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authorJosh Poimboeuf <jpoimboe@redhat.com>2020-07-17 09:04:25 -0500
committerThomas Gleixner <tglx@linutronix.de>2020-07-22 23:47:47 +0200
commit372a8eaa05998cd45b3417d0e0ffd3a70978211a (patch)
tree09a908e123a2665e0804122640bb6c9741309da5 /arch
parentde2b41be8fcccb2f5b6c480d35df590476344201 (diff)
x86/unwind/orc: Fix ORC for newly forked tasks
The ORC unwinder fails to unwind newly forked tasks which haven't yet run on the CPU. It correctly reads the 'ret_from_fork' instruction pointer from the stack, but it incorrectly interprets that value as a call stack address rather than a "signal" one, so the address gets incorrectly decremented in the call to orc_find(), resulting in bad ORC data. Fix it by forcing 'ret_from_fork' frames to be signal frames. Reported-by: Wang ShaoBo <bobo.shaobowang@huawei.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Wang ShaoBo <bobo.shaobowang@huawei.com> Link: https://lkml.kernel.org/r/f91a8778dde8aae7f71884b5df2b16d552040441.1594994374.git.jpoimboe@redhat.com
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/unwind_orc.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 7f969b2d240f..ec88bbe08a32 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -440,8 +440,11 @@ bool unwind_next_frame(struct unwind_state *state)
/*
* Find the orc_entry associated with the text address.
*
- * Decrement call return addresses by one so they work for sibling
- * calls and calls to noreturn functions.
+ * For a call frame (as opposed to a signal frame), state->ip points to
+ * the instruction after the call. That instruction's stack layout
+ * could be different from the call instruction's layout, for example
+ * if the call was to a noreturn function. So get the ORC data for the
+ * call instruction itself.
*/
orc = orc_find(state->signal ? state->ip : state->ip - 1);
if (!orc) {
@@ -662,6 +665,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
state->sp = task->thread.sp;
state->bp = READ_ONCE_NOCHECK(frame->bp);
state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
+ state->signal = (void *)state->ip == ret_from_fork;
}
if (get_stack_info((unsigned long *)state->sp, state->task,