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Use __ehdr_start rather than _begin in _dl_start_final

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__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>
This commit is contained in:
Alan Modra 2022-04-27 14:39:10 +09:30
parent 911c63a51c
commit 6f043e0ee7
2 changed files with 4 additions and 6 deletions
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3
elf/Makefile
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@ -1336,8 +1336,7 @@ $(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 }'

7
elf/rtld.c
View File

@ -440,8 +440,8 @@ 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;
@ -490,7 +490,7 @@ _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. */
@ -1741,7 +1741,6 @@ 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. */