The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=bfd4c875a10560aaa2f41e82114df79fde008fdb
commit bfd4c875a10560aaa2f41e82114df79fde008fdb
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-08-16 12:59:05 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2021-08-17 12:05:47 +0000
rtld: avoid use of of getenv(3) for evaluating rtld env vars (LD_XXX)
Scan through the set of environment variables during initialization and
store values in the corresponding ld_env_var_desc structure, in the
single pass at init time. This does not eliminate use of getenv(3) and
unsetenv(3) completely, but provides a foundation to do that as the next
step.
Also organize the scan in a way that makes it easier to support aliases
like LD_DEBUG vs. LD_64_DEBUG.
Suggested by: arichardson
Reviewed by: arichardson, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D31545
---
libexec/rtld-elf/rtld.c | 144 ++++++++++++++++++++++++++++--------------------
1 file changed, 83 insertions(+), 61 deletions(-)
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index 6826dde8a160..39c41fe0ed24 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -367,82 +367,105 @@ enum {
};
struct ld_env_var_desc {
- char n[64];
- bool unsecure;
+ const char *n;
+ char *val;
+ const bool unsecure;
};
+#define LD_ENV_DESC(var, unsec) \
+ [LD_##var] = { .n = #var, .unsecure = unsec }
static struct ld_env_var_desc ld_env_vars[] = {
- [LD_BIND_NOW] =
- { .n = "BIND_NOW", .unsecure = false },
- [LD_PRELOAD] =
- { .n = "PRELOAD", .unsecure = true },
- [LD_LIBMAP] =
- { .n = "LIBMAP", .unsecure = true },
- [LD_LIBRARY_PATH] =
- { .n = "LIBRARY_PATH", .unsecure = true },
- [LD_LIBRARY_PATH_FDS] =
- { .n = "LIBRARY_PATH_FDS", .unsecure = true },
- [LD_LIBMAP_DISABLE] =
- { .n = "LIBMAP_DISABLE", .unsecure = true },
- [LD_BIND_NOT] =
- { .n = "BIND_NOT", .unsecure = true },
- [LD_DEBUG] =
- { .n = "DEBUG", .unsecure = true },
- [LD_ELF_HINTS_PATH] =
- { .n = "ELF_HINTS_PATH", .unsecure = true },
- [LD_LOADFLTR] =
- { .n = "LOADFLTR", .unsecure = true },
- [LD_LIBRARY_PATH_RPATH] =
- { .n = "LIBRARY_PATH_RPATH", .unsecure = true },
- [LD_PRELOAD_FDS] =
- { .n = "PRELOAD_FDS", .unsecure = true },
- [LD_DYNAMIC_WEAK] =
- { .n = "DYNAMIC_WEAK", .unsecure = true },
- [LD_TRACE_LOADED_OBJECTS] =
- { .n = "TRACE_LOADED_OBJECTS", .unsecure = false },
- [LD_UTRACE] =
- { .n = "UTRACE", .unsecure = false },
- [LD_DUMP_REL_PRE] =
- { .n = "DUMP_REL_PRE", .unsecure = false },
- [LD_DUMP_REL_POST] =
- { .n = "DUMP_REL_POST", .unsecure = false },
- [LD_TRACE_LOADED_OBJECTS_PROGNAME] =
- { .n = "TRACE_LOADED_OBJECTS_PROGNAME", .unsecure = false},
- [LD_TRACE_LOADED_OBJECTS_FMT1] =
- { .n = "TRACE_LOADED_OBJECTS_FMT1", .unsecure = false},
- [LD_TRACE_LOADED_OBJECTS_FMT2] =
- { .n = "TRACE_LOADED_OBJECTS_FMT2", .unsecure = false},
- [LD_TRACE_LOADED_OBJECTS_ALL] =
- { .n = "TRACE_LOADED_OBJECTS_ALL", .unsecure = false},
+ LD_ENV_DESC(BIND_NOW, false),
+ LD_ENV_DESC(PRELOAD, true),
+ LD_ENV_DESC(LIBMAP, true),
+ LD_ENV_DESC(LIBRARY_PATH, true),
+ LD_ENV_DESC(LIBRARY_PATH_FDS, true),
+ LD_ENV_DESC(LIBMAP_DISABLE, true),
+ LD_ENV_DESC(BIND_NOT, true),
