[musl] [PATCH] modify dladdr to add dladdr1 support

[Jules Maselbas <jmaselbas@zdiv.net>]

The dladdr1() function is very much like dladdr(), but also returns
additional information depending on the value of the flags argument,
which can be one of the following values:

 - RTLD_DL_LINKMAP, returns a pointer to the link map for the matched
   file, same as dlinfo() with the RTLD_DI_LINKMAP request.

 - RTLD_DL_SYMENT, returns a pointer to the ELF symbole structure that
   matched for the given addr argument.

---
Implemented this because it is used by plthook (a dependency of renderdoc),
I have not tested this.

 include/dlfcn.h    |  3 +++
 ldso/dynlink.c     | 12 +++++++++++-
 src/ldso/dladdr1.c |  9 +++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 src/ldso/dladdr1.c

diff --git a/include/dlfcn.h b/include/dlfcn.h
index 13ab71dd..8d09767a 100644
--- a/include/dlfcn.h
+++ b/include/dlfcn.h
@@ -32,6 +32,9 @@ typedef struct {
 	void *dli_saddr;
 } Dl_info;
 int dladdr(const void *, Dl_info *);
+int dladdr1(const void *, Dl_info *, void **, int);
+#define RTLD_DL_SYMENT  1
+#define RTLD_DL_LINKMAP 2
 int dlinfo(void *, int, void *);
 #endif
 
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 324aa859..5cc550d6 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -2291,7 +2291,7 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra)
 	return laddr(def.dso, def.sym->st_value);
 }
 
-int dladdr(const void *addr_arg, Dl_info *info)
+int dladdr1(const void *addr_arg, Dl_info *info, void **extra_info, int flags)
 {
 	size_t addr = (size_t)addr_arg;
 	struct dso *p;
@@ -2355,9 +2355,19 @@ int dladdr(const void *addr_arg, Dl_info *info)
 	info->dli_sname = strings + bestsym->st_name;
 	info->dli_saddr = (void *)best;
 
+	if (flags == RTLD_DL_LINKMAP)
+		*(struct link_map **)extra_info = (void *)p;
+	if (flags == RTLD_DL_SYMENT)
+		*(const Sym **)extra_info = bestsym;
+
 	return 1;
 }
 
+int dladdr(const void *addr_arg, Dl_info *info)
+{
+	return dladdr1(addr_arg, info, NULL, 0);
+}
+
 hidden void *__dlsym(void *restrict p, const char *restrict s, void *restrict ra)
 {
 	void *res;
diff --git a/src/ldso/dladdr1.c b/src/ldso/dladdr1.c
new file mode 100644
index 00000000..b1e51379
--- /dev/null
+++ b/src/ldso/dladdr1.c
@@ -0,0 +1,9 @@
+#define _GNU_SOURCE
+#include <dlfcn.h>
+
+static int stub_dladdr1(const void *addr, Dl_info *info, void **extra_info, int flags)
+{
+	return 0;
+}
+
+weak_alias(stub_dladdr1, dladdr1);
-- 
2.43.0