From 5000653e923de49aa282fd7d172eb6528c3ec5c7 Mon Sep 17 00:00:00 2001 From: Tony Wu Date: Sun, 12 May 2013 15:05:34 +0000 Subject: [PATCH] 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 Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/5237/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/process.c | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index 785bf2a4129a..a682a87bcc04 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -224,6 +224,9 @@ struct mips_frame_info { 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 @@ err: 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; +#endif + unsigned long addr; - kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs); + addr = get___schedule_addr(); + if (!addr) + addr = (unsigned long)schedule; + +#ifdef CONFIG_KALLSYMS + kallsyms_lookup_size_offset(addr, &size, &ofs); #endif - schedule_mfi.func = schedule; + schedule_mfi.func = (void *)addr; schedule_mfi.func_size = size; get_frame_info(&schedule_mfi); -- 2.20.1