The following commit has been merged into the x86/paravirt branch of tip: Commit-ID: 2e1f8e55f9e054b4a49ffc06c7e33b5d4725f05e Gitweb: https://git.kernel.org/tip/2e1f8e55f9e054b4a49ffc06c7e33b5d4725f05e Author: Jan Beulich <jbeulich@xxxxxxxx> AuthorDate: Thu, 30 Sep 2021 14:40:38 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Mon, 24 Jan 2022 20:21:19 +01:00 x86/paravirt: Use %rip-relative addressing in hook calls While using a plain (constant) address works, its use needlessly invokes a SIB addressing mode, making every call site one byte larger than necessary: ff 14 25 98 89 42 82 call *0xffffffff82428998 Instead of using an "i" constraint with address-of operator and a 'c' operand modifier, simply use an ordinary "m" constraint, which the 64-bit compiler will translate to %rip-relative addressing: ff 15 62 fb d2 00 call *0xd2fb62(%rip) # ffffffff82428998 <pv_ops+0x18> This way the compiler is also told the truth about operand usage - the memory location gets actually read, after all. 32-bit code generation is unaffected by the change. [ bp: Remove "we", add examples. ] Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Link: https://lore.kernel.org/r/b8192e8a-13ef-6ac6-6364-8ba58992cd1d@xxxxxxxx --- arch/x86/include/asm/paravirt_types.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index a69012e..e159146 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -279,7 +279,7 @@ extern void (*paravirt_iret)(void); #define paravirt_type(op) \ [paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \ - [paravirt_opptr] "i" (&(pv_ops.op)) + [paravirt_opptr] "m" (pv_ops.op) #define paravirt_clobber(clobber) \ [paravirt_clobber] "i" (clobber) @@ -316,7 +316,7 @@ int paravirt_disable_iospace(void); */ #define PARAVIRT_CALL \ ANNOTATE_RETPOLINE_SAFE \ - "call *%c[paravirt_opptr];" + "call *%[paravirt_opptr];" /* * These macros are intended to wrap calls through one of the paravirt
|