[PATCH v5 06/10] x86/asm/efi: Fix asmvalidate warnings for efi_stub_64.S

[PATCH v5 06/10] x86/asm/efi: Fix asmvalidate warnings for efi_stub_64.S

[Josh Poimboeuf]

Fix the following asmvalidate warnings:

   asmvalidate: arch/x86/platform/efi/efi_stub_64.o: efi_call(): missing FP_SAVE/RESTORE macros
   asmvalidate: arch/x86/boot/compressed/efi_stub_64.o: efi_call(): missing FP_SAVE/RESTORE macros

efi_call() is a non-leaf callable function, so save/restore the frame
pointer with FP_SAVE/RESTORE.

Signed-off-by: Josh Poimboeuf <jpoimboe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
---
 arch/x86/platform/efi/efi_stub_64.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S
index 86d0f9e..0ca6bfb 100644
--- a/arch/x86/platform/efi/efi_stub_64.S
+++ b/arch/x86/platform/efi/efi_stub_64.S
@@ -11,6 +11,7 @@
 #include <asm/msr.h>
 #include <asm/processor-flags.h>
 #include <asm/page_types.h>
+#include <asm/func.h>
 
 #define SAVE_XMM			\
 	mov %rsp, %rax;			\
@@ -74,6 +75,7 @@
 	.endm
 
 ENTRY(efi_call)
+	FP_SAVE
 	SAVE_XMM
 	mov (%rsp), %rax
 	mov 8(%rax), %rax
@@ -88,6 +90,7 @@ ENTRY(efi_call)
 	RESTORE_PGT
 	addq $48, %rsp
 	RESTORE_XMM
+	FP_RESTORE
 	ret
 ENDPROC(efi_call)
 
-- 
2.1.0

Re: [PATCH v5 06/10] x86/asm/efi: Fix asmvalidate warnings for efi_stub_64.S

[Matt Fleming]

On Wed, 10 Jun, at 07:06:14AM, Josh Poimboeuf wrote:
> Fix the following asmvalidate warnings:
> 
>    asmvalidate: arch/x86/platform/efi/efi_stub_64.o: efi_call(): missing FP_SAVE/RESTORE macros
>    asmvalidate: arch/x86/boot/compressed/efi_stub_64.o: efi_call(): missing FP_SAVE/RESTORE macros
> 
> efi_call() is a non-leaf callable function, so save/restore the frame
> pointer with FP_SAVE/RESTORE.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> ---
>  arch/x86/platform/efi/efi_stub_64.S | 3 +++
>  1 file changed, 3 insertions(+)

Yeah, fair enough. Though it's worth noting that because we're calling
firmware functions, which use the Microsoft ABI, %rbp will be saved by
the callee function if used. Anyway,

Acked-by: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

And since I know Boris in particular has poked around in this area, an
ACK from him would be worth alot.

-- 
Matt Fleming, Intel Open Source Technology Center

Re: [PATCH v5 06/10] x86/asm/efi: Fix asmvalidate warnings for efi_stub_64.S

[Borislav Petkov]

On Thu, Jun 11, 2015 at 02:14:39PM +0100, Matt Fleming wrote:
> Yeah, fair enough. Though it's worth noting that because we're calling
> firmware functions, which use the Microsoft ABI, %rbp will be saved by
> the callee function if used.

Yeah, just looked at the spec.

But you know how we don't trust specs. So we get additional paranoid
security that callee won't futz with RBP because we save it before
calling. But we pay the additional penalty in the CONFIG_FRAME_POINTER
case.

Oh what the hell, the 3 additional insns shouldn't be noticeable.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--