[PATCH 4.19 62/79] tools/power x86_energy_perf_policy: Fix "uninitialized variable" warnings at -O2

Greg Kroah-Hartman
2019-09-19T22:14:26Z

From: Ben Hutchings <ben@decadent.org.uk>

[ Upstream commit adb8049097a9ec4acd09fbd3aa8636199a78df8a ]

x86_energy_perf_policy first uses __get_cpuid() to check the maximum
CPUID level and exits if it is too low. It then assumes that later
calls will succeed (which I think is architecturally guaranteed). It
also assumes that CPUID works at all (which is not guaranteed on
x86_32).

If optimisations are enabled, gcc warns about potentially
uninitialized variables. Fix this by adding an exit-on-error after
every call to __get_cpuid() instead of just checking the maximum
level.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../x86_energy_perf_policy.c | 26 +++++++++++--------
1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
index 65bbe627a425f..bbef8bcf44d6d 100644
--- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
+++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
@@ -1260,6 +1260,15 @@ void probe_dev_msr(void)
if (system("/sbin/modprobe msr > /dev/null 2>&1"))
err(-5, "no /dev/cpu/0/msr, Try \"# modprobe msr\" ");
}
+
+static void get_cpuid_or_exit(unsigned int leaf,
+ unsigned int *eax, unsigned int *ebx,
+ unsigned int *ecx, unsigned int *edx)
+{
+ if (!__get_cpuid(leaf, eax, ebx, ecx, edx))
+ errx(1, "Processor not supported\n");
+}
+
/*
* early_cpuid()
* initialize turbo_is_enabled, has_hwp, has_epb
@@ -1267,15 +1276,10 @@ void probe_dev_msr(void)
*/
void early_cpuid(void)
{
- unsigned int eax, ebx, ecx, edx, max_level;
+ unsigned int eax, ebx, ecx, edx;
unsigned int fms, family, model;

- __get_cpuid(0, &max_level, &ebx, &ecx, &edx);
-
- if (max_level < 6)
- errx(1, "Processor not supported\n");
-
- __get_cpuid(1, &fms, &ebx, &ecx, &edx);
+ get_cpuid_or_exit(1, &fms, &ebx, &ecx, &edx);
family = (fms >> 8) & 0xf;
model = (fms >> 4) & 0xf;
if (family == 6 || family == 0xf)
@@ -1289,7 +1293,7 @@ void early_cpuid(void)
bdx_highest_ratio = msr & 0xFF;
}

- __get_cpuid(0x6, &eax, &ebx, &ecx, &edx);
+ get_cpuid_or_exit(0x6, &eax, &ebx, &ecx, &edx);
turbo_is_enabled = (eax >> 1) & 1;
has_hwp = (eax >> 7) & 1;
has_epb = (ecx >> 3) & 1;
@@ -1307,7 +1311,7 @@ void parse_cpuid(void)

eax = ebx = ecx = edx = 0;

- __get_cpuid(0, &max_level, &ebx, &ecx, &edx);
+ get_cpuid_or_exit(0, &max_level, &ebx, &ecx, &edx);

if (ebx == 0x756e6547 && edx == 0x49656e69 && ecx == 0x6c65746e)
genuine_intel = 1;
@@ -1316,7 +1320,7 @@ void parse_cpuid(void)
fprintf(stderr, "CPUID(0): %.4s%.4s%.4s ",
(char *)&ebx, (char *)&edx, (char *)&ecx);

- __get_cpuid(1, &fms, &ebx, &ecx, &edx);
+ get_cpuid_or_exit(1, &fms, &ebx, &ecx, &edx);
family = (fms >> 8) & 0xf;
model = (fms >> 4) & 0xf;
stepping = fms & 0xf;
@@ -1341,7 +1345,7 @@ void parse_cpuid(void)
errx(1, "CPUID: no MSR");

- __get_cpuid(0x6, &eax, &ebx, &ecx, &edx);
+ get_cpuid_or_exit(0x6, &eax, &ebx, &ecx, &edx);
/* turbo_is_enabled already set */
/* has_hwp already set */
has_hwp_notify = eax & (1 << 8);
--
2.20.1