On x86-64, when glibc is configured with --enable-stack-protector=all
and compiled with -Os, ld.so crashes very early:
(gdb) r --direct
Starting program: /export/build/gnu/tools-build/glibc-gitlab/build-x86_64-linux/string/test-memswap --direct
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7f41b0a in bsearch (__key=__key@entry=0x7fffffffda28,
__base=__base@entry=0x7ffff7fca140 <intel_02_known>,
__nmemb=__nmemb@entry=68, __size=__size@entry=8,
__compar=__compar@entry=0x7ffff7f3b691 <intel_02_known_compare>)
at ../bits/stdlib-bsearch.h:22
22 {
(gdb) disass
Dump of assembler code for function bsearch:
0x00007ffff7f41af0 <+0>: push %r15
0x00007ffff7f41af2 <+2>: mov %rcx,%r15
0x00007ffff7f41af5 <+5>: push %r14
0x00007ffff7f41af7 <+7>: push %r13
0x00007ffff7f41af9 <+9>: mov %rsi,%r13
0x00007ffff7f41afc <+12>: push %r12
0x00007ffff7f41afe <+14>: mov %rdi,%r12
0x00007ffff7f41b01 <+17>: push %rbp
0x00007ffff7f41b02 <+18>: mov %rdx,%rbp
0x00007ffff7f41b05 <+21>: push %rbx
0x00007ffff7f41b06 <+22>: sub $0x18,%rsp
=> 0x00007ffff7f41b0a <+26>: mov %fs:0x28,%r14
^^^^^^^^^^^^^^^^^^^^^^^^^^^^ We can't use stack protector at this point.
0x00007ffff7f41b13 <+35>: mov %r14,0x8(%rsp)
0x00007ffff7f41b18 <+40>: mov %r8,%r14
0x00007ffff7f41b1b <+43>: test %rbp,%rbp
0x00007ffff7f41b1e <+46>: je 0x7ffff7f41b48 <bsearch+88>
0x00007ffff7f41b20 <+48>: mov %rbp,%rbx
0x00007ffff7f41b23 <+51>: mov %r12,%rdi
0x00007ffff7f41b26 <+54>: shr $1,%rbx
0x00007ffff7f41b29 <+57>: imul %r15,%rbx
0x00007ffff7f41b2d <+61>: add %r13,%rbx
0x00007ffff7f41b30 <+64>: mov %rbx,%rsi
(gdb) bt
#0 0x00007ffff7f41b0a in bsearch (__key=__key@entry=0x7fffffffda28,
__base=__base@entry=0x7ffff7fca140 <intel_02_known>,
__nmemb=__nmemb@entry=68, __size=__size@entry=8,
__compar=__compar@entry=0x7ffff7f3b691 <intel_02_known_compare>)
at ../bits/stdlib-bsearch.h:22
#1 0x00007ffff7f3c1be in intel_check_word (name=188, value=
1979933440,
has_level_2=has_level_2@entry=0x7fffffffda7f,
no_level_2_or_3=no_level_2_or_3@entry=0x7fffffffda7e,
cpu_features=<optimized out>) at ../sysdeps/x86/dl-cacheinfo.h:217
#2 0x00007ffff7f3c29f in handle_intel (name=name@entry=188,
cpu_features=<optimized out>) at ../sysdeps/x86/dl-cacheinfo.h:279
#3 0x00007ffff7f3ccf9 in dl_init_cacheinfo (cpu_features=<optimized out>)
at ../sysdeps/x86/dl-cacheinfo.h:852
#4 init_cpu_features (cpu_features=<optimized out>)
at ../sysdeps/x86/cpu-features.c:1153
#5 0x00007ffff7f3d6f9 in __libc_start_main_impl (main=0x7ffff7f396dc <main>,
argc=2, argv=0x7fffffffdbe8, init=<optimized out>, fini=<optimized out>,
rtld_fini=0x0, stack_end=0x7fffffffdbd8) at ../csu/libc-start.c:269
#6 0x00007ffff7f39901 in _start () at ../sysdeps/x86_64/start.S:115
(gdb)
The problem is that since __USE_EXTERN_INLINES isn't defined with -Os,
the inline bsearch in <bits/stdlib-bsearch.h> isn't available and the
external bsearch is compiled with stack protector. Include
<bits/stdlib-bsearch.h> in dl-cacheinfo.h fixed BZ #33374.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>