Date: Thu, 20 Dec 2018 12:59:06 +0400 From: Gleb Popov <arrowd@freebsd.org> To: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Calling a function from a SO breaks in libc Message-ID: <CALH631m4D-wNNYY-YwZ%2BvyNohiZ3sD3VpOQYDKihPnmEuBmCrw@mail.gmail.com>
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When debugging software with GDB on FreeBSD 12+ I often get into following
situation:
(gdb) next
(anonymous namespace)::D13AsmPrinter::EmitInstruction (this=0x8056b4b80,
MI=0x805765690) at
/home/arr/projects/d13/lib/Target/D13/D13AsmPrinter.cpp:152
152 EmitToStreamer(*OutStreamer, TmpInst);
(gdb) step
Now instead of entering into EmitStreamer(), I see:
_thr_rtld_set_flag (mask=1) at /usr/src/lib/libthr/thread/thr_rtld.c:171
171 {
Trying to get out of there:
(gdb) finish
Run till exit from #0 _thr_rtld_set_flag (mask=1) at
/usr/src/lib/libthr/thread/thr_rtld.c:171
0x000000080027669b in thread_mask_set (mask=<optimized out>) at
/usr/src/libexec/rtld-elf/rtld_lock.c:177
177 return lockinfo.thread_set_flag(mask);
Value returned is $3 = 0
(gdb) finish
Run till exit from #0 0x000000080027669b in thread_mask_set
(mask=<optimized out>) at /usr/src/libexec/rtld-elf/rtld_lock.c:177
rlock_acquire (lock=0x800287ba0 <rtld_locks>, lockstate=0x7fffffff9608) at
/usr/src/libexec/rtld-elf/rtld_lock.c:203
203 if (thread_mask_set(lock->mask) & lock->mask) {
(gdb) finish
Run till exit from #0 rlock_acquire (lock=0x800287ba0 <rtld_locks>,
lockstate=0x7fffffff9608) at /usr/src/libexec/rtld-elf/rtld_lock.c:203
_rtld_bind (obj=0x80028b400, reloff=625152) at
/usr/src/libexec/rtld-elf/rtld.c:808
808 if (sigsetjmp(lockstate.env, 0) != 0)
(gdb) finish
Run till exit from #0 _rtld_bind (obj=0x80028b400, reloff=625152) at
/usr/src/libexec/rtld-elf/rtld.c:808
_rtld_bind_start () at /usr/src/libexec/rtld-elf/amd64/rtld_start.S:124
124 movq %rax,0x60(%rsp) # Store target over reloff
argument
Value returned is $4 = 34402603952
(gdb) finish
Run till exit from #0 _rtld_bind_start () at
/usr/src/libexec/rtld-elf/amd64/rtld_start.S:124
Program received signal SIGTRAP, Trace/breakpoint trap.
_rtld_bind_start () at /usr/src/libexec/rtld-elf/amd64/rtld_start.S:155
155 ret # "Return" to target address
(gdb) finish
Run till exit from #0 _rtld_bind_start () at
/usr/src/libexec/rtld-elf/amd64/rtld_start.S:155
Program received signal SIGTRAP, Trace/breakpoint trap.
0x00000008028e13b4 in llvm::AsmPrinter::EmitToStreamer (this=0x80028b400,
S=..., Inst=...) at
/home/arr/projects/d13/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:228
After this. the debugging is impossible, because every "cont/step/next"
command yields "Program received signal SIGTRAP, Trace/breakpoint trap".
Trying to "print" anything causes GDB to crash.
It should be noted, that I'm linking to LLVM-7.so library. Using static
linkage for the executable I'm debugging makes this bug go away.
Anyone have an idea what's going on and how to fix that?
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