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/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/interrupt.h>
#include <asm/sections.h>
#include <asm/ptrace.h>
#include <asm/bitops.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>
unsigned long unwind_get_return_address(struct unwind_state *state)
{
if (unwind_done(state))
return 0;
return __kernel_text_address(state->ip) ? state->ip : 0;
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);
static bool outside_of_stack(struct unwind_state *state, unsigned long sp)
{
return (sp <= state->sp) ||
(sp > state->stack_info.end - sizeof(struct stack_frame));
}
static bool update_stack_info(struct unwind_state *state, unsigned long sp)
{
struct stack_info *info = &state->stack_info;
unsigned long *mask = &state->stack_mask;
/* New stack pointer leaves the current stack */
if (get_stack_info(sp, state->task, info, mask) != 0 ||
!on_stack(info, sp, sizeof(struct stack_frame)))
/* 'sp' does not point to a valid stack */
return false;
return true;
}
static inline bool is_final_pt_regs(struct unwind_state *state,
struct pt_regs *regs)
{
/* user mode or kernel thread pt_regs at the bottom of task stack */
if (task_pt_regs(state->task) == regs)
return true;
/* user mode pt_regs at the bottom of irq stack */
return state->stack_info.type == STACK_TYPE_IRQ &&
state->stack_info.end - sizeof(struct pt_regs) == (unsigned long)regs &&
READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE;
}
/* Avoid KMSAN false positives from touching uninitialized frames. */
__no_kmsan_checks
bool unwind_next_frame(struct unwind_state *state)
{
struct stack_info *info = &state->stack_info;
struct stack_frame *sf;
struct pt_regs *regs;
unsigned long sp, ip;
bool reliable;
regs = state->regs;
if (unlikely(regs)) {
sp = state->sp;
sf = (struct stack_frame *) sp;
ip = READ_ONCE_NOCHECK(sf->gprs[8]);
reliable = false;
regs = NULL;
/* skip bogus %r14 or if is the same as regs->psw.addr */
if (!__kernel_text_address(ip) || state->ip == unwind_recover_ret_addr(state, ip)) {
state->regs = NULL;
return unwind_next_frame(state);
}
} else {
sf = (struct stack_frame *) state->sp;
sp = READ_ONCE_NOCHECK(sf->back_chain);
if (likely(sp)) {
/* Non-zero back-chain points to the previous frame */
if (unlikely(outside_of_stack(state, sp))) {
if (!update_stack_info(state, sp))
goto out_err;
}
sf = (struct stack_frame *) sp;
ip = READ_ONCE_NOCHECK(sf->gprs[8]);
reliable = true;
} else {
/* No back-chain, look for a pt_regs structure */
sp = state->sp + STACK_FRAME_OVERHEAD;
if (!on_stack(info, sp, sizeof(struct pt_regs)))
goto out_err;
regs = (struct pt_regs *) sp;
if (is_final_pt_regs(state, regs))
goto out_stop;
ip = READ_ONCE_NOCHECK(regs->psw.addr);
sp = READ_ONCE_NOCHECK(regs->gprs[15]);
if (unlikely(outside_of_stack(state, sp))) {
if (!update_stack_info(state, sp))
goto out_err;
}
reliable = true;
}
}
/* Sanity check: ABI requires SP to be aligned 8 bytes. */
if (sp & 0x7)
goto out_err;
/* Update unwind state */
state->sp = sp;
state->regs = regs;
state->reliable = reliable;
state->ip = unwind_recover_ret_addr(state, ip);
return true;
out_err:
state->error = true;
out_stop:
state->stack_info.type = STACK_TYPE_UNKNOWN;
return false;
}
EXPORT_SYMBOL_GPL(unwind_next_frame);
/* Avoid KMSAN false positives from touching uninitialized frames. */
__no_kmsan_checks
void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long first_frame)
{
struct stack_info *info = &state->stack_info;
struct stack_frame *sf;
unsigned long ip, sp;
memset(state, 0, sizeof(*state));
state->task = task;
state->regs = regs;
/* Don't even attempt to start from user mode regs: */
if (regs && user_mode(regs)) {
info->type = STACK_TYPE_UNKNOWN;
return;
}
/* Get the instruction pointer from pt_regs or the stack frame */
if (regs) {
ip = regs->psw.addr;
sp = regs->gprs[15];
} else if (task == current) {
sp = current_frame_address();
} else {
sp = task->thread.ksp;
}
/* Get current stack pointer and initialize stack info */
if (!update_stack_info(state, sp)) {
/* Something is wrong with the stack pointer */
info->type = STACK_TYPE_UNKNOWN;
state->error = true;
return;
}
if (!regs) {
/* Stack frame is within valid stack */
sf = (struct stack_frame *)sp;
ip = READ_ONCE_NOCHECK(sf->gprs[8]);
}
/* Update unwind state */
state->sp = sp;
state->reliable = true;
state->ip = unwind_recover_ret_addr(state, ip);
if (!first_frame)
return;
/* Skip through the call chain to the specified starting frame */
while (!unwind_done(state)) {
if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) {
if (state->sp >= first_frame)
break;
}
unwind_next_frame(state);
}
}
EXPORT_SYMBOL_GPL(__unwind_start);
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