MIPS: Extract schedule_mfi info from __schedule
schedule_mfi is supposed to be extracted from schedule(), and
is used in thread_saved_pc and get_wchan.
But, after optimization, schedule() is reduced to a sibling
call to __schedule(), and no real frame info can be extracted.
One solution is to compile schedule() with -fno-omit-frame-pointer
and -fno-optimize-sibling-calls, but that will incur performance
degradation.
Another solution is to extract info from the real scheduler,
__schedule, and this is the approache adopted here.
This patch reads the __schedule address by either following
the 'j' call in schedule if KALLSYMS is disabled or by using
kallsyms_lookup_name to lookup __schedule if KALLSYMS is
available, then, extracts schedule_mfi from __schedule frame info.
This patch also fixes the "Can't analyze schedule() prologue"
warning at boot time.
Signed-off-by: Tony Wu <tung7970@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5237/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 785bf2a..a682a87 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -224,6 +224,9 @@
int pc_offset;
};
+#define J_TARGET(pc,target) \
+ (((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
+
static inline int is_ra_save_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
@@ -395,15 +398,42 @@
static struct mips_frame_info schedule_mfi __read_mostly;
+#ifdef CONFIG_KALLSYMS
+static unsigned long get___schedule_addr(void)
+{
+ return kallsyms_lookup_name("__schedule");
+}
+#else
+static unsigned long get___schedule_addr(void)
+{
+ union mips_instruction *ip = (void *)schedule;
+ int max_insns = 8;
+ int i;
+
+ for (i = 0; i < max_insns; i++, ip++) {
+ if (ip->j_format.opcode == j_op)
+ return J_TARGET(ip, ip->j_format.target);
+ }
+ return 0;
+}
+#endif
+
static int __init frame_info_init(void)
{
unsigned long size = 0;
#ifdef CONFIG_KALLSYMS
unsigned long ofs;
-
- kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
#endif
- schedule_mfi.func = schedule;
+ unsigned long addr;
+
+ addr = get___schedule_addr();
+ if (!addr)
+ addr = (unsigned long)schedule;
+
+#ifdef CONFIG_KALLSYMS
+ kallsyms_lookup_size_offset(addr, &size, &ofs);
+#endif
+ schedule_mfi.func = (void *)addr;
schedule_mfi.func_size = size;
get_frame_info(&schedule_mfi);
