Messages in this thread | | | Date | Mon, 20 Nov 2023 18:15:07 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/mm/encrypt: Use %a asm operand modifier to obtain %rip-relative address |
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On Mon, Nov 20, 2023 at 04:33:50PM +0100, Uros Bizjak wrote: > The "a" asm operand modifier substitutes a memory reference, with the > actual operand treated as address. For x86_64, when a symbol is > provided, the "a" modifier emits "sym(%rip)" instead of "sym". > > Clang allows only "i" and "r" operand constraints with an "a" modifier, > so the patch normalizes the modifier/constraint pair to "a"/"i"
s/the patch normalizes/normalize/
> which is consistent between both compilers. > > No functional change intended. > > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Borislav Petkov <bp@alien8.de> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Signed-off-by: Uros Bizjak <ubizjak@gmail.com> > --- > arch/x86/mm/mem_encrypt_identity.c | 16 ++++------------ > 1 file changed, 4 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c > index d73aeb16417f..6a351fdd1b39 100644 > --- a/arch/x86/mm/mem_encrypt_identity.c > +++ b/arch/x86/mm/mem_encrypt_identity.c > @@ -346,9 +346,7 @@ void __init sme_encrypt_kernel(struct boot_params *bp) > * We're running identity mapped, so we must obtain the address to the > * SME encryption workarea using rip-relative addressing. > */ > - asm ("lea sme_workarea(%%rip), %0" > - : "=r" (workarea_start) > - : "p" (sme_workarea)); > + asm ("lea %a1, %0" : "=r" (workarea_start) : "i" (sme_workarea));
Yeah, I saw that particular subthread today.
Are you sure this "a" modifier DTRT with all gcc version we support?
I.e., from 5.1 onwards...
Just making sure.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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