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authorIlya Leoshkevich <iii@linux.ibm.com>2021-07-29 00:25:45 +0300
committerHeiko Carstens <hca@linux.ibm.com>2021-08-03 15:31:40 +0300
commit67ccddf86621b18dbffe56f11a106774ee8f44bd (patch)
treecbc130b1c3c4da92e7c87b8cd5c70942e697ab60 /kernel/trace/ftrace.c
parentd80d3ea64e5fa2ab20b3774ea0d871484877422b (diff)
downloadlinux-67ccddf86621b18dbffe56f11a106774ee8f44bd.tar.xz
ftrace: Introduce ftrace_need_init_nop()
Implementing live patching on s390 requires each function's prologue to contain a very special kind of nop, which gcc and clang don't generate. However, the current code assumes that if CC_USING_NOP_MCOUNT is defined, then whatever the compiler generates is good enough. Move the CC_USING_NOP_MCOUNT check into the new ftrace_need_init_nop() macro, that the architectures can override. An alternative solution is to disable using -mnop-mcount in the Makefile, however, this makes the build logic (even) more complicated and forces the arch-specific code to deal with the useless __fentry__ symbol. Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20210728212546.128248-2-iii@linux.ibm.com Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'kernel/trace/ftrace.c')
-rw-r--r--kernel/trace/ftrace.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7b180f61e6d3..7efbc8aaf7f6 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3100,6 +3100,7 @@ ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
{
+ bool init_nop = ftrace_need_init_nop();
struct ftrace_page *pg;
struct dyn_ftrace *p;
u64 start, stop;
@@ -3138,8 +3139,7 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
* Do the initial record conversion from mcount jump
* to the NOP instructions.
*/
- if (!__is_defined(CC_USING_NOP_MCOUNT) &&
- !ftrace_nop_initialize(mod, p))
+ if (init_nop && !ftrace_nop_initialize(mod, p))
break;
update_cnt++;