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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/csky | |
| parent | a79328c745219dcb395070cdcd3be065a8347f24 (diff) | |
| download | glibc-035c012e32c11e84d64905efaf55e74f704d3668.zip glibc-035c012e32c11e84d64905efaf55e74f704d3668.tar.gz glibc-035c012e32c11e84d64905efaf55e74f704d3668.tar.bz2 | |
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/csky')
| -rw-r--r-- | sysdeps/csky/abiv2/start.S | 17 |
1 files changed, 4 insertions, 13 deletions
diff --git a/sysdeps/csky/abiv2/start.S b/sysdeps/csky/abiv2/start.S index d65e37e..a565cfa 100644 --- a/sysdeps/csky/abiv2/start.S +++ b/sysdeps/csky/abiv2/start.S @@ -66,13 +66,9 @@ _start: .Lgetpc: lrw gb, .Lgetpc@GOTPC addu gb, t0 - lrw a3, __libc_csu_fini@GOT - ldr.w a3, (gb, a3 << 0) - stw a3, (sp, 0) - lrw a3, __libc_csu_init@GOT - addu a3, gb - ldw a3, (a3, 0) + movi a3, 0 /* Used to be init. */ + stw a3, (sp, 0) /* Used to be fini. */ lrw t0, main@GOT addu t0, gb @@ -85,14 +81,9 @@ _start: ldr.w t1, (gb, t1 << 0) jsr t1 #else - /* Fetch address of __libc_csu_fini. */ - lrw a0, __libc_csu_fini - /* Push __libc_csu_fini */ - stw a0, (sp, 0) - - /* Set up the other arguments in registers. */ + movi a3, 0 /* Used to be init. */ + stw a3, (sp, 0) /* Used to be fini. */ lrw a0, main - lrw a3, __libc_csu_init /* Let the libc call main and exit with its return code. */ jsri __libc_start_main |