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// SPDX-License-Identifier: GPL-2.0-only
/*
* Stack tracing support
*
* Copyright (C) 2012 ARM Ltd.
*/
#include <linux/kernel.h>
#include <linux/efi.h>
#include <linux/export.h>
#include <linux/ftrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
#include <asm/efi.h>
#include <asm/irq.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>
/*
* Start an unwind from a pt_regs.
*
* The unwind will begin at the PC within the regs.
*
* The regs must be on a stack currently owned by the calling task.
*/
static __always_inline void
unwind_init_from_regs(struct unwind_state *state,
struct pt_regs *regs)
{
unwind_init_common(state, current);
state->fp = regs->regs[29];
state->pc = regs->pc;
}
/*
* Start an unwind from a caller.
*
* The unwind will begin at the caller of whichever function this is inlined
* into.
*
* The function which invokes this must be noinline.
*/
static __always_inline void
unwind_init_from_caller(struct unwind_state *state)
{
unwind_init_common(state, current);
state->fp = (unsigned long)__builtin_frame_address(1);
state->pc = (unsigned long)__builtin_return_address(0);
}
/*
* Start an unwind from a blocked task.
*
* The unwind will begin at the blocked tasks saved PC (i.e. the caller of
* cpu_switch_to()).
*
* The caller should ensure the task is blocked in cpu_switch_to() for the
* duration of the unwind, or the unwind will be bogus. It is never valid to
* call this for the current task.
*/
static __always_inline void
unwind_init_from_task(struct unwind_state *state,
struct task_struct *task)
{
unwind_init_common(state, task);
state->fp = thread_saved_fp(task);
state->pc = thread_saved_pc(task);
}
static __always_inline int
unwind_recover_return_address(struct unwind_state *state)
{
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
if (state->task->ret_stack &&
(state->pc == (unsigned long)return_to_handler)) {
unsigned long orig_pc;
orig_pc = ftrace_graph_ret_addr(state->task, NULL, state->pc,
(void *)state->fp);
if (WARN_ON_ONCE(state->pc == orig_pc))
return -EINVAL;
state->pc = orig_pc;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#ifdef CONFIG_KRETPROBES
if (is_kretprobe_trampoline(state->pc)) {
state->pc = kretprobe_find_ret_addr(state->task,
(void *)state->fp,
&state->kr_cur);
}
#endif /* CONFIG_KRETPROBES */
return 0;
}
/*
* Unwind from one frame record (A) to the next frame record (B).
*
* We terminate early if the location of B indicates a malformed chain of frame
* records (e.g. a cycle), determined based on the location and fp value of A
* and the location (but not the fp value) of B.
*/
static __always_inline int
unwind_next(struct unwind_state *state)
{
struct task_struct *tsk = state->task;
unsigned long fp = state->fp;
int err;
/* Final frame; nothing to unwind */
if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
return -ENOENT;
err = unwind_next_frame_record(state);
if (err)
return err;
state->pc = ptrauth_strip_kernel_insn_pac(state->pc);
return unwind_recover_return_address(state);
}
static __always_inline void
unwind(struct unwind_state *state, stack_trace_consume_fn consume_entry,
void *cookie)
{
if (unwind_recover_return_address(state))
return;
while (1) {
int ret;
if (!consume_entry(cookie, state->pc))
break;
ret = unwind_next(state);
if (ret < 0)
break;
}
}
/*
* Per-cpu stacks are only accessible when unwinding the current task in a
* non-preemptible context.
*/
#define STACKINFO_CPU(name) \
({ \
((task == current) && !preemptible()) \
? stackinfo_get_##name() \
: stackinfo_get_unknown(); \
})
/*
* SDEI stacks are only accessible when unwinding the current task in an NMI
* context.
*/
#define STACKINFO_SDEI(name) \
({ \
((task == current) && in_nmi()) \
? stackinfo_get_sdei_##name() \
: stackinfo_get_unknown(); \
})
#define STACKINFO_EFI \
({ \
((task == current) && current_in_efi()) \
? stackinfo_get_efi() \
: stackinfo_get_unknown(); \
})
noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
void *cookie, struct task_struct *task,
struct pt_regs *regs)
{
struct stack_info stacks[] = {
stackinfo_get_task(task),
STACKINFO_CPU(irq),
#if defined(CONFIG_VMAP_STACK)
STACKINFO_CPU(overflow),
#endif
#if defined(CONFIG_VMAP_STACK) && defined(CONFIG_ARM_SDE_INTERFACE)
STACKINFO_SDEI(normal),
STACKINFO_SDEI(critical),
#endif
#ifdef CONFIG_EFI
STACKINFO_EFI,
#endif
};
struct unwind_state state = {
.stacks = stacks,
.nr_stacks = ARRAY_SIZE(stacks),
};
if (regs) {
if (task != current)
return;
unwind_init_from_regs(&state, regs);
} else if (task == current) {
unwind_init_from_caller(&state);
} else {
unwind_init_from_task(&state, task);
}
unwind(&state, consume_entry, cookie);
}
static bool dump_backtrace_entry(void *arg, unsigned long where)
{
char *loglvl = arg;
printk("%s %pSb\n", loglvl, (void *)where);
return true;
}
void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
const char *loglvl)
{
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (regs && user_mode(regs))
return;
if (!tsk)
tsk = current;
if (!try_get_task_stack(tsk))
return;
printk("%sCall trace:\n", loglvl);
arch_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs);
put_task_stack(tsk);
}
void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
{
dump_backtrace(NULL, tsk, loglvl);
barrier();
}
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