add dl_iterate_phdr interface

patches by Alex Caudill (npx). the dynamic-linked version is almost
identical to the final submitted patch; I just added a couple missing
lines for saving the phdr address when the dynamic linker is invoked
directly to run a program, and removed a couple to avoid introducing
another unnecessary type. the static-linked version is based on npx's
draft. it could use some improvements which are contingent on the
startup code saving some additional information for later use.

1 files changed, 27 insertions, 0 deletions

diff --git a/include/link.h b/include/link.h
new file mode 100644
index 00000000..d5160e7e
--- /dev/null
+++ b/include/link.h
@@ -0,0 +1,27 @@
+#ifndef _LINK_H
+#define _LINK_H
+
+#include <elf.h>
+#define __NEED_size_t
+#include <bits/alltypes.h>
+
+#if UINTPTR_MAX > 0xffffffff
+#define ElfW(type) Elf64_ ## type
+#else
+#define ElfW(type) Elf32_ ## type
+#endif
+
+struct dl_phdr_info {
+	ElfW(Addr) dlpi_addr;
+	const char *dlpi_name;
+	const ElfW(Phdr) *dlpi_phdr;
+	ElfW(Half) dlpi_phnum;
+	unsigned long long int dlpi_adds;
+	unsigned long long int dlpi_subs;
+	size_t dlpi_tls_modid;
+	void *dlpi_tls_data;
+};
+
+int dl_iterate_phdr(int (*)(struct dl_phdr_info *, size_t, void *), void *);
+
+#endif