2019-07-30 19:14:35

by Thomas Garnier

Subject: [PATCH v9 11/11] x86/alternatives: Adapt assembly for PIE support

Change the assembly options to work with pointers instead of integers.

Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range below 0xffffffff80000000.

Signed-off-by: Thomas Garnier <[email protected]>
---
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 094fbc9c0b1c..28a838106e5f 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 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 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
--
2.22.0.770.g0f2c4a37fd-goog

2019-08-12 13:58:52

by Borislav Petkov

Subject: Re: [PATCH v9 11/11] x86/alternatives: Adapt assembly for PIE support

On Tue, Jul 30, 2019 at 12:12:55PM -0700, Thomas Garnier wrote:
> Change the assembly options to work with pointers instead of integers.

This commit message is too vague. A before/after example would make it a
lot more clear why the change is needed.

Thx.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

2019-10-29 21:34:48

by Thomas Garnier

Subject: Re: [PATCH v9 11/11] x86/alternatives: Adapt assembly for PIE support

On Mon, Aug 12, 2019 at 6:56 AM Borislav Petkov <[email protected]> wrote:
>
> On Tue, Jul 30, 2019 at 12:12:55PM -0700, Thomas Garnier wrote:
> > Change the assembly options to work with pointers instead of integers.
>
> This commit message is too vague. A before/after example would make it a
> lot more clear why the change is needed.

Sorry for the late reply, busy couple months.

I will try to do my best to explain it better in next iteration.

>
> Thx.
>
> --
> Regards/Gruss,
> Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.