diff options
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 41 | ||||
| -rw-r--r-- | arch/x86/kernel/ftrace_64.S | 8 |
2 files changed, 26 insertions, 23 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 7ee8067cbf45..8257a59704ae 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -733,18 +733,20 @@ union ftrace_op_code_union { } __attribute__((packed)); }; +#define RET_SIZE 1 + static unsigned long create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) { - unsigned const char *jmp; unsigned long start_offset; unsigned long end_offset; unsigned long op_offset; unsigned long offset; unsigned long size; - unsigned long ip; + unsigned long retq; unsigned long *ptr; void *trampoline; + void *ip; /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */ unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; union ftrace_op_code_union op_ptr; @@ -764,27 +766,27 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) /* * Allocate enough size to store the ftrace_caller code, - * the jmp to ftrace_epilogue, as well as the address of - * the ftrace_ops this trampoline is used for. + * the iret , as well as the address of the ftrace_ops this + * trampoline is used for. */ - trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *)); + trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *)); if (!trampoline) return 0; - *tramp_size = size + MCOUNT_INSN_SIZE + sizeof(void *); + *tramp_size = size + RET_SIZE + sizeof(void *); /* Copy ftrace_caller onto the trampoline memory */ ret = probe_kernel_read(trampoline, (void *)start_offset, size); - if (WARN_ON(ret < 0)) { - tramp_free(trampoline, *tramp_size); - return 0; - } + if (WARN_ON(ret < 0)) + goto fail; - ip = (unsigned long)trampoline + size; + ip = trampoline + size; - /* The trampoline ends with a jmp to ftrace_epilogue */ - jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_epilogue); - memcpy(trampoline + size, jmp, MCOUNT_INSN_SIZE); + /* The trampoline ends with ret(q) */ + retq = (unsigned long)ftrace_stub; + ret = probe_kernel_read(ip, (void *)retq, RET_SIZE); + if (WARN_ON(ret < 0)) + goto fail; /* * The address of the ftrace_ops that is used for this trampoline @@ -794,17 +796,15 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) * the global function_trace_op variable. */ - ptr = (unsigned long *)(trampoline + size + MCOUNT_INSN_SIZE); + ptr = (unsigned long *)(trampoline + size + RET_SIZE); *ptr = (unsigned long)ops; op_offset -= start_offset; memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE); /* Are we pointing to the reference? */ - if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) { - tramp_free(trampoline, *tramp_size); - return 0; - } + if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) + goto fail; /* Load the contents of ptr into the callback parameter */ offset = (unsigned long)ptr; @@ -819,6 +819,9 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; return (unsigned long)trampoline; +fail: + tramp_free(trampoline, *tramp_size); + return 0; } static unsigned long calc_trampoline_call_offset(bool save_regs) diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index 91b2cff4b79a..75f2b36b41a6 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -171,9 +171,6 @@ GLOBAL(ftrace_call) restore_mcount_regs /* - * The copied trampoline must call ftrace_epilogue as it - * still may need to call the function graph tracer. - * * The code up to this label is copied into trampolines so * think twice before adding any new code or changing the * layout here. @@ -185,7 +182,10 @@ GLOBAL(ftrace_graph_call) jmp ftrace_stub #endif -/* This is weak to keep gas from relaxing the jumps */ +/* + * This is weak to keep gas from relaxing the jumps. + * It is also used to copy the retq for trampolines. + */ WEAK(ftrace_stub) retq ENDPROC(ftrace_caller) |