From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
In filter_cpuid_features(), x86_cap_flags[] is read, but it's not verified
whether the string is non-zero which could lead to unwanted output.
In two more places there are open coded paths that try to retrieve a
feature string, and if there isn't one, the feature word and bit are
returned instead.
Add a common helper to fix filter_cpuid_features() as well as clean up
the open coded cases.
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
---
Changelog v10:
- Reword the patch message a bit.
- Move x86_cap_name() declaration and X86_CAP_BUF_SIZE define to
asm/cpufeature.h.
- Don't include asm/cpu.h in cpuid-deps.c
- Extend the comment above x86_cap_name to include information on buffer
size that needs to be prepared before calling the function.
- Remove the likely(), unlikely() calls since this is not a hot path.
Changelog v9:
- 16 -> X86_CAP_BUF_SIZE.
- Add comment to the x86_cap_name().
Changelog v8:
- Move x86_cap_name() declaration from linux/cpu.h to the arch/cpu.h.
Include arch/cpu.h in the cpuid-deps.c file instead of linux/cpu.h.
Changelog v7:
- sizeof(buf) -> 16
- Rebase onto 7.01-rc1.
Changelog v6:
- Remove parts of the patch message that are redundant and just copy
what's visible in the diff.
- Redo the helper to use an external char buffer instead of a local
static string.
arch/x86/include/asm/cpufeature.h | 4 ++++
arch/x86/kernel/cpu/common.c | 32 ++++++++++++++++++++++++++-----
arch/x86/kernel/cpu/cpuid-deps.c | 21 +++-----------------
3 files changed, 34 insertions(+), 23 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 3ddc1d33399b..dc1cd44ddd63 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -138,5 +138,9 @@ static __always_inline bool _static_cpu_has(u16 bit)
#define CPU_FEATURE_TYPEVAL boot_cpu_data.x86_vendor, boot_cpu_data.x86, \
boot_cpu_data.x86_model
+#define X86_CAP_BUF_SIZE 16
+
+const char *x86_cap_name(unsigned int bit, char *buf);
+
#endif /* defined(__KERNEL__) && !defined(__ASSEMBLER__) */
#endif /* _ASM_X86_CPUFEATURE_H */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 76339e988304..0e318f3d56cb 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -678,6 +678,7 @@ cpuid_dependent_features[] = {
static void filter_cpuid_features(struct cpuinfo_x86 *c, bool warn)
{
const struct cpuid_dependent_feature *df;
+ char feature_buf[X86_CAP_BUF_SIZE];
for (df = cpuid_dependent_features; df->feature; df++) {
@@ -700,7 +701,7 @@ static void filter_cpuid_features(struct cpuinfo_x86 *c, bool warn)
continue;
pr_warn("CPU: CPU feature %s disabled, no CPUID level 0x%x\n",
- x86_cap_flags[df->feature], df->level);
+ x86_cap_name(df->feature, feature_buf), df->level);
}
}
@@ -1637,6 +1638,7 @@ static inline bool parse_set_clear_cpuid(char *arg, bool set)
while (arg) {
bool found __maybe_unused = false;
+ char name_buf[X86_CAP_BUF_SIZE];
unsigned int bit;
opt = strsep(&arg, ",");
@@ -1657,10 +1659,7 @@ static inline bool parse_set_clear_cpuid(char *arg, bool set)
setup_clear_cpu_cap(bit);
}
/* empty-string, i.e., ""-defined feature flags */
- if (!x86_cap_flags[bit])
- pr_cont(" %d:%d\n", bit >> 5, bit & 31);
- else
- pr_cont(" %s\n", x86_cap_flags[bit]);
+ pr_cont(" %s\n", x86_cap_name(bit, name_buf));
taint++;
}
@@ -1983,6 +1982,29 @@ static void generic_identify(struct cpuinfo_x86 *c)
#endif
}
+/*
+ * Return the feature "name" if available, otherwise return the
+ * X86_FEATURE_* numerals to make it easier to identify the feature.
+ * Callers of this function need to pass a char * buffer of size
+ * X86_CAP_BUF_SIZE.
+ */
+const char *x86_cap_name(unsigned int bit, char *buf)
+{
+ unsigned int word = bit >> 5;
+ const char *name = NULL;
+
+ if (word < NCAPINTS)
+ name = x86_cap_flags[bit];
+ else if (word < NCAPINTS + NBUGINTS)
+ name = x86_bug_flags[bit - 32 * NCAPINTS];
+
+ if (name)
+ return name;
+
+ snprintf(buf, X86_CAP_BUF_SIZE, "%u:%u", word, bit & 31);
+ return buf;
+}
+
/*
* This does the hard work of actually picking apart the CPU stuff...
*/
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index 146f6f8b0650..5002f496d095 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -156,24 +156,9 @@ void setup_clear_cpu_cap(unsigned int feature)
do_clear_cpu_cap(NULL, feature);
}
-/*
- * Return the feature "name" if available, otherwise return
- * the X86_FEATURE_* numerals to make it easier to identify
- * the feature.
