diff options
| author |   Juergen Gross <jgross@suse.com> | 2021-03-11 15:23:10 +0100 |
|---|---|---|
| committer |   Borislav Petkov <bp@suse.de> | 2021-03-11 16:44:01 +0100 |
| commit | dda7bb76484978316bb412a353789ebc5901de36 (patch) | |
| tree | baace2b80cff441e8f9ba318b9367bfadaef8161 /arch/x86/include/asm/alternative.h | |
| parent | x86/paravirt: Switch time pvops functions to use static_call() (diff) | |
| download | linux-dev-dda7bb76484978316bb412a353789ebc5901de36.tar.xz linux-dev-dda7bb76484978316bb412a353789ebc5901de36.zip | |
x86/alternative: Support not-feature
Add support for alternative patching for the case a feature is not
present on the current CPU. For users of ALTERNATIVE() and friends, an
inverted feature is specified by applying the ALT_NOT() macro to it,
e.g.:
ALTERNATIVE(old, new, ALT_NOT(feature));
Committer note:
The decision to encode the NOT-bit in the feature bit itself is because
a future change which would make objtool generate such alternative
calls, would keep the code in objtool itself fairly simple.
Also, this allows for the alternative macros to support the NOT feature
without having to change them.
Finally, the u16 cpuid member encoding the X86_FEATURE_ flags is not an
ABI so if more bits are needed, cpuid itself can be enlarged or a flags
field can be added to struct alt_instr after having considered the size
growth in either cases.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210311142319.4723-6-jgross@suse.com
Diffstat (limited to 'arch/x86/include/asm/alternative.h')
| -rw-r--r-- | arch/x86/include/asm/alternative.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 53f295f41c34..649e56f70889 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -6,6 +6,9 @@ #include <linux/stringify.h> #include <asm/asm.h> +#define ALTINSTR_FLAG_INV (1 << 15) +#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV) + #ifndef __ASSEMBLY__ #include <linux/stddef.h> |