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From: Mark Rutland <mark.rutland@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com,
	jpoimboe@redhat.com, andrew.cooper3@citrix.com,
	linux-kernel@vger.kernel.org, ndesaulniers@google.com,
	keescook@chromium.org, samitolvanen@google.com
Subject: Re: [RFC][PATCH 1/6] x86: Annotate _THIS_IP_
Date: Tue, 23 Nov 2021 13:53:49 +0000	[thread overview]
Message-ID: <20211123135348.GE37253@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20211122170805.025419814@infradead.org>

On Mon, Nov 22, 2021 at 06:03:02PM +0100, Peter Zijlstra wrote:
> In order to find _THIS_IP_ code references in objtool, annotate them.

Just to check my understanding, IIUC this is because in later patches
you'll look at text relocations to spot missing ENDBRs, and when doing
so you need to filter out _THIS_IP_ instances, since those don't need an
ENDBR. Is that right?

Just checking I haven't missed some other concern that might apply to
arm64's BTI (Branch Target Identifier), which are analagous to ENDBR.

Thanks,
Mark.

> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  arch/x86/include/asm/linkage.h      |   11 +++++++++++
>  include/linux/instruction_pointer.h |    5 +++++
>  2 files changed, 16 insertions(+)
> 
> --- a/arch/x86/include/asm/linkage.h
> +++ b/arch/x86/include/asm/linkage.h
> @@ -3,10 +3,21 @@
>  #define _ASM_X86_LINKAGE_H
>  
>  #include <linux/stringify.h>
> +#include <asm/asm.h>
>  
>  #undef notrace
>  #define notrace __attribute__((no_instrument_function))
>  
> +#define _THIS_IP_						\
> +	({	__label__ __here;				\
> +		__here:						\
> +		asm_volatile_goto (				\
> +		    ".pushsection .discard.this_ip\n\t"		\
> +		    _ASM_PTR " %l[__here]\n\t"			\
> +		    ".popsection\n\t"				\
> +		    : : : : __here);				\
> +		(unsigned long)&&__here; })
> +
>  #ifdef CONFIG_X86_32
>  #define asmlinkage CPP_ASMLINKAGE __attribute__((regparm(0)))
>  #endif /* CONFIG_X86_32 */
> --- a/include/linux/instruction_pointer.h
> +++ b/include/linux/instruction_pointer.h
> @@ -2,7 +2,12 @@
>  #ifndef _LINUX_INSTRUCTION_POINTER_H
>  #define _LINUX_INSTRUCTION_POINTER_H
>  
> +#include <asm/linkage.h>
> +
>  #define _RET_IP_		(unsigned long)__builtin_return_address(0)
> +
> +#ifndef _THIS_IP_
>  #define _THIS_IP_  ({ __label__ __here; __here: (unsigned long)&&__here; })
> +#endif
>  
>  #endif /* _LINUX_INSTRUCTION_POINTER_H */
> 
> 

  reply	other threads:[~2021-11-23 13:53 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-22 17:03 [RFC][PATCH 0/6] x86: Kernel IBT beginnings Peter Zijlstra
2021-11-22 17:03 ` [RFC][PATCH 1/6] x86: Annotate _THIS_IP_ Peter Zijlstra
2021-11-23 13:53   ` Mark Rutland [this message]
2021-11-23 14:14     ` Peter Zijlstra
2021-11-24 18:18       ` Josh Poimboeuf
2021-11-22 17:03 ` [RFC][PATCH 2/6] x86: Base IBT bits Peter Zijlstra
2022-02-08 23:32   ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 3/6] x86: Add ENDBR to IRET-to-Self Peter Zijlstra
2021-11-22 18:09   ` Peter Zijlstra
2022-02-08 23:33     ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 4/6] objtool: Read the _THIS_IP_ hints Peter Zijlstra
2021-11-22 17:03 ` [RFC][PATCH 5/6] x86: Sprinkle ENDBR dust Peter Zijlstra
2021-11-23 14:00   ` Mark Rutland
2021-11-23 14:21     ` Peter Zijlstra
2022-02-08 23:38     ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 6/6] objtool: Add IBT validation / fixups Peter Zijlstra
2021-11-24 19:30   ` Josh Poimboeuf
2022-02-08 23:43     ` Kees Cook
2022-02-09  5:09       ` Josh Poimboeuf
2022-02-09 11:41       ` Peter Zijlstra
2022-02-09 11:45         ` Peter Zijlstra
2021-12-24  2:05   ` joao
2022-02-08 23:42     ` Kees Cook
2022-02-09  2:21       ` Joao Moreira
2022-02-09  4:05         ` Kees Cook
2022-02-09  5:18           ` Joao Moreira
2022-02-11 13:38             ` Peter Zijlstra
2022-02-14 21:38               ` Sami Tolvanen
2022-02-14 22:25                 ` Peter Zijlstra
2022-02-15 16:56                   ` Sami Tolvanen
2022-02-15 20:03                     ` Kees Cook
2022-02-15 21:05                       ` Peter Zijlstra
2022-02-15 23:05                         ` Kees Cook
2022-02-15 23:38                           ` Joao Moreira
2022-02-16 12:24                         ` Peter Zijlstra
2022-02-15 20:53                     ` Peter Zijlstra
2022-02-15 22:45               ` Joao Moreira
2022-02-16  0:57               ` Andrew Cooper
2022-03-02  3:06               ` Peter Collingbourne
2022-03-02  3:32                 ` Joao Moreira
2022-06-08 17:53                 ` Fāng-ruì Sòng
2022-06-09  0:05                   ` Sami Tolvanen
2021-11-23  7:58 ` [RFC][PATCH 0/6] x86: Kernel IBT beginnings Christoph Hellwig
2021-11-23  9:02   ` Peter Zijlstra
2022-02-08 23:48 ` Kees Cook
2022-02-09  0:09 ` Nick Desaulniers

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