Commit 474f8196 authored by Roland McGrath's avatar Roland McGrath Committed by Paul Mackerras

[POWERPC] Ensure FULL_REGS on exec

When PTRACE_O_TRACEEXEC is used, a ptrace call to fetch the registers at
the PTRACE_EVENT_EXEC stop (PTRACE_PEEKUSR) will oops in CHECK_FULL_REGS.
With recent versions, "gdb --args /bin/sh -c 'exec /bin/true'" and "run" at
the (gdb) prompt is sufficient to produce this.  I also have written an
isolated test case, see https://bugzilla.redhat.com/show_bug.cgi?id=301791#c15.

This change fixes the problem by clearing the low bit of pt_regs.trap in
start_thread so that FULL_REGS is true again.  This is correct since all of
the GPRs that "full" refers to are cleared in start_thread.
Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 4942de4a
......@@ -605,6 +605,13 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
regs->ccr = 0;
regs->gpr[1] = sp;
/*
* We have just cleared all the nonvolatile GPRs, so make
* FULL_REGS(regs) return true. This is necessary to allow
* ptrace to examine the thread immediately after exec.
*/
regs->trap &= ~1UL;
#ifdef CONFIG_PPC32
regs->mq = 0;
regs->nip = start;
......
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