[PATCH 0/18] x86_energy_perf_policy cleanups

[PATCH 0/18] x86_energy_perf_policy cleanups

[Len Brown]

This batch is mostly the result of an experiment to see if AI
is good enough to find issues, then fix and document them.

Turned out that AI has its strengths, and its weaknesses,
and figuring out which is which can be tedious.

Bonus: If you find issues in this series,
you can claim you are smarter than AI.  (Andy Shevchenko is:-)

thanks,
Len Brown
Intel Open Source Technology Center

[PATCH 01/18] x86_energy_perf_policy: Create msr_path helper
[PATCH 02/18] x86_energy_perf_policy: Enhance MSR probe
[PATCH 03/18] x86_energy_perf_policy: Prevent unlikely buffer
[PATCH 04/18] x86_energy_perf_policy: Cleanup: Harden with strtol()
[PATCH 05/18] x86_energy_perf_policy: Cleanup: Use snprintf() for
[PATCH 06/18] x86_energy_perf_policy: Fix optarg keyword matching
[PATCH 07/18] x86_energy_perf_policy: Cleanup: Fix potential ratio
[PATCH 08/18] x86_energy_perf_policy: Bound package iteration
[PATCH 09/18] x86_energy_perf_policy: Cleanup: Define HWP window max
[PATCH 10/18] x86_energy_perf_policy: Cleanup: Define BCLK_MHZ
[PATCH 11/18] x86_energy_perf_policy: Cleanup: Check fseek() in VM
[PATCH 12/18] x86_energy_perf_policy: Document MSRHEADER
[PATCH 13/18] x86_energy_perf_policy: Cleanup: Drop unused signal.h
[PATCH 14/18] x86_energy_perf_policy: Cleanup: Constify profile name
[PATCH 15/18] x86_energy_perf_policy: Cleanup: Constify HWP strings
[PATCH 16/18] x86_energy_perf_policy: Fix use-after-free in
[PATCH 17/18] x86_energy_perf_policy: Fix write_sysfs() return type
[PATCH 18/18] MAINTAINERS: Add x86_energy_perf_policy

[PATCH 01/18] x86_energy_perf_policy: Create msr_path helper

[Len Brown]

From: Len Brown <len.brown@intel.com>

Factor out code that creates msr_path[].

No functional change.

Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86_energy_perf_policy.c                  | 38 +++++++++++--------
 1 file changed, 23 insertions(+), 15 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 0dc959e30076..a963c0430794 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
@@ -98,6 +98,7 @@ unsigned char update_platform_profile;
 int soc_slider_balance;
 int soc_slider_offset;
 char platform_profile[64];
+char msr_path[64];
 
 #define PATH_TO_CPU "/sys/devices/system/cpu/"
 #define SYSFS_PATH_MAX 255
@@ -799,21 +800,31 @@ void err_on_hypervisor(void)
 		err(-1, "not supported on this virtual machine");
 }
 
+/*
+ * The Linux MSR driver uses offsets into /dev/cpu/{cpu#}/msr
+ * Some Android versions uses an incompatible path: /dev/msr{cpu#}
+ * Probe and prefer the Linux path, use Android if Linux does not work.
+ */
+static void set_msr_path(int cpu)
+{
+	if (snprintf(msr_path, sizeof(msr_path), use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", cpu) >= (int)sizeof(msr_path))
+		err(-1, "MSR path buffer overflow for cpu%d", cpu);
+}
+
 int get_msr(int cpu, int offset, unsigned long long *msr)
 {
 	int retval;
-	char pathname[32];
 	int fd;
 
-	sprintf(pathname, use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", cpu);
-	fd = open(pathname, O_RDONLY);
+	set_msr_path(cpu);
+	fd = open(msr_path, O_RDONLY);
 	if (fd < 0)
-		err(-1, "%s open failed, try chown or chmod +r %s, or run as root", pathname, use_android_msr_path ? "/dev/msr*" : "/dev/cpu/*/msr");
+		err(-1, "%s open failed, try chown or chmod +r, or run as root", msr_path);
 
 	retval = pread(fd, msr, sizeof(*msr), offset);
 	if (retval != sizeof(*msr)) {
 		err_on_hypervisor();
-		err(-1, "%s offset 0x%llx read failed", pathname, (unsigned long long)offset);
+		err(-1, "%s offset 0x%llx read failed", msr_path, (unsigned long long)offset);
 	}
 
 	if (debug > 1)
@@ -825,14 +836,13 @@ int get_msr(int cpu, int offset, unsigned long long *msr)
 
 int put_msr(int cpu, int offset, unsigned long long new_msr)
 {
-	char pathname[32];
 	int retval;
 	int fd;
 
