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Diffstat (limited to 'arch/x86/kernel/ftrace.c')
-rw-r--r--arch/x86/kernel/ftrace.c41
1 files changed, 22 insertions, 19 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)