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diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc
--- a/lib/libc/gen/Makefile.inc
+++ b/lib/libc/gen/Makefile.inc
@@ -275,6 +275,7 @@
raise.3 \
rand48.3 \
readpassphrase.3 \
+ rtld_get_effective_env_var.3 \
scandir.3 \
sem_destroy.3 \
sem_getvalue.3 \
@@ -481,6 +482,8 @@
rand48.3 nrand48.3 \
rand48.3 seed48.3 \
rand48.3 srand48.3
+MLINKS+=rtld_get_effective_env_var.3 \
+ rtld_set_effective_env_var.3
MLINKS+=scandir.3 alphasort.3 \
scandir.3 scandirat.3 \
scandir.3 scandir_b.3 \
diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map
--- a/lib/libc/gen/Symbol.map
+++ b/lib/libc/gen/Symbol.map
@@ -456,6 +456,8 @@
aio_read2;
aio_write2;
execvpe;
+ rtld_get_effective_env_var;
+ rtld_set_effective_env_var;
};
FBSDprivate_1.0 {
diff --git a/lib/libc/gen/dlfcn.c b/lib/libc/gen/dlfcn.c
--- a/lib/libc/gen/dlfcn.c
+++ b/lib/libc/gen/dlfcn.c
@@ -35,6 +35,7 @@
#include <sys/mman.h>
#include <machine/atomic.h>
#include <dlfcn.h>
+#include <errno.h>
#include <link.h>
#include <stddef.h>
#include <string.h>
@@ -337,4 +338,20 @@
return (0);
}
+#pragma weak rtld_get_effective_env_var
+const char *
+rtld_get_effective_env_var(const char *name __unused)
+{
+ _rtld_error(sorry);
+ return (NULL);
+}
+
+#pragma weak rtld_set_effective_env_var
+int
+rtld_set_effective_env_var(const char *name __unused, const char *val __unused)
+{
+ _rtld_error(sorry);
+ return (EINVAL);
+}
+
#endif /* !defined(IN_LIBDL) || defined(PIC) */
diff --git a/lib/libc/gen/rtld_get_effective_env_var.3 b/lib/libc/gen/rtld_get_effective_env_var.3
new file mode 100644
--- /dev/null
+++ b/lib/libc/gen/rtld_get_effective_env_var.3
@@ -0,0 +1,106 @@
+.\" Copyright (c) 2024 The FreeBSD Foundation
+.\"
+.\" This documentation was written by
+.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
+.\" from the FreeBSD Foundation.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd October 31, 2024
+.Dt RTLD_GET_EFFECTIVE_ENV_VAR 3
+.Os
+.Sh NAME
+.Nm rtld_get_effective_env_var ,
+.Nm rtld_set_effective_env_var
+.Nd query or change run-time linker parameters after image activation
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In sys/errno.h
+.In link.h
+.Ft const char *
+.Fn rtld_get_effective_env_var "const char *name"
+.Ft int
+.Fn rtld_set_effective_env_var "const char *name" "const char *value"
+.Sh DESCRIPTION
+The dynamic linker
+.Xr rtld 1
+can be configured be setting some environment variables for the process,
+before image activation.
+Sometimes it is desirable to query the current effective settings or
+change them afterward.
+.Pp
+Since the process environment variables are maintained by higher-level
+libraries, the run-time linker cannot access them after the image
+activation.
+The described functions make it possible to operate on rtld settings.
+.Pp
+The
+.Fn rtld_get_effective_env_var
+function returns the current value of the named parameter.
+.Pp
+The
+.Fn rtld_set_effective_env_var
+functions changes the value of the parameter to the new
+.Fa value
+value, if possible.
+The
+.Fa name
+argument to both functions is the name of the parameter, which
+is same as the corresponding environment variable
+.Pq see Xr rtld 1
+but without the
+.Ev LD_
+(or
+.Ev LD_32_
+or any other ABI-specific) prefix.