-	sprintf(pathname, use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", cpu);
-	fd = open(pathname, O_RDWR);
+	set_msr_path(cpu);
+	fd = open(msr_path, O_RDWR);
 	if (fd < 0)
-		err(-1, "%s open failed, try chown or chmod +r %s, or run as root", pathname, use_android_msr_path ? "/dev/msr*" : "/dev/cpu/*/msr");
+		err(-1, "%s open failed, try chown or chmod +r, or run as root", msr_path);
 
 	retval = pwrite(fd, &new_msr, sizeof(new_msr), offset);
 	if (retval != sizeof(new_msr))
@@ -1604,22 +1614,20 @@ void set_base_cpu(void)
 static void probe_android_msr_path(void)
 {
 	struct stat sb;
-	char test_path[32];
 
-	sprintf(test_path, "/dev/msr%d", base_cpu);
-	if (stat(test_path, &sb) == 0)
+	set_msr_path(base_cpu);	/* called with use_android_path = 0, to probe Linux path */
+	if (stat(msr_path, &sb))
 		use_android_msr_path = 1;
 }
 
 void probe_dev_msr(void)
 {
 	struct stat sb;
-	char pathname[32];
 
 	probe_android_msr_path();
 
-	sprintf(pathname, use_android_msr_path ? "/dev/msr%d" : "/dev/cpu/%d/msr", base_cpu);
-	if (stat(pathname, &sb)) {
+	set_msr_path(base_cpu);
+	if (stat(msr_path, &sb)) {
 		if (system("/sbin/modprobe msr > /dev/null 2>&1")) {
 			if (use_android_msr_path)
 				err(-5, "no /dev/msr0, Try \"# modprobe msr\" ");
-- 
2.45.2

[PATCH 02/18] x86_energy_perf_policy: Enhance MSR probe

[Len Brown]

From: Len Brown <len.brown@intel.com>

If Linux MSR driver isn't running,
modprobe and try the Linux path again.
If still no joy, try Android path.

Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86_energy_perf_policy.c                  | 40 ++++++++++++-------
 1 file changed, 26 insertions(+), 14 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 a963c0430794..abd3cf2fdd39 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
@@ -15,6 +15,7 @@
 #include <sys/types.h>
 #include <sched.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <sys/resource.h>
 #include <getopt.h>
 #include <err.h>
@@ -1611,30 +1612,41 @@ void set_base_cpu(void)
 		err(-ENODEV, "No valid cpus found");
 }
 
-static void probe_android_msr_path(void)
+/* return 0 if path exists */
+static int check_msr_path(void)
 {
 	struct stat sb;
 
-	set_msr_path(base_cpu);	/* called with use_android_path = 0, to probe Linux path */
-	if (stat(msr_path, &sb))
-		use_android_msr_path = 1;
+	return stat(msr_path, &sb);
 }
 
+/*
+ * Check Linux MSR path
+ * If it fails, try modprobe and check it again
+ * If still no joy, enable Android path and try again
+ */
 void probe_dev_msr(void)
 {
-	struct stat sb;
+	int retval;
+
+	use_android_msr_path = 0;
+	set_msr_path(base_cpu);
+	if (check_msr_path() == 0)
+		return;
 
-	probe_android_msr_path();
+	retval = system("/sbin/modprobe msr > /dev/null 2>&1");
 
+	if (check_msr_path() == 0)
+		return;
+
+	use_android_msr_path = 1;
 	set_msr_path(base_cpu);
-	if (stat(msr_path, &sb)) {
-		if (system("/sbin/modprobe msr > /dev/null 2>&1")) {
-			if (use_android_msr_path)
-				err(-5, "no /dev/msr0, Try \"# modprobe msr\" ");
-			else
-				err(-5, "no /dev/cpu/0/msr, Try \"# modprobe msr\" ");
-		}
-	}
+	if (check_msr_path() == 0)
+		return;
+
+	if (WIFEXITED(retval))
+		retval = WEXITSTATUS(retval);
+	err(-1, "\"msr\" driver support required, modprobe msr returned %d", retval);
 }
 
 static void get_cpuid_or_exit(unsigned int leaf, unsigned int *eax, unsigned int *ebx, unsigned int *ecx, unsigned int *edx)
-- 
2.45.2

[PATCH 03/18] x86_energy_perf_policy: Prevent unlikely buffer overflow

[Len Brown]

From: Len Brown <len.brown@intel.com>

Protect update_cpufreq_scaling_freq() from buffer overflow
if somehow it was called with a huge CPU number.

Fixes: f1c35c73191b ("tools/power x86_energy_perf_policy: Version 2026.04.25")
Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 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 abd3cf2fdd39..3c4e376f6c77 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
@@ -1166,12 +1166,12 @@ int ratio_2_sysfs_khz(int ratio)
  */
 void update_cpufreq_scaling_freq(int is_max, int cpu, unsigned int ratio)
 {
-	char pathname[64];
+	char pathname[96];
 	FILE *fp;
 	int retval;
 	int khz;
 
-	sprintf(pathname, "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_%s_freq", cpu, is_max ? "max" : "min");
+	snprintf(pathname, sizeof(pathname), "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_%s_freq", cpu, is_max ? "max" : "min");
 
 	fp = fopen(pathname, "w");
 	if (!fp) {
-- 
2.45.2

[PATCH 04/18] x86_energy_perf_policy: Cleanup: Harden with strtol()

[Len Brown]

From: Len Brown <len.brown@intel.com>

Replace atoi() with strtol() and proper error checking when parsing the
--hwp-use-pkg command-line argument value, and other spots.

Also add explicit check that value is in valid range [0, 1].

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86_energy_perf_policy.c                  | 46 +++++++++++--------
 1 file changed, 26 insertions(+), 20 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 3c4e376f6c77..98e5aa9aec51 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
@@ -191,7 +191,7 @@ int parse_cmdline_epb(int i)
 		return ENERGY_PERF_BIAS_PERFORMANCE;
 	}
 	if (i < 0 || i > ENERGY_PERF_BIAS_POWERSAVE)
-		errx(1, "--epb must be from 0 to 15");
+		errx(1, "--epb must be 0 through 15");
 	return i;
 }
 
@@ -305,8 +305,8 @@ int parse_cmdline_hwp_epp(int i)
 	case OPTARG_PERFORMANCE:
 		return HWP_EPP_PERFORMANCE;
 	}
-	if (i < 0 || i > 0xff) {
-		fprintf(stderr, "--hwp-epp must be from 0 to 0xff\n");
+	if (i < 0 || i > 255) {
+		fprintf(stderr, "--hwp-epp must be 0 through 255\n");
 		usage();
 	}
 	return i;
@@ -355,19 +355,13 @@ int parse_optarg_string(char *s)
 	if (!strncmp(s, "performance", 11))
 		return OPTARG_PERFORMANCE;
 
+	errno = 0;
 	i = strtol(s, &endptr, 0);
-	if (s == endptr) {
-		fprintf(stderr, "no digits in \"%s\"\n", s);
+	if (endptr == s || errno == ERANGE || i < 0 || i > 256) {
+		warnx("bad value \"%s\"\n", s);
 		usage();
 	}
-	if (i == LONG_MIN || i == LONG_MAX)
-		errx(-1, "%s", s);
 
-	if (i > 0xFF)
-		errx(-1, "%d (0x%x) must be < 256", i, i);
-
-	if (i < 0)
-		errx(-1, "%d (0x%x) must be >= 0", i, i);
 	return i;
 }
 
@@ -425,7 +419,7 @@ void parse_cmdline_cpu(char *s)
 
 			startp++;
 			end_cpu = strtol(startp, &endp, 10);
-			if (startp == endp)
+			if (endp == startp)
 				continue;
 
 			while (cpu <= end_cpu) {
@@ -469,11 +463,11 @@ void parse_cmdline_cpu(char *s)
 				break;
 		}
 
