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Diffstat (limited to 'arch/s390/kernel/ftrace.c')
-rw-r--r--arch/s390/kernel/ftrace.c108
1 files changed, 62 insertions, 46 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index b86bb8823f15..82c19899574f 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -46,6 +46,13 @@
* lg %r14,8(%r15) # offset 18
* The jg instruction branches to offset 24 to skip as many instructions
* as possible.
+ * In case we use gcc's hotpatch feature the original and also the disabled
+ * function prologue contains only a single six byte instruction and looks
+ * like this:
+ * > brcl 0,0 # offset 0
+ * To enable ftrace the code gets patched like above and afterwards looks
+ * like this:
+ * > brasl %r0,ftrace_caller # offset 0
*/
unsigned long ftrace_plt;
@@ -59,62 +66,71 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
- struct ftrace_insn insn;
- unsigned short op;
- void *from, *to;
- size_t size;
-
- ftrace_generate_nop_insn(&insn);
- size = sizeof(insn);
- from = &insn;
- to = (void *) rec->ip;
- if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op)))
+ struct ftrace_insn orig, new, old;
+
+ if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
return -EFAULT;
- /*
- * If we find a breakpoint instruction, a kprobe has been placed
- * at the beginning of the function. We write the constant
- * KPROBE_ON_FTRACE_NOP into the remaining four bytes of the original
- * instruction so that the kprobes handler can execute a nop, if it
- * reaches this breakpoint.
- */
- if (op == BREAKPOINT_INSTRUCTION) {
- size -= 2;
- from += 2;
- to += 2;
- insn.disp = KPROBE_ON_FTRACE_NOP;
+ if (addr == MCOUNT_ADDR) {
+ /* Initial code replacement */
+#ifdef CC_USING_HOTPATCH
+ /* We expect to see brcl 0,0 */
+ ftrace_generate_nop_insn(&orig);
+#else
+ /* We expect to see stg r14,8(r15) */
+ orig.opc = 0xe3e0;
+ orig.disp = 0xf0080024;
+#endif
+ ftrace_generate_nop_insn(&new);
+ } else if (old.opc == BREAKPOINT_INSTRUCTION) {
+ /*
+ * If we find a breakpoint instruction, a kprobe has been
+ * placed at the beginning of the function. We write the
+ * constant KPROBE_ON_FTRACE_NOP into the remaining four
+ * bytes of the original instruction so that the kprobes
+ * handler can execute a nop, if it reaches this breakpoint.
+ */
+ new.opc = orig.opc = BREAKPOINT_INSTRUCTION;
+ orig.disp = KPROBE_ON_FTRACE_CALL;
+ new.disp = KPROBE_ON_FTRACE_NOP;
+ } else {
+ /* Replace ftrace call with a nop. */
+ ftrace_generate_call_insn(&orig, rec->ip);
+ ftrace_generate_nop_insn(&new);
}
- if (probe_kernel_write(to, from, size))
+ /* Verify that the to be replaced code matches what we expect. */
+ if (memcmp(&orig, &old, sizeof(old)))
+ return -EINVAL;
+ if (probe_kernel_write((void *) rec->ip, &new, sizeof(new)))
return -EPERM;
return 0;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
- struct ftrace_insn insn;
- unsigned short op;
- void *from, *to;
- size_t size;
-
- ftrace_generate_call_insn(&insn, rec->ip);
- size = sizeof(insn);
- from = &insn;
- to = (void *) rec->ip;
- if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op)))
+ struct ftrace_insn orig, new, old;
+
+ if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
return -EFAULT;
- /*
- * If we find a breakpoint instruction, a kprobe has been placed
- * at the beginning of the function. We write the constant
- * KPROBE_ON_FTRACE_CALL into the remaining four bytes of the original
- * instruction so that the kprobes handler can execute a brasl if it
- * reaches this breakpoint.
- */
- if (op == BREAKPOINT_INSTRUCTION) {
- size -= 2;
- from += 2;
- to += 2;
- insn.disp = KPROBE_ON_FTRACE_CALL;
+ if (old.opc == BREAKPOINT_INSTRUCTION) {
+ /*
+ * If we find a breakpoint instruction, a kprobe has been
+ * placed at the beginning of the function. We write the
+ * constant KPROBE_ON_FTRACE_CALL into the remaining four
+ * bytes of the original instruction so that the kprobes
+ * handler can execute a brasl if it reaches this breakpoint.
+ */
+ new.opc = orig.opc = BREAKPOINT_INSTRUCTION;
+ orig.disp = KPROBE_ON_FTRACE_NOP;
+ new.disp = KPROBE_ON_FTRACE_CALL;
+ } else {
+ /* Replace nop with an ftrace call. */
+ ftrace_generate_nop_insn(&orig);
+ ftrace_generate_call_insn(&new, rec->ip);
}
- if (probe_kernel_write(to, from, size))
+ /* Verify that the to be replaced code matches what we expect. */
+ if (memcmp(&orig, &old, sizeof(old)))
+ return -EINVAL;
+ if (probe_kernel_write((void *) rec->ip, &new, sizeof(new)))
return -EPERM;
return 0;
}