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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/sparc | |
| 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/sparc')
| -rw-r--r-- | sysdeps/sparc/sparc32/start.S | 12 | ||||
| -rw-r--r-- | sysdeps/sparc/sparc64/start.S | 12 |
2 files changed, 4 insertions, 20 deletions
diff --git a/sysdeps/sparc/sparc32/start.S b/sysdeps/sparc/sparc32/start.S index 45ca77da3e..00bf898fb9 100644 --- a/sysdeps/sparc/sparc32/start.S +++ b/sysdeps/sparc/sparc32/start.S @@ -59,22 +59,14 @@ _start: /* Load the addresses of the user entry points. */ #ifndef PIC sethi %hi(main), %o0 - sethi %hi(__libc_csu_init), %o3 - sethi %hi(__libc_csu_fini), %o4 or %o0, %lo(main), %o0 - or %o3, %lo(__libc_csu_init), %o3 - or %o4, %lo(__libc_csu_fini), %o4 #else sethi %gdop_hix22(main), %o0 - sethi %gdop_hix22(__libc_csu_init), %o3 - sethi %gdop_hix22(__libc_csu_fini), %o4 xor %o0, %gdop_lox10(main), %o0 - xor %o3, %gdop_lox10(__libc_csu_init), %o3 - xor %o4, %gdop_lox10(__libc_csu_fini), %o4 ld [%l7 + %o0], %o0, %gdop(main) - ld [%l7 + %o3], %o3, %gdop(__libc_csu_init) - ld [%l7 + %o4], %o4, %gdop(__libc_csu_fini) #endif + mov 0, %o3 /* Used to be init. */ + mov 0, %o4 /* Used to be fini. */ /* When starting a binary via the dynamic linker, %g1 contains the address of the shared library termination function, which will be diff --git a/sysdeps/sparc/sparc64/start.S b/sysdeps/sparc/sparc64/start.S index 210fbaff90..8520717eba 100644 --- a/sysdeps/sparc/sparc64/start.S +++ b/sysdeps/sparc/sparc64/start.S @@ -60,22 +60,14 @@ _start: /* Load the addresses of the user entry points. */ #ifndef PIC sethi %hi(main), %o0 - sethi %hi(__libc_csu_init), %o3 - sethi %hi(__libc_csu_fini), %o4 or %o0, %lo(main), %o0 - or %o3, %lo(__libc_csu_init), %o3 - or %o4, %lo(__libc_csu_fini), %o4 #else sethi %gdop_hix22(main), %o0 - sethi %gdop_hix22(__libc_csu_init), %o3 - sethi %gdop_hix22(__libc_csu_fini), %o4 xor %o0, %gdop_lox10(main), %o0 - xor %o3, %gdop_lox10(__libc_csu_init), %o3 - xor %o4, %gdop_lox10(__libc_csu_fini), %o4 ldx [%l7 + %o0], %o0, %gdop(main) - ldx [%l7 + %o3], %o3, %gdop(__libc_csu_init) - ldx [%l7 + %o4], %o4, %gdop(__libc_csu_fini) #endif + mov 0, %o3 /* Used to be init. */ + mov 0, %o4 /* Used to be fini. */ /* When starting a binary via the dynamic linker, %g1 contains the address of the shared library termination function, which will be |