+		errno = 0;
 		cpu = strtol(startp, &endp, 10);
-		if (startp == endp)
+		if (endp == startp || errno == ERANGE || cpu < 0 || cpu > max_cpu_num)
 			errx(1, "--cpu cpu-set: confused by '%s'", startp);
-		if (cpu > max_cpu_num)
-			errx(1, "Requested cpu%d exceeds max cpu%d", cpu, max_cpu_num);
+
 		CPU_SET_S(cpu, cpu_setsize, cpu_selected_set);
 		startp = endp;
 	}
@@ -505,7 +499,7 @@ void parse_cmdline_pkg(char *s)
 
 			startp++;
 			end_pkg = strtol(startp, &endp, 10);
-			if (startp == endp)
+			if (endp == startp)
 				continue;
 
 			while (pkg <= end_pkg) {
@@ -526,6 +520,7 @@ void parse_cmdline_pkg(char *s)
 		pkg = strtol(startp, &endp, 10);
 		if (pkg > max_pkg_num)
 			errx(1, "Requested pkg%d Exceeds max pkg%d", pkg, max_pkg_num);
+
 		pkg_selected_set |= 1 << pkg;
 		startp = endp;
 	}
@@ -546,6 +541,7 @@ static int parse_cmdline_int(const char *s, int *out)
 	char *endp;
 	long val;
 
+	errno = 0;
 	val = strtol(s, &endp, 0);
 	if (endp == s || errno == ERANGE)
 		return -1;
@@ -716,7 +712,15 @@ void cmdline(int argc, char **argv)
 			break;
 		case 'u':
 			update_hwp_use_pkg++;
-			if (atoi(optarg) == 0)
+			char *endp;
+			long val;
+
+			errno = 0;
+			val = strtol(optarg, &endp, 10);
+			if (endp == optarg || errno == ERANGE || val < 0 || val > 1)
+				errx(1, "--hwp-use-pkg: must be 0 or 1");
+
+			if (val == 0)
 				req_update.hwp_use_pkg = 0;
 			else
 				req_update.hwp_use_pkg = 1;
@@ -1015,8 +1019,9 @@ static int get_epb_sysfs(int cpu)
 	if (!read_sysfs(path, linebuf, 3))
 		return -1;
 
+	errno = 0;
 	val = strtol(linebuf, &endp, 0);
-	if (endp == linebuf || errno == ERANGE)
+	if (endp == linebuf || errno == ERANGE || val < 0 || val > 15)
 		return -1;
 
 	return (int)val;
@@ -1039,8 +1044,9 @@ static int set_epb_sysfs(int cpu, int val)
 	if (ret <= 0)
 		return -1;
 
+	errno = 0;
 	val = strtol(linebuf, &endp, 0);
-	if (endp == linebuf || errno == ERANGE)
+	if (endp == linebuf || errno == ERANGE || val < 0 || val > 15)
 		return -1;
 
 	return (int)val;
-- 
2.45.2

[PATCH 05/18] x86_energy_perf_policy: Cleanup: Use snprintf() for platform-profile

[Len Brown]

From: Len Brown <len.brown@intel.com>

Better hygiene to use snprintf() instead of strcpy().

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 98e5aa9aec51..8ce47d46eedf 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
@@ -675,7 +675,7 @@ void cmdline(int argc, char **argv)
 				errx(1, "--platform-profile: value too long");
 			if (!platform_profile_access(W_OK))
 				errx(1, "Can not update platform-profile in '%s'", PATH_PLATFORM_PROFILE);
-			strcpy(platform_profile, optarg);
+			snprintf(platform_profile, sizeof(platform_profile), "%s", optarg);
 			update_platform_profile = 1;
 			break;
 		case 'm':
-- 
2.45.2

[PATCH 06/18] x86_energy_perf_policy: Fix optarg keyword matching

[Len Brown]

From: Len Brown <len.brown@intel.com>

Replace strncmp() with strcmp() for exact string matching in
parse_optarg_string().  Exact keyword matching is safer and clearer.
This prevents accidental matches with longer strings
like "balance-power-extra".

