lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-07-28 00:21:52 +03:00
Code Activity

Reduce the statically linked startup code [BZ #23323]

Browse Source 
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.
This commit is contained in:
Florian Weimer
2021-02-25 12:10:57 +01:00
parent a79328c745
commit 035c012e32
63 changed files with 275 additions and 314 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
sysdeps/sparc/sparc32/start.S
View File

@ -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

12
sysdeps/sparc/sparc64/start.S
View File

@ -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