From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.0) Gecko/20020529 Description of problem: setcontext() temporarily stores the new register values on the stack at addresses less than the stack pointer (before 'popa' to set the new values). If a signal is delivered between the store and the popa, then the locations that are read by popa get overwritten, so eventually the wrong values will be set into the registers. Version-Release number of selected component (if applicable): glibc-2.3.2-11.9 How reproducible: Always Steps to Reproduce: 1.Run testcase stdlib/tst-setcontext under gdb. 2.Set a breakpoint at setcontext+67: mov %ebx,(%ecx) 3.Print $ecx and $esp at the breakpoint. Actual Results: $esp = 0xffffcb1c $ecx = 0xffffcafc # 0x20 less than $esp Expected Results: $esp = 0xffffcafc $ecx = 0xffffcafc # == $esp Additional info: Fix: move the "movl %ecx, %esp" at line 85 of sysdeps/unix/sysv/linux/i386/setcontext.S to just after the "subl $36, %ecx" at line 60.
A similar problem exists in sysdeps/unix/sysv/linux/i386/swapcontext.S at lines 89 and 114.
An errata has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2003-136.html