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fix incorrect __hwcap seen in dynamic-linked __set_thread_area 

the bug fixed in commit b82cd6c78d was
mostly masked on arm because __hwcap was zero at the point of the call
from the dynamic linker to __set_thread_area, causing the access to
libc.auxv to be skipped and kuser_helper versions of TLS access and
atomics to be used instead of the armv6 or v7 versions. however, on
kernels with kuser_helper removed for hardening it would crash.

since __set_thread_area potentially uses __hwcap, it must be
initialized before the function is called. move the AT_HWCAP lookup
from stage 3 to stage 2b.
This commit is contained in:
Rich Felker 2020-01-15 16:15:49 -05:00
parent 2507e7f531
commit 0ff18be208
1 changed files with 1 additions and 1 deletions
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2
ldso/dynlink.c
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@ -1670,6 +1670,7 @@ void __dls2b(size_t *sp, size_t *auxv)
/* Setup early thread pointer in builtin_tls for ldso/libc itself to
* use during dynamic linking. If possible it will also serve as the
* thread pointer at runtime. */
search_vec(auxv, &__hwcap, AT_HWCAP);
libc.auxv = auxv;
libc.tls_size = sizeof builtin_tls;
libc.tls_align = tls_align;
@ -1704,7 +1705,6 @@ void __dls3(size_t *sp, size_t *auxv)
* global data that may be needed before we can make syscalls. */
__environ = envp;
decode_vec(auxv, aux, AUX_CNT);
__hwcap = aux[AT_HWCAP];
search_vec(auxv, &__sysinfo, AT_SYSINFO);
__pthread_self()->sysinfo = __sysinfo;
libc.page_size = aux[AT_PAGESZ];