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, 9 insertions, 0 deletions

diff --git a/include/linux/oprofile.h b/include/linux/oprofile.h
index 54c83827f913..1ca64113efe8 100644
--- a/include/linux/oprofile.h
+++ b/include/linux/oprofile.h
@@ -16,6 +16,8 @@
 #include <linux/types.h>
 #include <linux/spinlock.h>
 #include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/printk.h>
 #include <asm/atomic.h>
  
 /* Each escaped entry is prefixed by ESCAPE_CODE
@@ -190,6 +192,13 @@ int oprofile_write_commit(struct op_entry *entry);
 int __init oprofile_perf_init(struct oprofile_operations *ops);
 void oprofile_perf_exit(void);
 char *op_name_from_perf_id(void);
+#else
+static inline int __init oprofile_perf_init(struct oprofile_operations *ops)
+{
+        pr_info("oprofile: hardware counters not available\n");
+        return -ENODEV;
+}
+static inline void oprofile_perf_exit(void) { }
 #endif /* CONFIG_HW_PERF_EVENTS */
 
 #endif /* OPROFILE_H */