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Replace __libc_multiple_libcs with __libc_initial flag

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Change sbrk to fail for !__libc_initial (in the generic
implementation).  As a result, sbrk is (relatively) safe to use
for the __libc_initial case (from the main libc).  It is therefore
no longer necessary to avoid using it in that case (or updating the
brk cache), and the __libc_initial flag does not need to be updated
as part of dlmopen or static dlopen.

As before, direct brk system calls on Linux may lead to memory
corruption.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer
2020-12-16 15:09:52 +01:00
parent 9459fe9da0
commit e7570f4131
9 changed files with 52 additions and 39 deletions
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13
csu/libc-start.c
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@ -141,8 +141,6 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
/* Result of the 'main' function. */
int result;
__libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
#ifndef SHARED
_dl_relocate_static_pie ();
@ -213,12 +211,11 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
# endif
# ifdef DL_SYSDEP_OSCHECK
if (!__libc_multiple_libcs)
{
/* This needs to run to initiliaze _dl_osversion before TLS
setup might check it. */
DL_SYSDEP_OSCHECK (__libc_fatal);
}
{
/* This needs to run to initiliaze _dl_osversion before TLS
setup might check it. */
DL_SYSDEP_OSCHECK (__libc_fatal);
}
# endif
/* Initialize libpthread if linked in. */