.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Florian Weimer <fweimer@...hat.com>, Kees Cook <kees@...nel.org>,
        "Carlos O'Donell" <codonell@...hat.com>, Sam James <sam@...too.org>,
        Dylan Hatch <dylanbhatch@...gle.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Michal Hocko
 <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>
Subject: Re: [PATCH v7 3/6] x86/asm: Simplify VDSO DWARF generation

On 2026-02-03 09:19, Jens Remus wrote:
> From: Josh Poimboeuf <jpoimboe@...nel.org>
> 
> Add CFI_STARTPROC and CFI_ENDPROC annotations to the SYM_FUNC_* macros
> so the VDSO asm functions don't need to add them manually.  Note this
> only affects VDSO, the CFI_* macros are empty for the kernel proper.
> 
> [ Jens Remus: Reword commit subject and message as suggested by Josh. ]
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> Signed-off-by: Jens Remus <jremus@...ux.ibm.com>
> ---
>  arch/x86/entry/vdso/common/vdso-layout.lds.S  |  2 +-
>  .../x86/entry/vdso/vdso64/vgetrandom-chacha.S |  2 --
>  arch/x86/entry/vdso/vdso64/vsgx.S             |  4 ---
>  arch/x86/include/asm/linkage.h                | 33 +++++++++++++++----
>  arch/x86/include/asm/vdso.h                   |  1 -
>  5 files changed, 28 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/entry/vdso/common/vdso-layout.lds.S b/arch/x86/entry/vdso/common/vdso-layout.lds.S
> index a1e30be3e83d..856b8b9d278c 100644
> --- a/arch/x86/entry/vdso/common/vdso-layout.lds.S
> +++ b/arch/x86/entry/vdso/common/vdso-layout.lds.S
> @@ -1,5 +1,5 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
> -#include <asm/vdso.h>
> +#include <asm/page_types.h>
>  #include <asm/vdso/vsyscall.h>
>  #include <vdso/datapage.h>
>  
> diff --git a/arch/x86/entry/vdso/vdso64/vgetrandom-chacha.S b/arch/x86/entry/vdso/vdso64/vgetrandom-chacha.S
> index cc82da9216fb..a33212594731 100644
> --- a/arch/x86/entry/vdso/vdso64/vgetrandom-chacha.S
> +++ b/arch/x86/entry/vdso/vdso64/vgetrandom-chacha.S
> @@ -22,7 +22,6 @@ CONSTANTS:	.octa 0x6b20657479622d323320646e61707865
>   *	rcx: number of 64-byte blocks to write to output
>   */
>  SYM_FUNC_START(__arch_chacha20_blocks_nostack)
> -	CFI_STARTPROC
>  .set	output,		%rdi
>  .set	key,		%rsi
>  .set	counter,	%rdx
> @@ -175,5 +174,4 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
>  	pxor		temp,temp
>  
>  	ret
> -	CFI_ENDPROC
>  SYM_FUNC_END(__arch_chacha20_blocks_nostack)
> diff --git a/arch/x86/entry/vdso/vdso64/vsgx.S b/arch/x86/entry/vdso/vdso64/vsgx.S
> index 37a3d4c02366..c0342238c976 100644
> --- a/arch/x86/entry/vdso/vdso64/vsgx.S
> +++ b/arch/x86/entry/vdso/vdso64/vsgx.S
> @@ -24,8 +24,6 @@
>  .section .text, "ax"
>  
>  SYM_FUNC_START(__vdso_sgx_enter_enclave)
> -	/* Prolog */
> -	.cfi_startproc
>  	push	%rbp
>  	.cfi_adjust_cfa_offset	8
>  	.cfi_rel_offset		%rbp, 0
> @@ -143,8 +141,6 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
>  	jle	.Lout
>  	jmp	.Lenter_enclave
>  
> -	.cfi_endproc
> -
>  _ASM_VDSO_EXTABLE_HANDLE(.Lenclu_eenter_eresume, .Lhandle_exception)
>  
>  SYM_FUNC_END(__vdso_sgx_enter_enclave)
> diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
> index 9d38ae744a2e..9d7f90c57451 100644
> --- a/arch/x86/include/asm/linkage.h
> +++ b/arch/x86/include/asm/linkage.h
> @@ -40,6 +40,10 @@
>  
>  #ifdef __ASSEMBLER__
>  
> +#ifndef LINKER_SCRIPT
> +#include <asm/dwarf2.h>
> +#endif
> +
>  #if defined(CONFIG_MITIGATION_RETHUNK) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
>  #define RET	jmp __x86_return_thunk
>  #else /* CONFIG_MITIGATION_RETPOLINE */
> @@ -112,34 +116,51 @@
>  # define SYM_FUNC_ALIAS_MEMFUNC	SYM_FUNC_ALIAS
>  #endif
>  
> +#define __SYM_FUNC_START				\
> +	CFI_STARTPROC ASM_NL
> +
> +#define __SYM_FUNC_END					\
> +	CFI_ENDPROC ASM_NL
> +
>  /* SYM_TYPED_FUNC_START -- use for indirectly called globals, w/ CFI type */
>  #define SYM_TYPED_FUNC_START(name)				\
>  	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
> +	__SYM_FUNC_START					\
>  	ENDBR
>  
>  /* SYM_FUNC_START -- use for global functions */
>  #define SYM_FUNC_START(name)				\
> -	SYM_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)
> +	SYM_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
> +	__SYM_FUNC_START
>  
>  /* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
>  #define SYM_FUNC_START_NOALIGN(name)			\
> -	SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
> +	SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)	\
> +	__SYM_FUNC_START
>  
>  /* SYM_FUNC_START_LOCAL -- use for local functions */
>  #define SYM_FUNC_START_LOCAL(name)			\
> -	SYM_START(name, SYM_L_LOCAL, SYM_F_ALIGN)
> +	SYM_START(name, SYM_L_LOCAL, SYM_F_ALIGN)	\
> +	__SYM_FUNC_START
>  
>  /* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
>  #define SYM_FUNC_START_LOCAL_NOALIGN(name)		\
> -	SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
> +	SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)	\
> +	__SYM_FUNC_START
>  
>  /* SYM_FUNC_START_WEAK -- use for weak functions */
>  #define SYM_FUNC_START_WEAK(name)			\
> -	SYM_START(name, SYM_L_WEAK, SYM_F_ALIGN)
> +	SYM_START(name, SYM_L_WEAK, SYM_F_ALIGN)	\
> +	__SYM_FUNC_START
>  
>  /* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */
>  #define SYM_FUNC_START_WEAK_NOALIGN(name)		\
> -	SYM_START(name, SYM_L_WEAK, SYM_A_NONE)
> +	SYM_START(name, SYM_L_WEAK, SYM_A_NONE)		\
> +	__SYM_FUNC_START
> +
> +#define SYM_FUNC_END(name)				\
> +	__SYM_FUNC_END					\
> +	SYM_END(name, SYM_T_FUNC)
>  
>  /*
>   * Expose 'sym' to the startup code in arch/x86/boot/startup/, by emitting an
> diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
> index e8afbe9faa5b..498ac423741c 100644
> --- a/arch/x86/include/asm/vdso.h
> +++ b/arch/x86/include/asm/vdso.h
> @@ -2,7 +2,6 @@
>  #ifndef _ASM_X86_VDSO_H
>  #define _ASM_X86_VDSO_H
>  
> -#include <asm/page_types.h>
>  #include <linux/linkage.h>
>  #include <linux/init.h>
>  

Makes sense to me.

Acked-by: H. Peter Anvin (Intel) <hpa@...or.com>