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| author |   Jan Beulich <jbeulich@suse.com> | 2021-09-30 14:40:38 +0200 |
|---|---|---|
| committer |   Borislav Petkov <bp@suse.de> | 2022-01-24 20:21:19 +0100 |
| commit | 2e1f8e55f9e054b4a49ffc06c7e33b5d4725f05e (patch) | |
| tree | 68a4eb3778d6b1a4ae74b300c419ece6effe3018 | |
| parent | Linux 5.17-rc1 (diff) | |
| download | linux-dev-2e1f8e55f9e054b4a49ffc06c7e33b5d4725f05e.tar.xz linux-dev-2e1f8e55f9e054b4a49ffc06c7e33b5d4725f05e.zip | |
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@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/b8192e8a-13ef-6ac6-6364-8ba58992cd1d@suse.com
| -rw-r--r-- | arch/x86/include/asm/paravirt_types.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index a69012e1903f..e1591467668e 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 |