+.Sh RETURN VALUES
+The
+.Fn rtld_get_effective_env_var
+returns the current value of the named parameter, or
+.Dv NULL
+if the name is invalid.
+.Pp
+The
+.Fn rtld_set_effective_env_var
+returns 0 on success, or an integer indicating the error condition
+which prevented the operation.
+.Sh ERRORS
+Possible errors returned from
+.Fn rtld_set_effective_env_var :
+.Bl -tag -width Er
+.It Bq Er EPERM
+The requested change cannot be made at runtime, either because the
+runtime linker can only take this parameter at initialization time,
+or because the current process is executing with elevated privileges.
+.It Bq ENOENT
+The supplied parameter
+.Fa name
+is unknown.
+.El
+.Sh SEE ALSO
+.Xr rtld 1
+.Sh HISTORY
+The
+.Nm
+function first appeared in
+.Fx 15.0 .
diff --git a/lib/libdl/Symbol.map b/lib/libdl/Symbol.map
--- a/lib/libdl/Symbol.map
+++ b/lib/libdl/Symbol.map
@@ -17,3 +17,8 @@
FBSD_1.3 {
fdlopen;
};
+
+FBSD_1.8 {
+ rtld_get_effective_env_var;
+ rtld_set_effective_env_var;
+};
diff --git a/libexec/rtld-elf/Symbol.map b/libexec/rtld-elf/Symbol.map
--- a/libexec/rtld-elf/Symbol.map
+++ b/libexec/rtld-elf/Symbol.map
@@ -21,6 +21,11 @@
fdlopen;
};
+FBSD_1.8 {
+ rtld_get_effective_env_var;
+ rtld_set_effective_env_var;
+};
+
FBSDprivate_1.0 {
_rtld_thread_init;
_rtld_allocate_tls;
diff --git a/libexec/rtld-elf/rtld.1 b/libexec/rtld-elf/rtld.1
--- a/libexec/rtld-elf/rtld.1
+++ b/libexec/rtld-elf/rtld.1
@@ -138,6 +138,10 @@
for example:
.Ev LD_32_TRACE_LOADED_OBJECTS .
If the activated image is setuid or setgid, the variables are ignored.
+At run-time, effective settings can be queried using
+.Xr rtld_get_effective_env_var 3 ,
+and some of them can be changed with
+.Xr rtld_set_effective_env_var 3 .
.Bl -tag -width ".Ev LD_LIBMAP_DISABLE"
.It Ev LD_DUMP_REL_POST
If set,
@@ -527,6 +531,7 @@
.Xr ld 1 ,
.Xr ldd 1 ,
.Xr dlinfo 3 ,
+.Xr rtld_get_effective_env_var 3 ,
.Xr capsicum 4 ,
.Xr elf 5 ,
.Xr libmap.conf 5 ,
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -257,6 +257,8 @@
int _rtld_get_stack_prot(void) __exported;
int _rtld_is_dlopened(void *) __exported;
void _rtld_error(const char *, ...) __exported;
+const char *rtld_get_effective_env_var(const char *name) __exported;
+int rtld_set_effective_env_var(const char *name, const char *val) __exported;
/* Only here to fix -Wmissing-prototypes warnings */
int __getosreldate(void);
@@ -346,36 +348,43 @@
struct ld_env_var_desc {
const char * const n;
const char *val;
- const bool unsecure;
+ const bool unsecure:1;
+ const bool can_update:1;
+ bool owned:1;
};
-#define LD_ENV_DESC(var, unsec) \
- [LD_##var] = { .n = #var, .unsecure = unsec }
+#define LD_ENV_DESC(var, unsec, cu) \
+ [LD_##var] = { \
+ .n = #var, \
+ .unsecure = unsec, \
+ .can_update = cu, \
+ .owned = false, \
+ }
static struct ld_env_var_desc ld_env_vars[] = {
