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author | Siddhesh Poyarekar <siddhesh@sourceware.org> | 2016-12-31 23:33:27 +0530 |
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committer | Siddhesh Poyarekar <siddhesh@sourceware.org> | 2016-12-31 23:49:24 +0530 |
commit | 9dd409a5f4a7a053cc962f8371dad0fe5cc22597 (patch) | |
tree | a205733e557ccf0b66021deff34cd6b690150f9e /elf/dl-tunables.c | |
parent | 67e58f39412ecd4467034761f3f074283c90f3c8 (diff) | |
download | glibc-9dd409a5f4a7a053cc962f8371dad0fe5cc22597.tar glibc-9dd409a5f4a7a053cc962f8371dad0fe5cc22597.tar.gz glibc-9dd409a5f4a7a053cc962f8371dad0fe5cc22597.tar.bz2 glibc-9dd409a5f4a7a053cc962f8371dad0fe5cc22597.zip |
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/dl-tunables.c')
-rw-r--r-- | elf/dl-tunables.c | 129 |
1 files changed, 128 insertions, 1 deletions
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c index 472747b3da..8d6914020d 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]; |