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ftrace: Fix function_graph tracer interaction with BPF trampoline

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Depending on type of BPF programs served by BPF trampoline it can call original
function. In such case the trampoline will skip one stack frame while
returning. That will confuse function_graph tracer and will cause crashes with
bad RIP. Teach graph tracer to skip functions that have BPF trampoline attached.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Alexei Starovoitov
2019-12-08 16:01:12 -08:00
committed by Steven Rostedt (VMware)
parent a61f810567
commit ff205766db
4 changed files with 21 additions and 26 deletions
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14
arch/x86/kernel/ftrace.c
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@@ -1042,20 +1042,6 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
if (unlikely(atomic_read(&current->tracing_graph_pause)))
return;
/*
* If the return location is actually pointing directly to
* the start of a direct trampoline (if we trace the trampoline
* it will still be offset by MCOUNT_INSN_SIZE), then the
* return address is actually off by one word, and we
* need to adjust for that.
*/
if (ftrace_direct_func_count) {
if (ftrace_find_direct_func(self_addr + MCOUNT_INSN_SIZE)) {
self_addr = *parent;
parent++;
}
}
/*
* Protect against fault, even if it shouldn't
* happen. This tool is too much intrusive to