diff options
Diffstat (limited to 'arch/s390/kernel/ftrace.c')
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 3dabcae40e04..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; @@ -64,9 +71,15 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) return -EFAULT; if (addr == MCOUNT_ADDR) { - /* Initial code replacement; we expect to see stg r14,8(r15) */ + /* 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) { /* |