+ LD_ENV_DESC(DEBUG, true),
+ LD_ENV_DESC(ELF_HINTS_PATH, true),
+ LD_ENV_DESC(LOADFLTR, true),
+ LD_ENV_DESC(LIBRARY_PATH_RPATH, true),
+ LD_ENV_DESC(PRELOAD_FDS, true),
+ LD_ENV_DESC(DYNAMIC_WEAK, true),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS, false),
+ LD_ENV_DESC(UTRACE, false),
+ LD_ENV_DESC(DUMP_REL_PRE, false),
+ LD_ENV_DESC(DUMP_REL_POST, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_PROGNAME, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT1, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT2, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_ALL, false),
};
-static const char *
-ld_var(int idx)
+static char *
+ld_get_env_var(int idx)
{
- return (ld_env_vars[idx].n);
+ return (ld_env_vars[idx].val);
}
static char *
-ld_get_env_var(int idx)
+rtld_get_env_val(char **env, const char *name, size_t name_len)
{
- return (getenv(ld_var(idx)));
+ char **m, *n, *v;
+
+ for (m = env; *m != NULL; m++) {
+ n = *m;
+ v = strchr(n, '=');
+ if (v == NULL) {
+ /* corrupt environment? */
+ continue;
+ }
+ if (v - n == (ptrdiff_t)name_len &&
+ strncmp(name, n, name_len) == 0)
+ return (v + 1);
+ }
+ return (NULL);
}
static void
-rtld_init_env_vars(void)
+rtld_init_env_vars_for_prefix(char **env, const char *env_prefix)
{
struct ld_env_var_desc *lvd;
- size_t sz;
+ size_t prefix_len, nlen;
+ char **m, *n, *v;
int i;
- sz = strlen(ld_env_prefix);
- for (i = 0; i < (int)nitems(ld_env_vars); i++) {
- lvd = &ld_env_vars[i];
- memmove(lvd->n + sz, lvd->n, strlen(lvd->n) + 1);
- memcpy(lvd->n, ld_env_prefix, sz);
+ prefix_len = strlen(env_prefix);
+ for (m = env; *m != NULL; m++) {
+ n = *m;
+ if (strncmp(env_prefix, n, prefix_len) != 0) {
+ /* Not a rtld environment variable. */
+ continue;
+ }
+ n += prefix_len;
+ v = strchr(n, '=');
+ if (v == NULL) {
+ /* corrupt environment? */
+ continue;
+ }
+ for (i = 0; i < (int)nitems(ld_env_vars); i++) {
+ lvd = &ld_env_vars[i];
+ if (lvd->val != NULL) {
+ /* Saw higher-priority variable name already. */
+ continue;
+ }
+ nlen = strlen(lvd->n);
+ if (v - n == (ptrdiff_t)nlen &&
+ strncmp(lvd->n, n, nlen) == 0) {
+ lvd->val = v + 1;
+ break;
+ }
+ }
}
}
+static void
+rtld_init_env_vars(char **env)
+{
+ rtld_init_env_vars_for_prefix(env, ld_env_prefix);
+}
+
/*
* Main entry point for dynamic linking. The first argument is the
* stack pointer. The stack is expected to be laid out as described
@@ -548,7 +571,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry
**objp)
direct_exec = false;
md_abi_variant_hook(aux_info);
- rtld_init_env_vars();
+ rtld_init_env_vars(env);
fd = -1;
if (aux_info[AT_EXECFD] != NULL) {
@@ -667,12 +690,11 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry
**objp)
if (!trust) {
for (i = 0; i < (int)nitems(ld_env_vars); i++) {
lvd = &ld_env_vars[i];
- if (lvd->unsecure && unsetenv(lvd->n)) {
- _rtld_error("environment corrupt; aborting");
- rtld_die();
- }
+ if (lvd->unsecure)
+ lvd->val = NULL;
}
}
+
ld_debug = ld_get_env_var(LD_DEBUG);
if (ld_bind_now == NULL)
ld_bind_not = ld_get_env_var(LD_BIND_NOT) != NULL;
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