Fixes: 4beec1d75196 ("tools/power x86_energy_perf_policy: support HWP.EPP")
Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86_energy_perf_policy/x86_energy_perf_policy.c  | 12 ++++++------
 1 file changed, 6 insertions(+), 6 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 8ce47d46eedf..5afff02bf9e7 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
@@ -337,22 +337,22 @@ int parse_optarg_string(char *s)
 	int i;
 	char *endptr;
 
-	if (!strncmp(s, "default", 7))
+	if (strcmp(s, "default") == 0)
 		return OPTARG_NORMAL;
 
-	if (!strncmp(s, "normal", 6))
+	if (strcmp(s, "normal") == 0)
 		return OPTARG_NORMAL;
 
-	if (!strncmp(s, "power", 9))
+	if (strcmp(s, "power") == 0)
 		return OPTARG_POWER;
 
-	if (!strncmp(s, "balance-power", 17))
+	if (strcmp(s, "balance-power") == 0)
 		return OPTARG_BALANCE_POWER;
 
-	if (!strncmp(s, "balance-performance", 19))
+	if (strcmp(s, "balance-performance") == 0)
 		return OPTARG_BALANCE_PERFORMANCE;
 
-	if (!strncmp(s, "performance", 11))
+	if (strcmp(s, "performance") == 0)
 		return OPTARG_PERFORMANCE;
 
 	errno = 0;
-- 
2.45.2

[PATCH 07/18] x86_energy_perf_policy: Cleanup: Fix potential ratio overflow

[Len Brown]

From: Len Brown <len.brown@intel.com>

Prevent integer overflow in ratio_2_msr_perf() by using 64-bit
arithmetic for the intermediate multiplication calculation.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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 5afff02bf9e7..6b0079a0b36c 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
@@ -141,11 +141,13 @@ void usage(void)
 int ratio_2_msr_perf(int ratio)
 {
 	int msr_perf;
+	unsigned long long temp;
 
 	if (!bdx_highest_ratio)
 		return ratio;
 
-	msr_perf = ratio * 255 / bdx_highest_ratio;
+	temp = (unsigned long long)ratio * 255;
+	msr_perf = temp / bdx_highest_ratio;
 
 	if (debug)
 		fprintf(stderr, "%d = ratio_to_msr_perf(%d)\n", msr_perf, ratio);
-- 
2.45.2

[PATCH 08/18] x86_energy_perf_policy: Bound package iteration

[Len Brown]

From: Len Brown <len.brown@intel.com>

Add explicit bounds checking against MAX_PACKAGES in for_packages()
to prevent potential out-of-bounds bit shift operations.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 6b0079a0b36c..5c54cf9e0fcf 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
@@ -532,7 +532,7 @@ void for_packages(unsigned long long pkg_set, int (func) (int))
 {
 	int pkg_num;
 
-	for (pkg_num = 0; pkg_num <= max_pkg_num; ++pkg_num) {
+	for (pkg_num = 0; pkg_num <= max_pkg_num && pkg_num < MAX_PACKAGES; ++pkg_num) {
 		if (pkg_set & (1UL << pkg_num))
 			func(pkg_num);
 	}
-- 
2.45.2

[PATCH 09/18] x86_energy_perf_policy: Cleanup: Define HWP window max

[Len Brown]

From: Len Brown <len.brown@intel.com>

Replace all occurrences of the hardcoded magic number 1270000000
with a named symbolic constant HWP_WINDOW_MAX_USEC to improve code
readability and maintainability.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c    | 7 +++++--
 1 file changed, 5 insertions(+), 2 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 5c54cf9e0fcf..1a0c23cd4cc4 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
@@ -34,6 +34,9 @@
 #define	OPTARG_BALANCE_PERFORMANCE	(INT_MAX - 4)
 #define	OPTARG_PERFORMANCE		(INT_MAX - 5)
 
