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[PATCH 4/6] Initialize tunable list with the GLIBC_TUNABLES environment variable
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: libc-alpha at sourceware dot org
- Date: Mon, 24 Oct 2016 20:12:46 +0530
- Subject: [PATCH 4/6] Initialize tunable list with the GLIBC_TUNABLES environment variable
- Authentication-results: sourceware.org; auth=none
- References: <1477320168-23397-1-git-send-email-siddhesh@sourceware.org>
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
* elf/dl-tunables.c: Include mman.h and libc-internals.h.
(GLIBC_TUNABLES): New macro.
(tunables_strdup): New function.
(parse_tunables): 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.
---
elf/dl-tunables.c | 115 +++++++++++++++++++++++++++++
malloc/Makefile | 6 +-
malloc/tst-malloc-usable-static-tunables.c | 1 +
malloc/tst-malloc-usable-tunables.c | 1 +
4 files changed, 122 insertions(+), 1 deletion(-)
create mode 100644 malloc/tst-malloc-usable-static-tunables.c
create mode 100644 malloc/tst-malloc-usable-tunables.c
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 91340b6..6612885 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -22,6 +22,7 @@
#include <stdbool.h>
#include <unistd.h>
#include <stdlib.h>
+#include <sys/mman.h>
#include <libc-internal.h>
#include <sysdep.h>
#include <fcntl.h>
@@ -29,6 +30,8 @@
#define TUNABLES_INTERNAL 1
#include "dl-tunables.h"
+#define GLIBC_TUNABLES "GLIBC_TUNABLES"
+
/* Compare environment names, bounded by the name hardcoded in glibc. */
static bool
is_name (const char *orig, const char *envname)
@@ -44,6 +47,27 @@ is_name (const char *orig, const char *envname)
return false;
}
+static char *tunables_strdup (const char *in)
+{
+ size_t i = 0;
+
+ while (in[i++]);
+
+ char *out = __mmap (NULL, ALIGN_UP (i, __getpagesize ()),
+ PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1,
+ 0);
+
+ if (out == MAP_FAILED)
+ 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)
{
@@ -208,6 +232,72 @@ 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;
+ }
+}
+
/* Disable a tunable if it is set. */
static void
disable_tunable (tunable_id_t id, char **envp)
@@ -216,6 +306,23 @@ disable_tunable (tunable_id_t id, char **envp)
if (env_alias)
tunables_unsetenv (envp, tunable_list[id].env_alias);
+
+ char *tunable = getenv (GLIBC_TUNABLES);
+ const char *cmp = tunable_list[id].name;
+ const size_t len = strlen (cmp);
+
+ while (tunable && *tunable != '\0' && *tunable != ':')
+ {
+ if (strncmp (tunable, cmp, len) == 0)
+ {
+ 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
@@ -246,6 +353,14 @@ __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];
diff --git a/malloc/Makefile b/malloc/Makefile
index e7c2cb7..4e4898c 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -33,11 +33,13 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-mallocfork2 \
tst-interpose-nothread \
tst-interpose-thread \
+ tst-malloc-usable-tunables
tests-static := \
tst-interpose-static-nothread \
tst-interpose-static-thread \
- tst-malloc-usable-static
+ tst-malloc-usable-static \
+ tst-malloc-usable-static-tunables
tests += $(tests-static)
test-srcs = tst-mtrace
@@ -157,6 +159,8 @@ endif
tst-mcheck-ENV = MALLOC_CHECK_=3
tst-malloc-usable-ENV = MALLOC_CHECK_=3
tst-malloc-usable-static-ENV = $(tst-malloc-usable-ENV)
+tst-malloc-usable-tunables-ENV = GLIBC_TUNABLES=glibc.malloc.check=3
+tst-malloc-usable-static-tunables-ENV = $(tst-malloc-usable-tunables-ENV)
# Uncomment this for test releases. For public releases it is too expensive.
#CPPFLAGS-malloc.o += -DMALLOC_DEBUG=1
diff --git a/malloc/tst-malloc-usable-static-tunables.c b/malloc/tst-malloc-usable-static-tunables.c
new file mode 100644
index 0000000..8907db0
--- /dev/null
+++ b/malloc/tst-malloc-usable-static-tunables.c
@@ -0,0 +1 @@
+#include <malloc/tst-malloc-usable.c>
diff --git a/malloc/tst-malloc-usable-tunables.c b/malloc/tst-malloc-usable-tunables.c
new file mode 100644
index 0000000..8907db0
--- /dev/null
+++ b/malloc/tst-malloc-usable-tunables.c
@@ -0,0 +1 @@
+#include <malloc/tst-malloc-usable.c>
--
2.7.4