ARM: oprofile: Fix backtraces in timer mode

Always allow backtraces when using oprofile on ARM, even if a PMU
isn't present. Restores functionality originally introduced in commit
1b7b56982fdcd9d85effd76f3928cf5d6eb26155 ("oprofile: Always allow
backtraces on ARM") by Richard Purdie.

It is not that obvious, but there is now only one oprofile_arch_init()
function. So the .backtrace callback is available also in timer mode.

Implemented by removing code and using stubs for oprofile_perf_{init,
exit} provided by <linux/oprofile.h>. This allows cleaning of other
architecture specific implementations too.

Cc: stable@kernel.org # 37.x
Signed-off-by: Ari Kauppi <kauppi@papupata.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>

1 files changed, 2 insertions, 10 deletions

diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
index 8aa974491dfc..2b663918c464 100644
--- a/arch/arm/oprofile/common.c
+++ b/arch/arm/oprofile/common.c
@@ -10,8 +10,6 @@
  */
 
 #include <linux/cpumask.h>
-#include <linux/err.h>
-#include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/mutex.h>
 #include <linux/oprofile.h>
@@ -46,6 +44,7 @@ char *op_name_from_perf_id(void)
                 return NULL;
         }
 }
+#endif
 
 static int report_trace(struct stackframe *frame, void *d)
 {
@@ -111,6 +110,7 @@ static void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
 
 int __init oprofile_arch_init(struct oprofile_operations *ops)
 {
+        /* provide backtrace support also in timer mode: */
         ops->backtrace          = arm_backtrace;
 
         return oprofile_perf_init(ops);
@@ -120,11 +120,3 @@ void __exit oprofile_arch_exit(void)
 {
         oprofile_perf_exit();
 }
-#else
-int __init oprofile_arch_init(struct oprofile_operations *ops)
-{
-        pr_info("oprofile: hardware counters not available\n");
-        return -ENODEV;
-}
-void __exit oprofile_arch_exit(void) {}
-#endif /* CONFIG_HW_PERF_EVENTS */