[pushed] Block signals during the initial part of dlopen
Commit Message
* Florian Weimer:
> * Joseph Myers:
>
>> On Wed, 27 Nov 2019, Sourceware to Gerrit sync (Code Review) wrote:
>>
>>> Block signals during the initial part of dlopen
>>>
>>> Lazy binding in a signal handler that interrupts a dlopen sees
>>> intermediate dynamic linker state. This has likely been always
>>> unsafe, but with the new pending NODELETE state, this is clearly
>>> incorrect. Other threads are excluded via the loader lock, but the
>>> current thread is not. Blocking signals until right before ELF
>>> constructors run is the safe thing to do.
>>
>> This change (commit a2e8aa0d9ea648068d8be52dd7b15f1b6a008e23) breaks the
>> build for i686-gnu (unfortunately this was after a syntax error was
>> introduced in build-many-glibcs.py so my bots quietly died on re-execing
>> with the syntax error, and so didn't get to find this build failure).
>>
>> There are a series of errors linking ld.so starting with:
>>
>> /scratch/jmyers/glibc/many9/install/compilers/i686-gnu/lib/gcc/i686-glibc-gnu/9.2.1/../../../../i686-glibc-gnu/bin/ld:
>> /scratch/jmyers/glibc/many9/build/glibcs/i686-gnu/glibc/libc_pic.a(libc_fatal.os):
>> in function `__GI___libc_fatal':
>> /scratch/jmyers/glibc/many9/src/glibc/libio/../sysdeps/posix/libc_fatal.c:161:
>> multiple definition of `__libc_fatal';
>> /scratch/jmyers/glibc/many9/build/glibcs/i686-gnu/glibc/elf/dl-allobjs.os:/scratch/jmyers/glibc/many9/src/glibc/elf/dl-minimal.c:188:
>> first defined here
>>
>> and leading up to:
>>
>> make[3]: ***
>> [/scratch/jmyers/glibc/many9/build/glibcs/i686-gnu/glibc/elf/librtld.map]
>> Error 1
>
> I failed to test the later commits using build-many-glibcs.py because
> I deemed them more straightforward.
>
> The patch below should fix it.
Posted too soon. The localplt update was missing.
8<------------------------------------------------------------------8<
hurd: Add stub implementation of __sigprocmask to the dynamic loader
The actual __sigprocmask cannot be built for the loader since it
depends on per-thread state.
Fixes commit a2e8aa0d9ea648068d8be52dd7b15f1b6a008e23 ("Block signals
during the initial part of dlopen").
@@ -41,6 +41,6 @@ ld {
# functions that must be shared with libc
__access_noerrno; __libc_read; __libc_write; __libc_lseek64;
- __libc_lock_self0;
+ __libc_lock_self0; __sigprocmask;
}
}
@@ -693,6 +693,15 @@ _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
timeout, notify);
}
+/* This function does nothing and will be interposed with the actual
+ implementation once is libc is loaded. Before that, manipulating
+ the signal mask does not make sense because no signal handlers have
+ been installed. */
+int weak_function
+__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
+{
+ return 0;
+}
void
_dl_show_auxv (void)
@@ -41,6 +41,7 @@ ld.so: __strtoul_internal
#ld.so: _exit
ld.so: abort
ld.so: _hurd_intr_rpc_mach_msg
+ld.so: __sigprocmask
ld.so: __errno_location
# rtld_hidden is currently disabled to avoid having to special-case the
# functions above which do need a PLT. These are thus currently expected.