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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/s390/s390-32/start.S | |
| 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/s390/s390-32/start.S')
| -rw-r--r-- | sysdeps/s390/s390-32/start.S | 10 |
1 files changed, 2 insertions, 8 deletions
diff --git a/sysdeps/s390/s390-32/start.S b/sysdeps/s390/s390-32/start.S index aba90739c1..b6cfa4caf3 100644 --- a/sysdeps/s390/s390-32/start.S +++ b/sysdeps/s390/s390-32/start.S @@ -175,18 +175,16 @@ _start: */ stm %r14,%r15,96(%r15) # store rtld_fini/stack_end to parameter area la %r7,96(%r15) - l %r6,.L2-.Llit(%r13) # load pointer to __libc_csu_fini - l %r5,.L1-.Llit(%r13) # load pointer to __libc_csu_init l %r2,.L3-.Llit(%r13) # load pointer to main l %r1,.L4-.Llit(%r13) # load pointer to __libc_start_main #ifdef PIC l %r12,.L5-.Llit(%r13) # load .got pointer - la %r6,0(%r13,%r6) - la %r5,0(%r13,%r5) la %r12,0(%r13,%r12) l %r2,0(%r12,%r2) la %r1,0(%r13,%r1) #endif + lhi %r6, 0 # Used to fini. + lhi %r5, 0 # Used to init. /* ok, now branch to the libc main routine */ basr %r14,%r1 @@ -197,13 +195,9 @@ _start: cfi_endproc .Llit: #ifndef PIC -.L1: .long __libc_csu_init -.L2: .long __libc_csu_fini .L3: .long main .L4: .long __libc_start_main #else -.L1: .long __libc_csu_init-.Llit -.L2: .long __libc_csu_fini-.Llit .L3: .long main@GOT .L4: .long __libc_start_main@plt-.Llit .L5: .long _GLOBAL_OFFSET_TABLE_-.Llit |