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ftrace: Fix s390 breakage from sorting mcount tables

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The latest merge of the tracing tree sorts the mcount table at build time.
 But s390 appears to do things differently (like always) and replaces the
 sorted table back to the original unsorted one. As the ftrace algorithm
 depends on it being sorted, bad things happen when it is not, and s390
 experienced those bad things.
 
 Add a new config to tell the boot if the mcount table is sorted or not,
 and allow s390 to opt out of it.
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Merge tag 'trace-v5.17-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull ftrace fix from Steven Rostedt:
 "Fix s390 breakage from sorting mcount tables.

  The latest merge of the tracing tree sorts the mcount table at build
  time. But s390 appears to do things differently (like always) and
  replaces the sorted table back to the original unsorted one. As the
  ftrace algorithm depends on it being sorted, bad things happen when it
  is not, and s390 experienced those bad things.

  Add a new config to tell the boot if the mcount table is sorted or
  not, and allow s390 to opt out of it"

* tag 'trace-v5.17-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  ftrace: Fix assuming build time sort works for s390
This commit is contained in:
Linus Torvalds 2022-01-23 08:07:02 +02:00
commit 67bfce0e01
2 changed files with 10 additions and 3 deletions
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9
kernel/trace/Kconfig
View File

@ -70,6 +70,13 @@ config HAVE_C_RECORDMCOUNT
help
C version of recordmcount available?
config BUILDTIME_MCOUNT_SORT
bool
default y
depends on BUILDTIME_TABLE_SORT && !S390
help
Sort the mcount_loc section at build time.
config TRACER_MAX_TRACE
bool
@ -918,7 +925,7 @@ config EVENT_TRACE_TEST_SYSCALLS
config FTRACE_SORT_STARTUP_TEST
bool "Verify compile time sorting of ftrace functions"
depends on DYNAMIC_FTRACE
depends on BUILDTIME_TABLE_SORT
depends on BUILDTIME_MCOUNT_SORT
help
Sorting of the mcount_loc sections that is used to find the
where the ftrace knows where to patch functions for tracing

4
kernel/trace/ftrace.c
View File

@ -6435,10 +6435,10 @@ static int ftrace_process_locs(struct module *mod,
/*
* Sorting mcount in vmlinux at build time depend on
* CONFIG_BUILDTIME_TABLE_SORT, while mcount loc in
* CONFIG_BUILDTIME_MCOUNT_SORT, while mcount loc in
* modules can not be sorted at build time.
*/
if (!IS_ENABLED(CONFIG_BUILDTIME_TABLE_SORT) || mod) {
if (!IS_ENABLED(CONFIG_BUILDTIME_MCOUNT_SORT) || mod) {
sort(start, count, sizeof(*start),
ftrace_cmp_ips, NULL);
} else {