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authorSiddhesh Poyarekar <siddhesh@sourceware.org>2016-12-31 23:33:27 +0530
committerSiddhesh Poyarekar <siddhesh@sourceware.org>2016-12-31 23:49:24 +0530
commit9dd409a5f4a7a053cc962f8371dad0fe5cc22597 (patch)
treea205733e557ccf0b66021deff34cd6b690150f9e /elf
parent67e58f39412ecd4467034761f3f074283c90f3c8 (diff)
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Initialize tunable list with the GLIBC_TUNABLES environment variable
Read tunables values from the users using the GLIBC_TUNABLES environment variable. The value of this variable is a colon-separated list of name=value pairs. So a typical string would look like this: GLIBC_TUNABLES=glibc.malloc.mmap_threshold=2048:glibc.malloc.trim_threshold=1024 * config.make.in (have-loop-to-function): Define. * elf/Makefile (CFLAGS-dl-tunables.c): Add -fno-tree-loop-distribute-patterns. * elf/dl-tunables.c: Include libc-internals.h. (GLIBC_TUNABLES): New macro. (tunables_strdup): New function. (parse_tunables): New function. (min_strlen): New function. (__tunables_init): Use the new functions and macro. (disable_tunable): Disable tunable from GLIBC_TUNABLES. * malloc/tst-malloc-usable-tunables.c: New test case. * malloc/tst-malloc-usable-static-tunables.c: New test case. * malloc/Makefile (tests, tests-static): Add tests.
Diffstat (limited to 'elf')
-rw-r--r--elf/Makefile6
-rw-r--r--elf/dl-tunables.c129
2 files changed, 134 insertions, 1 deletions
diff --git a/elf/Makefile b/elf/Makefile
index de28d99..3cda2c9 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -38,6 +38,12 @@ endif
ifeq (yes,$(have-tunables))
dl-routines += dl-tunables
+
+# Make sure that the compiler does not insert any library calls in tunables
+# code paths.
+ifeq (yes,$(have-loop-to-function))
+CFLAGS-dl-tunables.c = -fno-tree-loop-distribute-patterns
+endif
endif
all-dl-routines = $(dl-routines) $(sysdep-dl-routines)
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 472747b..8d69140 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -30,7 +30,10 @@
#define TUNABLES_INTERNAL 1
#include "dl-tunables.h"
-/* Compare environment names, bounded by the name hardcoded in glibc. */
+#define GLIBC_TUNABLES "GLIBC_TUNABLES"
+
+/* Compare environment or tunable names, bounded by the name hardcoded in
+ glibc. */
static bool
is_name (const char *orig, const char *envname)
{
@@ -45,6 +48,29 @@ is_name (const char *orig, const char *envname)
return false;
}
+static char *
+tunables_strdup (const char *in)
+{
+ size_t i = 0;
+
+ while (in[i++] != '\0');
+ char *out = __sbrk (i);
+
+ /* FIXME: In reality if the allocation fails, __sbrk will crash attempting to
+ set the thread-local errno since the TCB has not yet been set up. This
+ needs to be fixed with an __sbrk implementation that does not set
+ errno. */
+ if (out == (void *)-1)
+ return NULL;
+
+ i--;
+
+ while (i-- > 0)
+ out[i] = in[i];
+
+ return out;
+}
+
static char **
get_next_env (char **envp, char **name, size_t *namelen, char **val)
{
@@ -218,6 +244,82 @@ tunable_initialize (tunable_t *cur, const char *strval)
}
}
+static void
+parse_tunables (char *tunestr)
+{
+ if (tunestr == NULL || *tunestr == '\0')
+ return;
+
+ char *p = tunestr;
+
+ while (true)
+ {
+ char *name = p;
+ size_t len = 0;
+
+ /* First, find where the name ends. */
+ while (p[len] != '=' && p[len] != ':' && p[len] != '\0')
+ len++;
+
+ /* If we reach the end of the string before getting a valid name-value
+ pair, bail out. */
+ if (p[len] == '\0')
+ return;
+
+ /* We did not find a valid name-value pair before encountering the
+ colon. */
+ if (p[len]== ':')
+ {
+ p += len + 1;
+ continue;
+ }
+
+ p += len + 1;
+
+ char *value = p;
+ len = 0;
+
+ while (p[len] != ':' && p[len] != '\0')
+ len++;
+
+ char end = p[len];
+ p[len] = '\0';
+
+ /* Add the tunable if it exists. */
+ for (size_t i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
+ {
+ tunable_t *cur = &tunable_list[i];
+
+ /* If we are in a secure context (AT_SECURE) then ignore the tunable
+ unless it is explicitly marked as secure. Tunable values take
+ precendence over their envvar aliases. */
+ if (__libc_enable_secure && !cur->is_secure)
+ continue;
+
+ if (is_name (cur->name, name))
+ {
+ tunable_initialize (cur, value);
+ break;
+ }
+ }
+
+ if (end == ':')
+ p += len + 1;
+ else
+ return;
+ }
+}
+
+static size_t
+min_strlen (const char *s)
+{
+ size_t i = 0;
+ while (*s++ != '\0')
+ i++;
+
+ return i;
+}
+
/* Disable a tunable if it is set. */
static void
disable_tunable (tunable_id_t id, char **envp)
@@ -226,6 +328,23 @@ disable_tunable (tunable_id_t id, char **envp)
if (env_alias != NULL)
tunables_unsetenv (envp, tunable_list[id].env_alias);
+
+ char *tunable = getenv (GLIBC_TUNABLES);
+ const char *cmp = tunable_list[id].name;
+ const size_t len = min_strlen (cmp);
+
+ while (tunable && *tunable != '\0' && *tunable != ':')
+ {
+ if (is_name (tunable, cmp))
+ {
+ tunable += len;
+ /* Overwrite the = and the value with colons. */
+ while (*tunable != '\0' && *tunable != ':')
+ *tunable++ = ':';
+ break;
+ }
+ tunable++;
+ }
}
/* Disable the glibc.malloc.check tunable in SETUID/SETGID programs unless
@@ -256,6 +375,14 @@ __tunables_init (char **envp)
while ((envp = get_next_env (envp, &envname, &len, &envval)) != NULL)
{
+ if (is_name (GLIBC_TUNABLES, envname))
+ {
+ char *val = tunables_strdup (envval);
+ if (val != NULL)
+ parse_tunables (val);
+ continue;
+ }
+
for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
{
tunable_t *cur = &tunable_list[i];