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-rw-r--r--src/basic/procfs-util.c268
1 files changed, 268 insertions, 0 deletions
diff --git a/src/basic/procfs-util.c b/src/basic/procfs-util.c
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+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+
+#include "alloc-util.h"
+#include "def.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "parse-util.h"
+#include "process-util.h"
+#include "procfs-util.h"
+#include "stdio-util.h"
+#include "string-util.h"
+
+int procfs_tasks_get_limit(uint64_t *ret) {
+ _cleanup_free_ char *value = NULL;
+ uint64_t pid_max, threads_max;
+ int r;
+
+ assert(ret);
+
+ /* So there are two sysctl files that control the system limit of processes:
+ *
+ * 1. kernel.threads-max: this is probably the sysctl that makes more sense, as it directly puts a limit on
+ * concurrent tasks.
+ *
+ * 2. kernel.pid_max: this limits the numeric range PIDs can take, and thus indirectly also limits the number
+ * of concurrent threads. AFAICS it's primarily a compatibility concept: some crappy old code used a signed
+ * 16bit type for PIDs, hence the kernel provides a way to ensure the PIDs never go beyond INT16_MAX by
+ * default.
+ *
+ * By default #2 is set to much lower values than #1, hence the limit people come into contact with first, as
+ * it's the lowest boundary they need to bump when they want higher number of processes.
+ *
+ * Also note the weird definition of #2: PIDs assigned will be kept below this value, which means the number of
+ * tasks that can be created is one lower, as PID 0 is not a valid process ID. */
+
+ r = read_one_line_file("/proc/sys/kernel/pid_max", &value);
+ if (r < 0)
+ return r;
+
+ r = safe_atou64(value, &pid_max);
+ if (r < 0)
+ return r;
+
+ value = mfree(value);
+ r = read_one_line_file("/proc/sys/kernel/threads-max", &value);
+ if (r < 0)
+ return r;
+
+ r = safe_atou64(value, &threads_max);
+ if (r < 0)
+ return r;
+
+ /* Subtract one from pid_max, since PID 0 is not a valid PID */
+ *ret = MIN(pid_max-1, threads_max);
+ return 0;
+}
+
+int procfs_tasks_set_limit(uint64_t limit) {
+ char buffer[DECIMAL_STR_MAX(uint64_t)+1];
+ _cleanup_free_ char *value = NULL;
+ uint64_t pid_max;
+ int r;
+
+ if (limit == 0) /* This makes no sense, we are userspace and hence count as tasks too, and we want to live,
+ * hence the limit conceptually has to be above 0. Also, most likely if anyone asks for a zero
+ * limit he/she probably means "no limit", hence let's better refuse this to avoid
+ * confusion. */
+ return -EINVAL;
+
+ /* The Linux kernel doesn't allow this value to go below 20, hence don't allow this either, higher values than
+ * TASKS_MAX are not accepted by the pid_max sysctl. We'll treat anything this high as "unbounded" and hence
+ * set it to the maximum. */
+ limit = CLAMP(limit, 20U, TASKS_MAX);
+
+ r = read_one_line_file("/proc/sys/kernel/pid_max", &value);
+ if (r < 0)
+ return r;
+ r = safe_atou64(value, &pid_max);
+ if (r < 0)
+ return r;
+
+ /* As pid_max is about the numeric pid_t range we'll bump it if necessary, but only ever increase it, never
+ * decrease it, as threads-max is the much more relevant sysctl. */
+ if (limit > pid_max-1) {
+ sprintf(buffer, "%" PRIu64, limit+1); /* Add one, since PID 0 is not a valid PID */
+ r = write_string_file("/proc/sys/kernel/pid_max", buffer, WRITE_STRING_FILE_DISABLE_BUFFER);
+ if (r < 0)
+ return r;
+ }
+
+ sprintf(buffer, "%" PRIu64, limit);
+ r = write_string_file("/proc/sys/kernel/threads-max", buffer, WRITE_STRING_FILE_DISABLE_BUFFER);
+ if (r < 0) {
+ uint64_t threads_max;
+
+ /* Hmm, we couldn't write this? If so, maybe it was already set properly? In that case let's not
+ * generate an error */
