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authorJohn Högberg <[email protected]>2017-11-22 13:19:57 +0100
committerJohn Högberg <[email protected]>2018-01-03 08:14:28 +0100
commitc2d70945dce9cb09d5d7120d6e9ddf7faac8d230 (patch)
tree3cfbaca9af7b6a32871e669a39027ce987c846da /erts/emulator/sys/unix/sys_env.c
parentbe9f93b14e0fb9ff09db36abde62ae8099bf5bd0 (diff)
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Replace the libc environment with a thread-safe emulation
putenv(3) and friends aren't thread-safe regardless of how you slice it; a global lock around all environment operations (like before) keeps things safe as far as our own operations go, but we have absolutely no control over what libc or a library dragged in by a driver/NIF does -- they're free to call getenv(3) or putenv(3) without honoring our lock. This commit solves this by setting up an "emulated" environment which can't be touched without going through our interfaces. Third-party libraries can still shoot themselves in the foot but benign uses of os:putenv/2 will no longer risk crashing the emulator.
Diffstat (limited to 'erts/emulator/sys/unix/sys_env.c')
-rw-r--r--erts/emulator/sys/unix/sys_env.c133
1 files changed, 133 insertions, 0 deletions
diff --git a/erts/emulator/sys/unix/sys_env.c b/erts/emulator/sys/unix/sys_env.c
new file mode 100644
index 0000000000..4d8301f985
--- /dev/null
+++ b/erts/emulator/sys/unix/sys_env.c
@@ -0,0 +1,133 @@
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "sys.h"
+#include "erl_osenv.h"
+#include "erl_alloc.h"
+
+#include "erl_thr_progress.h"
+
+static erts_osenv_t sysenv_global_env;
+static erts_rwmtx_t sysenv_rwmtx;
+
+extern char **environ;
+
+static void import_initial_env(void);
+
+void erts_sys_env_init() {
+ erts_rwmtx_init(&sysenv_rwmtx, "environ", NIL,
+ ERTS_LOCK_FLAGS_PROPERTY_STATIC | ERTS_LOCK_FLAGS_CATEGORY_GENERIC);
+
+ erts_osenv_init(&sysenv_global_env);
+ import_initial_env();
+}
+
+const erts_osenv_t *erts_sys_rlock_global_osenv() {
+ erts_rwmtx_rlock(&sysenv_rwmtx);
+ return &sysenv_global_env;
+}
+
+erts_osenv_t *erts_sys_rwlock_global_osenv() {
+ erts_rwmtx_rwlock(&sysenv_rwmtx);
+ return &sysenv_global_env;
+}
+
+void erts_sys_rwunlock_global_osenv() {
+ erts_rwmtx_rwunlock(&sysenv_rwmtx);
+}
+
+void erts_sys_runlock_global_osenv() {
+ erts_rwmtx_runlock(&sysenv_rwmtx);
+}
+
+int erts_sys_explicit_8bit_putenv(char *key, char *value) {
+ erts_osenv_data_t env_key, env_value;
+ int result;
+
+ env_key.length = sys_strlen(key);
+ env_key.data = key;
+
+ env_value.length = sys_strlen(value);
+ env_value.data = value;
+
+ {
+ erts_osenv_t *env = erts_sys_rwlock_global_osenv();
+ result = erts_osenv_put_native(env, &env_key, &env_value);
+ erts_sys_rwunlock_global_osenv();
+ }
+
+ return result;
+}
+
+int erts_sys_explicit_8bit_getenv(char *key, char *value, size_t *size) {
+ erts_osenv_data_t env_key, env_value;
+ int result;
+
+ env_key.length = sys_strlen(key);
+ env_key.data = key;
+
+ /* Reserve space for NUL termination. */
+ env_value.length = *size - 1;
+ env_value.data = value;
+
+ {
+ const erts_osenv_t *env = erts_sys_rlock_global_osenv();
+ result = erts_osenv_get_native(env, &env_key, &env_value);
+ erts_sys_runlock_global_osenv();
+ }
+
+ if(result == 1) {
+ value[env_value.length] = '\0';
+ }
+
+ *size = env_value.length;
+
+ return result;
+}
+
+int erts_sys_explicit_host_getenv(char *key, char *value, size_t *size) {
+ char *orig_value;
+ size_t length;
+
+ orig_value = getenv(key);
+
+ if(orig_value == NULL) {
+ return 0;
+ }
+
+ length = sys_strlen(orig_value);
+
+ if (length >= *size) {
+ *size = length + 1;
+ return -1;
+ }
+
+ sys_memcpy((void*)value, (void*)orig_value, length + 1);
+ *size = length;
+
+ return 1;
+}
+
+static void import_initial_env(void) {
+ char **environ_iterator, *environ_variable;
+
+ environ_iterator = environ;
+
+ while ((environ_variable = *(environ_iterator++)) != NULL) {
+ char *separator_index = strchr(environ_variable, '=');
+
+ if (separator_index != NULL) {
+ erts_osenv_data_t env_key, env_value;
+
+ env_key.length = separator_index - environ_variable;
+ env_key.data = environ_variable;
+
+ env_value.length = sys_strlen(separator_index) - 1;
+ env_value.data = separator_index + 1;
+
+ erts_osenv_put_native(&sysenv_global_env, &env_key, &env_value);
+ }
+ }
+}