MIPS: Extract schedule_mfi info from __schedule (5000653e) · Commits · 戴 / test

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>

arch/mips/kernel/process.c

+32 −2

Original line number	Diff line number	Diff line
		@@ -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);

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