+
+ value = mfree(value);
+ if (read_one_line_file("/proc/sys/kernel/threads-max", &value) < 0)
+ return r; /* return original error */
+
+ if (safe_atou64(value, &threads_max) < 0)
+ return r; /* return original error */
+
+ if (MIN(pid_max-1, threads_max) != limit)
+ return r; /* return original error */
+
+ /* Yay! Value set already matches what we were trying to set, hence consider this a success. */
+ }
+
+ return 0;
+}
+
+int procfs_tasks_get_current(uint64_t *ret) {
+ _cleanup_free_ char *value = NULL;
+ const char *p, *nr;
+ size_t n;
+ int r;
+
+ assert(ret);
+
+ r = read_one_line_file("/proc/loadavg", &value);
+ if (r < 0)
+ return r;
+
+ /* Look for the second part of the fourth field, which is separated by a slash from the first part. None of the
+ * earlier fields use a slash, hence let's use this to find the right spot. */
+ p = strchr(value, '/');
+ if (!p)
+ return -EINVAL;
+
+ p++;
+ n = strspn(p, DIGITS);
+ nr = strndupa(p, n);
+
+ return safe_atou64(nr, ret);
+}
+
+static uint64_t calc_gcd64(uint64_t a, uint64_t b) {
+
+ while (b > 0) {
+ uint64_t t;
+
+ t = a % b;
+
+ a = b;
+ b = t;
+ }
+
+ return a;
+}
+
+int procfs_cpu_get_usage(nsec_t *ret) {
+ _cleanup_free_ char *first_line = NULL;
+ unsigned long user_ticks, nice_ticks, system_ticks, irq_ticks, softirq_ticks,
+ guest_ticks = 0, guest_nice_ticks = 0;
+ long ticks_per_second;
+ uint64_t sum, gcd, a, b;
+ const char *p;
+ int r;
+
+ assert(ret);
+
+ r = read_one_line_file("/proc/stat", &first_line);
+ if (r < 0)
+ return r;
+
+ p = first_word(first_line, "cpu");
+ if (!p)
+ return -EINVAL;
+
+ if (sscanf(p, "%lu %lu %lu %*u %*u %lu %lu %*u %lu %lu",
+ &user_ticks,
+ &nice_ticks,
+ &system_ticks,
+ &irq_ticks,
+ &softirq_ticks,
+ &guest_ticks,
+ &guest_nice_ticks) < 5) /* we only insist on the first five fields */
+ return -EINVAL;
+
+ ticks_per_second = sysconf(_SC_CLK_TCK);
+ if (ticks_per_second < 0)
+ return -errno;
+ assert(ticks_per_second > 0);
+
+ sum = (uint64_t) user_ticks + (uint64_t) nice_ticks + (uint64_t) system_ticks +
+ (uint64_t) irq_ticks + (uint64_t) softirq_ticks +
+ (uint64_t) guest_ticks + (uint64_t) guest_nice_ticks;
+
+ /* Let's reduce this fraction before we apply it to avoid overflows when converting this to µsec */
+ gcd = calc_gcd64(NSEC_PER_SEC, ticks_per_second);
+
+ a = (uint64_t) NSEC_PER_SEC / gcd;
+ b = (uint64_t) ticks_per_second / gcd;
+
+ *ret = DIV_ROUND_UP((nsec_t) sum * (nsec_t) a, (nsec_t) b);
+ return 0;
+}
+
+int procfs_memory_get(uint64_t *ret_total, uint64_t *ret_used) {
+ uint64_t mem_total = UINT64_MAX, mem_free = UINT64_MAX;
+ _cleanup_fclose_ FILE *f = NULL;
+ int r;
+
+ f = fopen("/proc/meminfo", "re");
+ if (!f)
+ return -errno;
+
+ for (;;) {
+ _cleanup_free_ char *line = NULL;
+ uint64_t *v;
+ char *p, *e;
+ size_t n;
+
+ r = read_line(f, LONG_LINE_MAX, &line);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -EINVAL; /* EOF: Couldn't find one or both fields? */
+
+ p = first_word(line, "MemTotal:");
+ if (p)
+ v = &mem_total;
+ else {
+ p = first_word(line, "MemFree:");
+ if (p)
+ v = &mem_free;
+ else
+ continue;
+ }
+
+ /* Determine length of numeric value */
+ n = strspn(p, DIGITS);
+ if (n == 0)
+ return -EINVAL;
+ e = p + n;
+
+ /* Ensure the line ends in " kB" */
+ n = strspn(e, WHITESPACE);
+ if (n == 0)
+ return -EINVAL;
+ if (!streq(e + n, "kB"))
+ return -EINVAL;
+
+ *e = 0;
+ r = safe_atou64(p, v);
+ if (r < 0)
+ return r;
+ if (*v == UINT64_MAX)
+ return -EINVAL;
+
+ if (mem_total != UINT64_MAX && mem_free != UINT64_MAX)
+ break;
+ }
+
+ if (mem_free > mem_total)
+ return -EINVAL;
+
+ if (ret_total)
+ *ret_total = mem_total * 1024U;
+ if (ret_used)
+ *ret_used = (mem_total - mem_free) * 1024U;
+ return 0;
+}