- */
-static const char *x86_feature_name(unsigned int feature, char *buf)
-{
- if (x86_cap_flags[feature])
- return x86_cap_flags[feature];
-
- snprintf(buf, 16, "%d*32+%2d", feature / 32, feature % 32);
-
- return buf;
-}
-
void check_cpufeature_deps(struct cpuinfo_x86 *c)
{
- char feature_buf[16], depends_buf[16];
+ char feature_buf[X86_CAP_BUF_SIZE], depends_buf[X86_CAP_BUF_SIZE];
const struct cpuid_dep *d;
for (d = cpuid_deps; d->feature; d++) {
@@ -185,8 +170,8 @@ void check_cpufeature_deps(struct cpuinfo_x86 *c)
*/
pr_warn_once("x86 CPU feature dependency check failure: CPU%d has '%s' enabled but '%s' disabled. Kernel might be fine, but no guarantees.\n",
smp_processor_id(),
- x86_feature_name(d->feature, feature_buf),
- x86_feature_name(d->depends, depends_buf));
+ x86_cap_name(d->feature, feature_buf),
+ x86_cap_name(d->depends, depends_buf));
}
}
}
--
2.53.0On Tue, Mar 17, 2026 at 08:00:16PM +0000, Maciej Wieczor-Retman wrote: > From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> > > In filter_cpuid_features(), x86_cap_flags[] is read, but it's not verified > whether the string is non-zero which could lead to unwanted output. > > In two more places there are open coded paths that try to retrieve a > feature string, and if there isn't one, the feature word and bit are > returned instead. > > Add a common helper to fix filter_cpuid_features() as well as clean up > the open coded cases. > > Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> > --- > Changelog v10: > - Reword the patch message a bit. > - Move x86_cap_name() declaration and X86_CAP_BUF_SIZE define to > asm/cpufeature.h. > - Don't include asm/cpu.h in cpuid-deps.c > - Extend the comment above x86_cap_name to include information on buffer > size that needs to be prepared before calling the function. > - Remove the likely(), unlikely() calls since this is not a hot path. > > Changelog v9: > - 16 -> X86_CAP_BUF_SIZE. > - Add comment to the x86_cap_name(). > > Changelog v8: > - Move x86_cap_name() declaration from linux/cpu.h to the arch/cpu.h. > Include arch/cpu.h in the cpuid-deps.c file instead of linux/cpu.h. > > Changelog v7: > - sizeof(buf) -> 16 > - Rebase onto 7.01-rc1. > > Changelog v6: > - Remove parts of the patch message that are redundant and just copy > what's visible in the diff. > - Redo the helper to use an external char buffer instead of a local > static string. > > arch/x86/include/asm/cpufeature.h | 4 ++++ > arch/x86/kernel/cpu/common.c | 32 ++++++++++++++++++++++++++----- > arch/x86/kernel/cpu/cpuid-deps.c | 21 +++----------------- > 3 files changed, 34 insertions(+), 23 deletions(-) > > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index 3ddc1d33399b..dc1cd44ddd63 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -138,5 +138,9 @@ static __always_inline bool _static_cpu_has(u16 bit) > #define CPU_FEATURE_TYPEVAL boot_cpu_data.x86_vendor, boot_cpu_data.x86, \ > boot_cpu_data.x86_model > > +#define X86_CAP_BUF_SIZE 16 This can get rid of the extra tab. Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
On 2026-03-18 at 16:41:58 -0700, Pawan Gupta wrote: >On Tue, Mar 17, 2026 at 08:00:16PM +0000, Maciej Wieczor-Retman wrote: >> From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> >> >> In filter_cpuid_features(), x86_cap_flags[] is read, but it's not verified >> whether the string is non-zero which could lead to unwanted output. >> >> In two more places there are open coded paths that try to retrieve a >> feature string, and if there isn't one, the feature word and bit are >> returned instead. >> >> Add a common helper to fix filter_cpuid_features() as well as clean up >> the open coded cases. >> >> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> >> --- >> Changelog v10: >> - Reword the patch message a bit. >> - Move x86_cap_name() declaration and X86_CAP_BUF_SIZE define to >> asm/cpufeature.h. >> - Don't include asm/cpu.h in cpuid-deps.c >> - Extend the comment above x86_cap_name to include information on buffer >> size that needs to be prepared before calling the function. >> - Remove the likely(), unlikely() calls since this is not a hot path. >> >> Changelog v9: >> - 16 -> X86_CAP_BUF_SIZE. >> - Add comment to the x86_cap_name(). >> >> Changelog v8: >> - Move x86_cap_name() declaration from linux/cpu.h to the arch/cpu.h. >> Include arch/cpu.h in the cpuid-deps.c file instead of linux/cpu.h. >> >> Changelog v7: >> - sizeof(buf) -> 16 >> - Rebase onto 7.01-rc1. >> >> Changelog v6: >> - Remove parts of the patch message that are redundant and just copy >> what's visible in the diff. >> - Redo the helper to use an external char buffer instead of a local >> static string. >> >> arch/x86/include/asm/cpufeature.h | 4 ++++ >> arch/x86/kernel/cpu/common.c | 32 ++++++++++++++++++++++++++----- >> arch/x86/kernel/cpu/cpuid-deps.c | 21 +++----------------- >> 3 files changed, 34 insertions(+), 23 deletions(-) >> >> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h >> index 3ddc1d33399b..dc1cd44ddd63 100644 >> --- a/arch/x86/include/asm/cpufeature.h >> +++ b/arch/x86/include/asm/cpufeature.h >> @@ -138,5 +138,9 @@ static __always_inline bool _static_cpu_has(u16 bit) >> #define CPU_FEATURE_TYPEVAL boot_cpu_data.x86_vendor, boot_cpu_data.x86, \ >> boot_cpu_data.x86_model >> >> +#define X86_CAP_BUF_SIZE 16 > >This can get rid of the extra tab. > >Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Thanks, I'll delete that extra tab. -- Kind regards Maciej Wieczór-Retman
On 3/17/2026 1:00 PM, Maciej Wieczor-Retman wrote: > From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> > > In filter_cpuid_features(), x86_cap_flags[] is read, but it's not verified > whether the string is non-zero which could lead to unwanted output. > > In two more places there are open coded paths that try to retrieve a > feature string, and if there isn't one, the feature word and bit are > returned instead. > > Add a common helper to fix filter_cpuid_features() as well as clean up > the open coded cases. > > Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com> > --- Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
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