Since the ORC unwinder from pt_regs requires setting up regs->ip correctly, set the correct return address to the regs->ip before calling user kretprobe handler. This allows the kretrprobe handler to trace stack from the kretprobe's pt_regs by stack_trace_save_regs() (eBPF will do this), instead of stack tracing from the handler context by stack_trace_save() (ftrace will do this). Link: https://lkml.kernel.org/r/163163053237.489837.4272653874525136832.stgit@devnote2
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| @@ -1937,6 +1937,13 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, · 1936 unmodified lines | ||
| 1937 | 1937 | BUG_ON(1); |
| 1938 | 1938 | } |
| 1939 | 1939 | |
| 1940 | + /* | |
| 1941 | + * Set the return address as the instruction pointer, because if the | |
| 1942 | + * user handler calls stack_trace_save_regs() with this 'regs', | |
| 1943 | + * the stack trace will start from the instruction pointer. | |
| 1944 | + */ | |
| 1945 | + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); | |
| 1946 | + | |
| 1940 | 1947 | /* Run the user handler of the nodes. */ |
| 1941 | 1948 | first = current->kretprobe_instances.first; |
| 1942 | 1949 | while (first) { |