+/* Maximum HWP activity window duration in microseconds */
+#define HWP_WINDOW_MAX_USEC 1270000000U
+
 struct msr_hwp_cap {
 	unsigned char highest;
 	unsigned char guaranteed;
@@ -273,8 +276,8 @@ int parse_cmdline_hwp_window(int i)
 	case OPTARG_PERFORMANCE:
 		return 0;
 	}
-	if (i < 0 || i > 1270000000) {
-		fprintf(stderr, "--hwp-window: 0 for auto; 1 - 1270000000 usec for window duration\n");
+	if (i < 0 || i > HWP_WINDOW_MAX_USEC) {
+		fprintf(stderr, "--hwp-window: 0 for auto; 1 - %u usec for window duration\n", HWP_WINDOW_MAX_USEC);
 		usage();
 	}
 	for (exponent = 0;; ++exponent) {
-- 
2.45.2

[PATCH 10/18] x86_energy_perf_policy: Cleanup: Define BCLK_MHZ

[Len Brown]

From: Len Brown <len.brown@intel.com>

Replace the hardcoded value 100 with a named symbolic constant BCLK_MHZ in
ratio_2_sysfs_khz() to document the assumed bus clock frequency.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c      | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

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 1a0c23cd4cc4..cfd9d8df6ec1 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
@@ -37,6 +37,9 @@
 /* Maximum HWP activity window duration in microseconds */
 #define HWP_WINDOW_MAX_USEC 1270000000U
 
+/* Nominal bus clock frequency in MHz - assumed for all HWP systems */
+#define BCLK_MHZ 100
+
 struct msr_hwp_cap {
 	unsigned char highest;
 	unsigned char guaranteed;
@@ -1161,7 +1164,7 @@ int print_pkg_msrs(int pkg)
  */
 int ratio_2_sysfs_khz(int ratio)
 {
-	int bclk_khz = 100 * 1000;	/* 100,000 KHz = 100 MHz */
+	int bclk_khz = BCLK_MHZ * 1000; /* Convert MHz to KHz */
 
 	return ratio * bclk_khz;
 }
-- 
2.45.2

[PATCH 11/18] x86_energy_perf_policy: Cleanup: Check fseek() in VM path

[Len Brown]

From: Len Brown <len.brown@intel.com>

Add return value validation for fseek() and ensure consistent
resource cleanup on all error paths in err_on_hypervisor().

Fixes: 0936cdfbb527 ("tools/power x86_energy_perf_policy: Input/output error in a VM")
Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c     | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

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 cfd9d8df6ec1..1343966b1f07 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
@@ -797,7 +797,11 @@ void err_on_hypervisor(void)
 		err(1, "Failed to find 'flags' in /proc/cpuinfo");
 	}
 	rewind(cpuinfo);
-	fseek(cpuinfo, flags - buffer, SEEK_SET);
+	if (fseek(cpuinfo, flags - buffer, SEEK_SET) != 0) {
+		fclose(cpuinfo);
+		free(buffer);
+		err(1, "Failed to seek in /proc/cpuinfo");
+	}
 	if (!fgets(buffer, 4096, cpuinfo)) {
 		fclose(cpuinfo);
 		free(buffer);
-- 
2.45.2

[PATCH 12/18] x86_energy_perf_policy: Document MSRHEADER

[Len Brown]

From: Len Brown <len.brown@intel.com>

Add comprehensive comments documenting the MSRHEADER macro usage and
expected build system configuration.

The MSRHEADER macro is not defined in the source file and must be
provided by the build system (typically as
-DMSRHEADER=\"msr-index.h\" or similar). This can be confusing for
developers building the code independently.

Adding documentation clarifies:
- That MSRHEADER is a macro expected to be defined externally
- What types of headers are typically used
- Example build flags showing how to define it

This prevents build failures and confusion when compiling without
the proper build system context.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c    | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

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 1343966b1f07..fcfdb0075408 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
@@ -9,7 +9,12 @@
  */
 
 #define _GNU_SOURCE
-#include MSRHEADER
+/*
+ * MSRHEADER macro should be defined by the build system to include the
+ * appropriate MSR definitions header file. Typical usage:
+ * gcc -DMSRHEADER=\"msr-index.h\" or similar platform-specific MSR header
+ */
+#include MSRHEADER  /* e.g., msr-index.h with MSR_* constant definitions */
 #include <stdio.h>
 #include <unistd.h>
 #include <sys/types.h>
-- 
2.45.2

