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Date: Mon, 2 Mar 2020 20:59:59 -0800
From: Kees Cook <keescook@...omium.org>
To: Thomas Garnier <thgarnie@...omium.org>
Cc: kernel-hardening@...ts.openwall.com, kristen@...ux.intel.com,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 11/11] x86/alternatives: Adapt assembly for PIE
support
On Thu, Feb 27, 2020 at 04:00:56PM -0800, Thomas Garnier wrote:
> Change the assembly options to work with pointers instead of integers.
> The generated code is the same PIE just ensures input is a pointer.
>
> Signed-off-by: Thomas Garnier <thgarnie@...omium.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
-Kees
> ---
> arch/x86/include/asm/alternative.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index 13adca37c99a..43a148042656 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -243,7 +243,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
> /* Like alternative_io, but for replacing a direct call with another one. */
> #define alternative_call(oldfunc, newfunc, feature, output, input...) \
> asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
> - : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
> + : output : [old] "X" (oldfunc), [new] "X" (newfunc), ## input)
>
> /*
> * Like alternative_call, but there are two features and respective functions.
> @@ -256,8 +256,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
> asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
> "call %P[new2]", feature2) \
> : output, ASM_CALL_CONSTRAINT \
> - : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
> - [new2] "i" (newfunc2), ## input)
> + : [old] "X" (oldfunc), [new1] "X" (newfunc1), \
> + [new2] "X" (newfunc2), ## input)
>
> /*
> * use this macro(s) if you need more than one output parameter
> --
> 2.25.1.481.gfbce0eb801-goog
>
--
Kees Cook
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