From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 1 Aug 2025 17:27:04 +0000 (+0200)
Subject: elf: Extract rtld_setup_phdr function from dl_main
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2fadee530155bae6682ab2965d6ff3a2fc9eced6;p=thirdparty%2Fglibc.git

elf: Extract rtld_setup_phdr function from dl_main

Remove historic binutils reference from comment and update
how this data is used by applications.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
(cherry picked from commit 2cac9559e06044ba520e785c151fbbd25011865f)
---

diff --git a/elf/rtld.c b/elf/rtld.c
index 493f9696ea..6fb900fb31 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1239,6 +1239,37 @@ rtld_setup_main_map (struct link_map *main_map)
   return has_interp;
 }
 
+/* Set up the program header information for the dynamic linker
+   itself.  It can be accessed via _r_debug and dl_iterate_phdr
+   callbacks.  */
+static void
+rtld_setup_phdr (void)
+{
+  /* Starting from binutils-2.23, the linker will define the magic
+     symbol __ehdr_start to point to our own ELF header if it is
+     visible in a segment that also includes the phdrs.  */
+
+  const ElfW(Ehdr) *rtld_ehdr = &__ehdr_start;
+  assert (rtld_ehdr->e_ehsize == sizeof *rtld_ehdr);
+  assert (rtld_ehdr->e_phentsize == sizeof (ElfW(Phdr)));
+
+  const ElfW(Phdr) *rtld_phdr = (const void *) rtld_ehdr + rtld_ehdr->e_phoff;
+
+  _dl_rtld_map.l_phdr = rtld_phdr;
+  _dl_rtld_map.l_phnum = rtld_ehdr->e_phnum;
+
+
+  /* PT_GNU_RELRO is usually the last phdr.  */
+  size_t cnt = rtld_ehdr->e_phnum;
+  while (cnt-- > 0)
+    if (rtld_phdr[cnt].p_type == PT_GNU_RELRO)
+      {
+	_dl_rtld_map.l_relro_addr = rtld_phdr[cnt].p_vaddr;
+	_dl_rtld_map.l_relro_size = rtld_phdr[cnt].p_memsz;
+	break;
+      }
+}
+
 /* Adjusts the contents of the stack and related globals for the user
    entry point.  The ld.so processed skip_args arguments and bumped
    _dl_argv and _dl_argc accordingly.  Those arguments are removed from
@@ -1705,33 +1736,7 @@ dl_main (const ElfW(Phdr) *phdr,
   ++GL(dl_ns)[LM_ID_BASE]._ns_nloaded;
   ++GL(dl_load_adds);
 
-  /* Starting from binutils-2.23, the linker will define the magic symbol
-     __ehdr_start to point to our own ELF header if it is visible in a
-     segment that also includes the phdrs.  If that's not available, we use
-     the old method that assumes the beginning of the file is part of the
-     lowest-addressed PT_LOAD segment.  */
-
-  /* Set up the program header information for the dynamic linker
-     itself.  It is needed in the dl_iterate_phdr callbacks.  */
-  const ElfW(Ehdr) *rtld_ehdr = &__ehdr_start;
-  assert (rtld_ehdr->e_ehsize == sizeof *rtld_ehdr);
-  assert (rtld_ehdr->e_phentsize == sizeof (ElfW(Phdr)));
-
-  const ElfW(Phdr) *rtld_phdr = (const void *) rtld_ehdr + rtld_ehdr->e_phoff;
-
-  _dl_rtld_map.l_phdr = rtld_phdr;
-  _dl_rtld_map.l_phnum = rtld_ehdr->e_phnum;
-
-
-  /* PT_GNU_RELRO is usually the last phdr.  */
-  size_t cnt = rtld_ehdr->e_phnum;
-  while (cnt-- > 0)
-    if (rtld_phdr[cnt].p_type == PT_GNU_RELRO)
-      {
-	_dl_rtld_map.l_relro_addr = rtld_phdr[cnt].p_vaddr;
-	_dl_rtld_map.l_relro_size = rtld_phdr[cnt].p_memsz;
-	break;
-      }
+  rtld_setup_phdr ();
 
   /* Add the dynamic linker to the TLS list if it also uses TLS.  */
   if (_dl_rtld_map.l_tls_blocksize != 0)