[PATCH 13/18] x86_energy_perf_policy: Cleanup: Drop unused signal.h

[Len Brown]

From: Len Brown <len.brown@intel.com>

Remove unused #include <signal.h>

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 1 -
 1 file changed, 1 deletion(-)

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 fcfdb0075408..e26a28fc7edd 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
@@ -25,7 +25,6 @@
 #include <getopt.h>
 #include <err.h>
 #include <fcntl.h>
-#include <signal.h>
 #include <sys/time.h>
 #include <limits.h>
 #include <stdlib.h>
-- 
2.45.2

[PATCH 14/18] x86_energy_perf_policy: Cleanup: Constify profile name arg

[Len Brown]

From: Len Brown <len.brown@intel.com>

Add const qualifier to the name parameter of
platform_profile_name_is() which is read-only.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 e26a28fc7edd..ffdc5df27ef1 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
@@ -582,7 +582,7 @@ static int platform_profile_access(int mode)
 	return 1;
 }
 
-static int platform_profile_name_is(char *name)
+static int platform_profile_name_is(const char *name)
 {
 	char buf[64];
 
-- 
2.45.2

[PATCH 15/18] x86_energy_perf_policy: Cleanup: Constify HWP strings

[Len Brown]

From: Len Brown <len.brown@intel.com>

Add const qualifiers to the string parameters of parse_optarg_string(),
print_hwp_request(), and print_hwp_request_pkg() which are read-only.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c     | 6 +++---
 1 file changed, 3 insertions(+), 3 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 ffdc5df27ef1..70d889c3e0dc 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
@@ -344,7 +344,7 @@ int parse_cmdline_turbo(int i)
 	return i;
 }
 
-int parse_optarg_string(char *s)
+int parse_optarg_string(const char *s)
 {
 	int i;
 	char *endptr;
@@ -965,7 +965,7 @@ void read_hwp_cap(int cpu, struct msr_hwp_cap *cap, unsigned int msr_offset)
 	cap->lowest = msr_perf_2_ratio(HWP_LOWEST_PERF(msr));
 }
 
-void print_hwp_request(int cpu, struct msr_hwp_request *h, char *str)
+void print_hwp_request(int cpu, struct msr_hwp_request *h, const char *str)
 {
 	if (cpu != -1)
 		printf("cpu%d: ", cpu);
@@ -977,7 +977,7 @@ void print_hwp_request(int cpu, struct msr_hwp_request *h, char *str)
 	       h->hwp_min, h->hwp_max, h->hwp_desired, h->hwp_epp, h->hwp_window, h->hwp_window & 0x7F, (h->hwp_window >> 7) & 0x7, h->hwp_use_pkg);
 }
 
-void print_hwp_request_pkg(int pkg, struct msr_hwp_request *h, char *str)
+void print_hwp_request_pkg(int pkg, struct msr_hwp_request *h, const char *str)
 {
 	printf("pkg%d: ", pkg);
 
-- 
2.45.2

[PATCH 16/18] x86_energy_perf_policy: Fix use-after-free in err_on_hypervisor()

[Len Brown]

From: Len Brown <len.brown@intel.com>

Avoid testing a pointer into a freed buffer.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c  | 9 ++++-----
 1 file changed, 4 insertions(+), 5 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 70d889c3e0dc..f8ab9f4465ce 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
@@ -782,10 +782,10 @@ void err_on_hypervisor(void)
 	/* On VMs /proc/cpuinfo contains a "flags" entry for hypervisor */
 	cpuinfo = fopen_or_die("/proc/cpuinfo", "r");
 
-	buffer = malloc(4096);
+	buffer = calloc(4096, 1);
 	if (!buffer) {
 		fclose(cpuinfo);
-		err(-ENOMEM, "buffer malloc fail");
+		err(-ENOMEM, "buffer calloc fail");
 	}
 
 	if (!fread(buffer, 1024, 1, cpuinfo)) {
@@ -814,11 +814,10 @@ void err_on_hypervisor(void)
 	fclose(cpuinfo);
 
 	hypervisor = strstr(buffer, "hypervisor");
-
-	free(buffer);
-
 	if (hypervisor)
 		err(-1, "not supported on this virtual machine");
+
+	free(buffer);
 }
 
 /*
-- 
2.45.2

[PATCH 17/18] x86_energy_perf_policy: Fix write_sysfs() return type

[Len Brown]

From: Amarjeet <amarjeet@intel.com>

write_sysfs() returns an unsigned int even though it returns -1 when
write() fails. This converts the error to UINT_MAX and can cause callers
that treat a nonzero return value as success to miss the failure.

