Prevent channel buffer allocation larger than memory

[lttng-tools.git] / src / common / utils.c

diff --git a/src/common/utils.c b/src/common/utils.c
index a092d940f422979b724fa5a61a72365c54b83ad7..4c000e9b400864591a5bbd7715c2db7e3a1aef26 100644 (file)
--- a/src/common/utils.c
+++ b/src/common/utils.c
@@ -33,6 +33,7 @@
 #include <unistd.h>
 
 #include <common/common.h>
+#include <common/readwrite.h>
 #include <common/runas.h>
 #include <common/compat/getenv.h>
 #include <common/compat/string.h>
@@ -43,6 +44,19 @@
 #include "defaults.h"
 #include "time.h"
 
+#define PROC_MEMINFO_PATH               "/proc/meminfo"
+#define PROC_MEMINFO_MEMAVAILABLE_LINE  "MemAvailable:"
+#define PROC_MEMINFO_MEMTOTAL_LINE      "MemTotal:"
+
+/* The length of the longest field of `/proc/meminfo`. */
+#define PROC_MEMINFO_FIELD_MAX_NAME_LEN        20
+
+#if (PROC_MEMINFO_FIELD_MAX_NAME_LEN == 20)
+#define MAX_NAME_LEN_SCANF_IS_A_BROKEN_API "19"
+#else
+#error MAX_NAME_LEN_SCANF_IS_A_BROKEN_API must be updated to match (PROC_MEMINFO_FIELD_MAX_NAME_LEN - 1)
+#endif
+
 /*
  * Return a partial realpath(3) of the path even if the full path does not
  * exist. For instance, with /tmp/test1/test2/test3, if test2/ does not exist
@@ -1673,3 +1687,77 @@ int utils_show_help(int section, const char *page_name,
 end:
        return ret;
 }
+
+static
+int read_proc_meminfo_field(const char *field, size_t *value)
+{
+       int ret;
+       FILE *proc_meminfo;
+       char name[PROC_MEMINFO_FIELD_MAX_NAME_LEN] = {};
+
+       proc_meminfo = fopen(PROC_MEMINFO_PATH, "r");
+       if (!proc_meminfo) {
+               PERROR("Failed to fopen() " PROC_MEMINFO_PATH);
+               ret = -1;
+               goto fopen_error;
+        }
+
+       /*
+        * Read the contents of /proc/meminfo line by line to find the right
+        * field.
+        */
+       while (!feof(proc_meminfo)) {
+               unsigned long value_kb;
+
+               ret = fscanf(proc_meminfo,
+                               "%" MAX_NAME_LEN_SCANF_IS_A_BROKEN_API "s %lu kB\n",
+                               name, &value_kb);
+               if (ret == EOF) {
+                       /*
+                        * fscanf() returning EOF can indicate EOF or an error.
+                        */
+                       if (ferror(proc_meminfo)) {
+                               PERROR("Failed to parse " PROC_MEMINFO_PATH);
+                       }
+                       break;
+               }
+
+               if (ret == 2 && strcmp(name, field) == 0) {
+                       /*
+                        * This number is displayed in kilo-bytes. Return the
+                        * number of bytes.
+                        */
+                       *value = ((size_t) value_kb) * 1024;
+                       ret = 0;
+                       goto found;
+               }
+       }
+       /* Reached the end of the file without finding the right field. */
+       ret = -1;
+
+found:
+       fclose(proc_meminfo);
+fopen_error:
+       return ret;
+}
+
+/*
+ * Returns an estimate of the number of bytes of memory available based on the
+ * the information in `/proc/meminfo`. The number returned by this function is
+ * a best guess.
+ */
+LTTNG_HIDDEN
+int utils_get_memory_available(size_t *value)
+{
+       return read_proc_meminfo_field(PROC_MEMINFO_MEMAVAILABLE_LINE, value);
+}
+
+/*
+ * Returns the total size of the memory on the system in bytes based on the
+ * the information in `/proc/meminfo`.
+ */
+LTTNG_HIDDEN
+int utils_get_memory_total(size_t *value)
+{
+       return read_proc_meminfo_field(PROC_MEMINFO_MEMTOTAL_LINE, value);
+}