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| author | Florian Weimer <fweimer@redhat.com> | 2021-02-25 12:10:57 +0100 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2021-02-25 12:13:02 +0100 |
| commit | 035c012e32c11e84d64905efaf55e74f704d3668 (patch) | |
| tree | 7b08a9e9cbd8e4dd2e420cd6b7c204aeb5d61ccc /sysdeps/aarch64 | |
| parent | a79328c745219dcb395070cdcd3be065a8347f24 (diff) | |
| download | glibc-035c012e32c11e84d64905efaf55e74f704d3668.tar.gz glibc-035c012e32c11e84d64905efaf55e74f704d3668.tar.xz glibc-035c012e32c11e84d64905efaf55e74f704d3668.zip | |
Reduce the statically linked startup code [BZ #23323]
It turns out the startup code in csu/elf-init.c has a perfect pair of ROP gadgets (see Marco-Gisbert and Ripoll-Ripoll, "return-to-csu: A New Method to Bypass 64-bit Linux ASLR"). These functions are not needed in dynamically-linked binaries because DT_INIT/DT_INIT_ARRAY are already processed by the dynamic linker. However, the dynamic linker skipped the main program for some reason. For maximum backwards compatibility, this is not changed, and instead, the main map is consulted from __libc_start_main if the init function argument is a NULL pointer. For statically linked binaries, the old approach based on linker symbols is still used because there is nothing else available. A new symbol version __libc_start_main@@GLIBC_2.34 is introduced because new binaries running on an old libc would not run their ELF constructors, leading to difficult-to-debug issues.
Diffstat (limited to 'sysdeps/aarch64')
| -rw-r--r-- | sysdeps/aarch64/start.S | 14 |
1 files changed, 2 insertions, 12 deletions
diff --git a/sysdeps/aarch64/start.S b/sysdeps/aarch64/start.S index 3761cbd7ee..417da8802b 100644 --- a/sysdeps/aarch64/start.S +++ b/sysdeps/aarch64/start.S @@ -63,26 +63,16 @@ ENTRY(_start) # ifdef SHARED adrp x0, :got:main ldr PTR_REG (0), [x0, #:got_lo12:main] - - adrp x3, :got:__libc_csu_init - ldr PTR_REG (3), [x3, #:got_lo12:__libc_csu_init] - - adrp x4, :got:__libc_csu_fini - ldr PTR_REG (4), [x4, #:got_lo12:__libc_csu_fini] # else adrp x0, __wrap_main add x0, x0, :lo12:__wrap_main - adrp x3, __libc_csu_init - add x3, x3, :lo12:__libc_csu_init - adrp x4, __libc_csu_fini - add x4, x4, :lo12:__libc_csu_fini # endif #else /* Set up the other arguments in registers */ MOVL (0, main) - MOVL (3, __libc_csu_init) - MOVL (4, __libc_csu_fini) #endif + mov x3, #0 /* Used to be init. */ + mov x4, #0 /* Used to be fini. */ /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */ |