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* [glibc/release/2.35/master] Use __ehdr_start rather than _begin in _dl_start_final
@ 2022-09-15 6:04 Aurelien Jarno
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From: Aurelien Jarno @ 2022-09-15 6:04 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=55a636430bd382fb9537e6d33cc6bc57bc2660c1
commit 55a636430bd382fb9537e6d33cc6bc57bc2660c1
Author: Alan Modra <amodra@gmail.com>
Date: Wed Apr 27 14:39:10 2022 +0930
Use __ehdr_start rather than _begin in _dl_start_final
__ehdr_start is already used in rltld.c:dl_main, and can serve the
same purpose as _begin. Besides tidying the code, using linker
defined section relative symbols rather than "-defsym _begin=0" better
reflects the intent of _dl_start_final use of _begin, which is to
refer to the load address of ld.so rather than absolute address zero.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit 6f043e0ee7e477f50a44024ed0cb579d5e3f511d)
Diff:
---
elf/Makefile | 3 +--
elf/rtld.c | 7 +++----
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/elf/Makefile b/elf/Makefile
index 811859654a..bf2550472b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1296,8 +1296,7 @@ $(objpfx)ld.so: $(objpfx)librtld.os $(ld-map)
$(LINK.o) -nostdlib -nostartfiles -shared -o $@.new \
$(LDFLAGS-rtld) -Wl,-z,defs $(z-now-$(bind-now)) \
$(filter-out $(map-file),$^) $(load-map-file) \
- -Wl,-soname=$(rtld-installed-name) \
- -Wl,-defsym=_begin=0
+ -Wl,-soname=$(rtld-installed-name)
$(call after-link,$@.new)
$(READELF) -s $@.new \
| $(AWK) '($$7 ~ /^UND(|EF)$$/ && $$1 != "0:" && $$4 != "REGISTER") { print; p=1 } END { exit p != 0 }'
diff --git a/elf/rtld.c b/elf/rtld.c
index 9cc9e5fd4c..86354fb0c2 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -441,8 +441,8 @@ static ElfW(Addr) _dl_start_final (void *arg,
struct dl_start_final_info *info);
#endif
-/* These defined magically in the linker script. */
-extern char _begin[] attribute_hidden;
+/* These are defined magically by the linker. */
+extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
extern char _etext[] attribute_hidden;
extern char _end[] attribute_hidden;
@@ -487,7 +487,7 @@ _dl_start_final (void *arg, struct dl_start_final_info *info)
#endif
_dl_setup_hash (&GL(dl_rtld_map));
GL(dl_rtld_map).l_real = &GL(dl_rtld_map);
- GL(dl_rtld_map).l_map_start = (ElfW(Addr)) _begin;
+ GL(dl_rtld_map).l_map_start = (ElfW(Addr)) &__ehdr_start;
GL(dl_rtld_map).l_map_end = (ElfW(Addr)) _end;
GL(dl_rtld_map).l_text_end = (ElfW(Addr)) _etext;
/* Copy the TLS related data if necessary. */
@@ -1801,7 +1801,6 @@ dl_main (const ElfW(Phdr) *phdr,
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. */
- extern const ElfW(Ehdr) __ehdr_start __attribute__ ((visibility ("hidden")));
/* Set up the program header information for the dynamic linker
itself. It is needed in the dl_iterate_phdr callbacks. */
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