Date: Mon, 12 Jan 2004 14:51:23 +0100 From: Marc Olzheim <marcolz@stack.nl> To: Daniel Eischen <eischen@vigrid.com> Cc: hackers@freebsd.org Subject: Re: libc_r/uthread/uthread_join.c and uthread_create.c Message-ID: <20040112135123.GA41657@stack.nl> In-Reply-To: <20031231143015.GA59104@stack.nl> References: <20031231140533.GA56158@stack.nl> <Pine.GSO.4.10.10312310911360.3264-100000@pcnet5.pcnet.com> <20031231143015.GA59104@stack.nl>
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On Wed, Dec 31, 2003 at 03:30:15PM +0100, Marc Olzheim wrote:
> So I noticed. But it seems to me as if the undefers could be removed
> from within the if-else-blocks and collapsed into a single undefer just
> beneath the if-else-blocks, right before the
> _thread_leave_cancellation_point();
Hmm, this is just what OpenBSD did...
Any way: new problem / idea:
uthread_create.c: _pthread_create() doesn't clean ebp, so producing a
backtrace, either with gdb, or with gcc's __builtin_frame_address(),
results in garbage, cq. segmentation faults, when for instance the
spawning thread has already been deleted.
The following patch fixes that for i386. I don't have any other systems
available, so I don't know what to do on other systems, but this works
for us.
Zlo
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--- /usr/src/lib/libc_r/uthread/pthread_private.h Tue Oct 22 16:44:02 2002
+++ /usr/src/lib/libc_r/uthread/pthread_private.h Mon Jan 12 14:34:32 2004
@@ -84,7 +84,8 @@
fdata = (char *) (ucp)->uc_mcontext.mc_fpregs; \
__asm__("frstor %0": :"m"(*fdata)); \
} while (0)
-#define SET_RETURN_ADDR_JB(jb, ra) (jb)[0]._jb[0] = (int)(ra)
+#define SET_RETURN_ADDR_JB(jb, ra) (jb)[0]._jb[0] = (int)(ra)
+#define SET_FRAME_PTR_JB(jb, fp) (jb)[0]._jb[3] = (int)(fp)
#elif defined(__alpha__)
#include <machine/reg.h>
#define GET_STACK_JB(jb) ((unsigned long)((jb)[0]._jb[R_SP + 4]))
--- /usr/src/lib/libc_r/uthread/uthread_create.c Wed Jan 8 06:04:26 2003
+++ /usr/src/lib/libc_r/uthread/uthread_create.c Mon Jan 12 14:23:56 2004
@@ -195,6 +195,7 @@
* _thread_start().
*/
SET_RETURN_ADDR_JB(new_thread->ctx.jb, _thread_start);
+ SET_FRAME_PTR_JB(new_thread->ctx.jb, NULL);
/* The stack starts high and builds down: */
SET_STACK_JB(new_thread->ctx.jb,
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