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Callers of a stacktrace might pass bad frame pointers. Those are usually checked for safety in stack walking helpers before any dereferencing, but this is not the case when we need to go through one more frame pointer that backlinks the irq stack to the previous one, as we don't have any reliable address boudaries to compare this frame pointer against. This raises crashes when we record callchains for ftrace events with perf because we don't use the right helpers to capture registers there. We get wrong frame pointers as we call task_pt_regs() even on kernel threads, which is a wrong thing as it gives us the initial state of any kernel threads freshly created. This is even not what we want for user tasks. What we want is a hot snapshot of registers when the ftrace event triggers, not the state before a task entered the kernel. This requires more thoughts to do it correctly though. So first put a guardian to ensure the given frame pointer can be dereferenced to avoid crashes. We'll think about how to fix the callers in a subsequent patch. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: 2.6.33.x <stable@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> |
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| boot | ||
| configs | ||
| crypto | ||
| ia32 | ||
| include/asm | ||
| kernel | ||
| kvm | ||
| lguest | ||
| lib | ||
| math-emu | ||
| mm | ||
| oprofile | ||
| pci | ||
| power | ||
| tools | ||
| vdso | ||
| video | ||
| xen | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.cpu | ||
| Kconfig.debug | ||
| Makefile | ||
| Makefile_32.cpu | ||