- 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),
- LD_ENV_DESC(SHOW_AUXV, false),
- LD_ENV_DESC(STATIC_TLS_EXTRA, false),
- LD_ENV_DESC(NO_DL_ITERATE_PHDR_AFTER_FORK, false),
+ LD_ENV_DESC(BIND_NOW, false, false),
+ LD_ENV_DESC(PRELOAD, true, false),
+ LD_ENV_DESC(LIBMAP, true, false),
+ LD_ENV_DESC(LIBRARY_PATH, true, true),
+ LD_ENV_DESC(LIBRARY_PATH_FDS, true, true),
+ LD_ENV_DESC(LIBMAP_DISABLE, true, false),
+ LD_ENV_DESC(BIND_NOT, true, false),
+ LD_ENV_DESC(DEBUG, true, true),
+ LD_ENV_DESC(ELF_HINTS_PATH, true, false),
+ LD_ENV_DESC(LOADFLTR, true, false),
+ LD_ENV_DESC(LIBRARY_PATH_RPATH, true, true),
+ LD_ENV_DESC(PRELOAD_FDS, true, false),
+ LD_ENV_DESC(DYNAMIC_WEAK, true, true),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS, false, false),
+ LD_ENV_DESC(UTRACE, false, true),
+ LD_ENV_DESC(DUMP_REL_PRE, false, true),
+ LD_ENV_DESC(DUMP_REL_POST, false, true),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_PROGNAME, false, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT1, false, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT2, false, false),
+ LD_ENV_DESC(TRACE_LOADED_OBJECTS_ALL, false, false),
+ LD_ENV_DESC(SHOW_AUXV, false, false),
+ LD_ENV_DESC(STATIC_TLS_EXTRA, false, false),
+ LD_ENV_DESC(NO_DL_ITERATE_PHDR_AFTER_FORK, false, false),
};
const char *
@@ -6326,6 +6335,41 @@
}
}
+const char *
+rtld_get_effective_env_var(const char *name)
+{
+ const struct ld_env_var_desc *lvd;
+ u_int i;
+
+ for (i = 0; i < nitems(ld_env_vars); i++) {
+ lvd = &ld_env_vars[i];
+ if (strcmp(lvd->n, name) == 0)
+ return (lvd->val);
+ }
+ return (NULL);
+}
+
+int
+rtld_set_effective_env_var(const char *name, const char *val)
+{
+ struct ld_env_var_desc *lvd;
+ u_int i;
+
+ for (i = 0; i < nitems(ld_env_vars); i++) {
+ lvd = &ld_env_vars[i];
+ if (strcmp(lvd->n, name) != 0)
+ continue;
+ if (!lvd->can_update || (lvd->unsecure && !trust))
+ return (EPERM);
+ if (lvd->owned)
+ free(__DECONST(char *, lvd->val));
+ lvd->val = xstrdup(val);
+ lvd->owned = true;
+ return (0);
+ }
+ return (ENOENT);
+}
+
/*
* Overrides for libc_pic-provided functions.
*/
diff --git a/sys/sys/link_elf.h b/sys/sys/link_elf.h
--- a/sys/sys/link_elf.h
+++ b/sys/sys/link_elf.h
@@ -93,10 +93,12 @@
__BEGIN_DECLS
typedef int (*__dl_iterate_hdr_callback)(struct dl_phdr_info *, size_t, void *);
-extern int dl_iterate_phdr(__dl_iterate_hdr_callback, void *);
+int dl_iterate_phdr(__dl_iterate_hdr_callback, void *);
int _rtld_addr_phdr(const void *, struct dl_phdr_info *);
int _rtld_get_stack_prot(void);
int _rtld_is_dlopened(void *);
+const char *rtld_get_effective_env_var(const char *name);
+int rtld_set_effective_env_var(const char *name, const char *val);
#ifdef __ARM_EABI__
void * dl_unwind_find_exidx(const void *, int *);

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