Commit dc74a9e8 authored by Jinyang He's avatar Jinyang He Committed by Huacai Chen
Browse files

LoongArch: Add generic ex-handler unwind in prologue unwinder 



When exception is triggered, code flow go handle_\exception in some
cases. One of stackframe in this case as follows,

high -> +-------+
        | REGS  |  <- a pt_regs
        |       |
        |       |  <- ex trigger
        | REGS  |  <- ex pt_regs   <-+
        |       |                    |
        |       |                    |
low  -> +-------+           ->unwind-+

When unwinder unwinds to handler_\exception it cannot go on prologue
analysis. Because it is an asynchronous code flow, we should get the
next frame PC from regs->csr_era rather than regs->regs[1]. At init time
we copy the handlers to eentry and also copy them to NUMA-affine memory
named pcpu_handlers if NUMA is enabled. Thus, unwinder cannot unwind
normally. To solve this, we try to give some hints in handler_\exception
and fixup unwinders in unwind_next_frame().

Reported-by: default avatarQing Zhang <zhangqing@loongson.cn>
Signed-off-by: default avatarJinyang He <hejinyang@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent c5ac25e0

arch/loongarch/include/asm/unwind.h

+1 −1
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ struct unwind_state { 
	char type; /* UNWINDER_XXX */

	struct stack_info stack_info;

	struct task_struct *task;

	bool first, error, is_ftrace;

	bool first, error, reset;

	int graph_idx;

	unsigned long sp, pc, ra;

};

arch/loongarch/kernel/genex.S

+3 −0
Original line number Diff line number Diff line
@@ -67,14 +67,17 @@ SYM_FUNC_END(except_vec_cex) 
	.macro	BUILD_HANDLER exception handler prep

	.align	5

	SYM_FUNC_START(handle_\exception)

	666:

	BACKUP_T0T1

	SAVE_ALL

	build_prep_\prep

	move	a0, sp

	la.abs	t0, do_\handler

	jirl	ra, t0, 0

	668:

	RESTORE_ALL_AND_RET

	SYM_FUNC_END(handle_\exception)

	SYM_DATA(unwind_hint_\exception, .word 668b - 666b)

	.endm



	BUILD_HANDLER ade ade badv

arch/loongarch/kernel/unwind_prologue.c

+88 −13
Original line number Diff line number Diff line
@@ -2,21 +2,101 @@ 
/*

 * Copyright (C) 2022 Loongson Technology Corporation Limited

 */

#include <linux/cpumask.h>

#include <linux/ftrace.h>

#include <linux/kallsyms.h>



#include <asm/inst.h>

#include <asm/loongson.h>

#include <asm/ptrace.h>

#include <asm/setup.h>

#include <asm/unwind.h>



static inline void unwind_state_fixup(struct unwind_state *state)

extern const int unwind_hint_ade;

extern const int unwind_hint_ale;

extern const int unwind_hint_bp;

extern const int unwind_hint_fpe;

extern const int unwind_hint_fpu;

extern const int unwind_hint_lsx;

extern const int unwind_hint_lasx;

extern const int unwind_hint_lbt;

extern const int unwind_hint_ri;

extern const int unwind_hint_watch;

extern unsigned long eentry;

#ifdef CONFIG_NUMA

extern unsigned long pcpu_handlers[NR_CPUS];

#endif



static inline bool scan_handlers(unsigned long entry_offset)

{

#ifdef CONFIG_DYNAMIC_FTRACE

	static unsigned long ftrace = (unsigned long)ftrace_call + 4;

	int idx, offset;



	if (entry_offset >= EXCCODE_INT_START * VECSIZE)

		return false;



	idx = entry_offset / VECSIZE;

	offset = entry_offset % VECSIZE;

	switch (idx) {

	case EXCCODE_ADE:

		return offset == unwind_hint_ade;

	case EXCCODE_ALE:

		return offset == unwind_hint_ale;

	case EXCCODE_BP:

		return offset == unwind_hint_bp;

	case EXCCODE_FPE:

		return offset == unwind_hint_fpe;

	case EXCCODE_FPDIS:

		return offset == unwind_hint_fpu;

	case EXCCODE_LSXDIS:

		return offset == unwind_hint_lsx;

	case EXCCODE_LASXDIS:

		return offset == unwind_hint_lasx;

	case EXCCODE_BTDIS:

		return offset == unwind_hint_lbt;

	case EXCCODE_INE:

		return offset == unwind_hint_ri;

	case EXCCODE_WATCH:

		return offset == unwind_hint_watch;

	default:

		return false;

	}

}



	if (state->pc == ftrace)

		state->is_ftrace = true;

static inline bool fix_exception(unsigned long pc)

{

#ifdef CONFIG_NUMA

	int cpu;



	for_each_possible_cpu(cpu) {

		if (!pcpu_handlers[cpu])

			continue;

		if (scan_handlers(pc - pcpu_handlers[cpu]))

			return true;

	}

#endif

	return scan_handlers(pc - eentry);

}



/*

 * As we meet ftrace_regs_entry, reset first flag like first doing

 * tracing. Prologue analysis will stop soon because PC is at entry.

 */

static inline bool fix_ftrace(unsigned long pc)

{

#ifdef CONFIG_DYNAMIC_FTRACE

	return pc == (unsigned long)ftrace_call + LOONGARCH_INSN_SIZE;

#else

	return false;

#endif

}



static inline bool unwind_state_fixup(struct unwind_state *state)

{

	if (!fix_exception(state->pc) && !fix_ftrace(state->pc))

		return false;



	state->reset = true;

	return true;

}



/*
@@ -39,14 +119,10 @@ static bool unwind_by_prologue(struct unwind_state *state) 
	if (state->sp >= info->end || state->sp < info->begin)

		return false;



	if (state->is_ftrace) {

		/*

		 * As we meet ftrace_regs_entry, reset first flag like first doing

		 * tracing. Prologue analysis will stop soon because PC is at entry.

		 */

	if (state->reset) {

		regs = (struct pt_regs *)state->sp;

		state->first = true;

		state->is_ftrace = false;

		state->reset = false;

		state->pc = regs->csr_era;

		state->ra = regs->regs[1];

		state->sp = regs->regs[3];
@@ -112,8 +188,7 @@ static bool unwind_by_prologue(struct unwind_state *state) 


out:

	state->first = false;

	unwind_state_fixup(state);

	return !!__kernel_text_address(state->pc);

	return unwind_state_fixup(state) || __kernel_text_address(state->pc);

}



static bool next_frame(struct unwind_state *state)

arch/loongarch/mm/tlb.c

+1 −1
Original line number Diff line number Diff line
@@ -251,7 +251,7 @@ static void output_pgtable_bits_defines(void) 
}



#ifdef CONFIG_NUMA

static unsigned long pcpu_handlers[NR_CPUS];

unsigned long pcpu_handlers[NR_CPUS];

#endif

extern long exception_handlers[VECSIZE * 128 / sizeof(long)];