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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2022 Loongson Technology Corporation Limited
*/
#include <linux/ftrace.h>
#include <linux/kallsyms.h>
#include <asm/inst.h>
#include <asm/ptrace.h>
#include <asm/unwind.h>
static inline void unwind_state_fixup(struct unwind_state *state)
{
#ifdef CONFIG_DYNAMIC_FTRACE
static unsigned long ftrace = (unsigned long)ftrace_call + 4;
if (state->pc == ftrace)
state->is_ftrace = true;
#endif
}
unsigned long unwind_get_return_address(struct unwind_state *state)
{
if (unwind_done(state))
return 0;
return state->pc;
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);
static bool unwind_by_guess(struct unwind_state *state)
{
struct stack_info *info = &state->stack_info;
unsigned long addr;
for (state->sp += sizeof(unsigned long);
state->sp < info->end;
state->sp += sizeof(unsigned long)) {
addr = *(unsigned long *)(state->sp);
state->pc = unwind_graph_addr(state, addr, state->sp + 8);
if (__kernel_text_address(state->pc))
return true;
}
return false;
}
static bool unwind_by_prologue(struct unwind_state *state)
{
long frame_ra = -1;
unsigned long frame_size = 0;
unsigned long size, offset, pc;
struct pt_regs *regs;
struct stack_info *info = &state->stack_info;
union loongarch_instruction *ip, *ip_end;
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.
*/
regs = (struct pt_regs *)state->sp;
state->first = true;
state->is_ftrace = false;
state->pc = regs->csr_era;
state->ra = regs->regs[1];
state->sp = regs->regs[3];
return true;
}
/*
* When first is not set, the PC is a return address in the previous frame.
* We need to adjust its value in case overflow to the next symbol.
*/
pc = state->pc - (state->first ? 0 : LOONGARCH_INSN_SIZE);
if (!kallsyms_lookup_size_offset(pc, &size, &offset))
return false;
ip = (union loongarch_instruction *)(pc - offset);
ip_end = (union loongarch_instruction *)pc;
while (ip < ip_end) {
if (is_stack_alloc_ins(ip)) {
frame_size = (1 << 12) - ip->reg2i12_format.immediate;
ip++;
break;
}
ip++;
}
if (!frame_size) {
if (state->first)
goto first;
return false;
}
while (ip < ip_end) {
if (is_ra_save_ins(ip)) {
frame_ra = ip->reg2i12_format.immediate;
break;
}
if (is_branch_ins(ip))
break;
ip++;
}
if (frame_ra < 0) {
if (state->first) {
state->sp = state->sp + frame_size;
goto first;
}
return false;
}
if (state->first)
state->first = false;
state->pc = *(unsigned long *)(state->sp + frame_ra);
state->sp = state->sp + frame_size;
goto out;
first:
state->first = false;
if (state->pc == state->ra)
return false;
state->pc = state->ra;
out:
unwind_state_fixup(state);
return !!__kernel_text_address(state->pc);
}
void unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs)
{
memset(state, 0, sizeof(*state));
state->type = UNWINDER_PROLOGUE;
if (regs) {
state->sp = regs->regs[3];
state->pc = regs->csr_era;
state->ra = regs->regs[1];
if (!__kernel_text_address(state->pc))
state->type = UNWINDER_GUESS;
} else if (task && task != current) {
state->sp = thread_saved_fp(task);
state->pc = thread_saved_ra(task);
state->ra = 0;
} else {
state->sp = (unsigned long)__builtin_frame_address(0);
state->pc = (unsigned long)__builtin_return_address(0);
state->ra = 0;
}
state->task = task;
state->first = true;
state->pc = unwind_graph_addr(state, state->pc, state->sp);
get_stack_info(state->sp, state->task, &state->stack_info);
if (!unwind_done(state) && !__kernel_text_address(state->pc))
unwind_next_frame(state);
}
EXPORT_SYMBOL_GPL(unwind_start);
bool unwind_next_frame(struct unwind_state *state)
{
struct stack_info *info = &state->stack_info;
struct pt_regs *regs;
unsigned long pc;
if (unwind_done(state))
return false;
do {
switch (state->type) {
case UNWINDER_GUESS:
state->first = false;
if (unwind_by_guess(state))
return true;
break;
case UNWINDER_PROLOGUE:
if (unwind_by_prologue(state)) {
state->pc = unwind_graph_addr(state, state->pc, state->sp);
return true;
}
if (info->type == STACK_TYPE_IRQ &&
info->end == state->sp) {
regs = (struct pt_regs *)info->next_sp;
pc = regs->csr_era;
if (user_mode(regs) || !__kernel_text_address(pc))
return false;
state->first = true;
state->ra = regs->regs[1];
state->sp = regs->regs[3];
state->pc = pc;
get_stack_info(state->sp, state->task, info);
return true;
}
}
state->sp = info->next_sp;
} while (!get_stack_info(state->sp, state->task, info));
return false;
}
EXPORT_SYMBOL_GPL(unwind_next_frame);
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