Use ssize_t to match write(), update the receiving variable accordingly,
and explicitly require a positive result in sysfs_write_string().

Signed-off-by: Amarjeet <amarjeet@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c   | 8 ++++----
 1 file changed, 4 insertions(+), 4 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 f8ab9f4465ce..89850cbc6d90 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
@@ -897,7 +897,7 @@ static unsigned int read_sysfs(const char *path, char *buf, size_t buflen)
 	return (unsigned int)numread;
 }
 
-static unsigned int write_sysfs(const char *path, char *buf, size_t buflen)
+static ssize_t write_sysfs(const char *path, char *buf, size_t buflen)
 {
 	ssize_t numwritten;
 	int fd;
@@ -916,7 +916,7 @@ static unsigned int write_sysfs(const char *path, char *buf, size_t buflen)
 
 	close(fd);
 
-	return (unsigned int)numwritten;
+	return numwritten;
 }
 
 static int sysfs_read_string(const char *path, char *buf, size_t buflen)
@@ -941,7 +941,7 @@ static int sysfs_write_string(const char *path, const char *buf)
 	len = snprintf(tmp, sizeof(tmp), "%s\n", buf);
 	if (len < 0 || len >= (int)sizeof(tmp))
 		return -1;
-	return write_sysfs(path, tmp, (size_t)len + 1) ? 0 : -1;
+	return write_sysfs(path, tmp, (size_t)len + 1) > 0 ? 0 : -1;
 }
 
 void print_hwp_cap(int cpu, struct msr_hwp_cap *cap, char *str)
@@ -1047,7 +1047,7 @@ static int set_epb_sysfs(int cpu, int val)
 	char path[SYSFS_PATH_MAX];
 	char linebuf[3];
 	char *endp;
-	int ret;
+	ssize_t ret;
 
 	if (!has_epb)
 		return -1;
-- 
2.45.2

[PATCH 18/18] MAINTAINERS: Add x86_energy_perf_policy

[Len Brown]

From: Len Brown <len.brown@intel.com>

This entry should help direct patches to linux-pm.
(rather than to lkml)

Signed-off-by: Len Brown <len.brown@intel.com>
---
 MAINTAINERS | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 782389bd5cd3..3958e66188ec 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -29577,6 +29577,15 @@ W:	https://x86-cpuid.org
 F:	arch/x86/include/asm/cpuid/leaf_types.h
 F:	tools/arch/x86/kcpuid/
 
+X86 ENERGY PERF POLICY UTILITY
+M:	Len Brown <lenb@kernel.org>
+L:	linux-pm@vger.kernel.org
+S:	Supported
+Q:	https://patchwork.kernel.org/project/linux-pm/list/
+B:	https://bugzilla.kernel.org
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux.git x86_energy_perf_policy
+F:	tools/power/x86/x86_energy_perf_policy/
+
 X86 ENTRY CODE
 M:	Andy Lutomirski <luto@kernel.org>
 L:	linux-kernel@vger.kernel.org
-- 
2.45.2

Re: [PATCH 01/18] x86_energy_perf_policy: Create msr_path helper

[Andy Shevchenko]

On Mon, Oct 19, 2026 at 12:43:22PM -0400, Len Brown wrote:

> Factor out code that creates msr_path[].
> 
> No functional change.
> 
> Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6

In July IIRC the kernel documentation was updated to make the

Assisted-by: LLM

be a standard for the kernel contributions independently on the model(s) in use.
Yeah, I only learnt like a month ago about this development.

> Signed-off-by: Len Brown <len.brown@intel.com>

The rest I have reviewed (as the tag above suggests).

-- 
With Best Regards,
Andy Shevchenko