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/*
* Stack tracing support
*
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/kernel.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/irq.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>
/*
* AArch64 PCS assigns the frame pointer to x29.
*
* A simple function prologue looks like this:
* sub sp, sp, #0x10
* stp x29, x30, [sp]
* mov x29, sp
*
* A simple function epilogue looks like this:
* mov sp, x29
* ldp x29, x30, [sp]
* add sp, sp, #0x10
*/
int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
{
unsigned long high, low;
unsigned long fp = frame->fp;
unsigned long irq_stack_ptr;
if (!tsk)
tsk = current;
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
*/
if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
else
irq_stack_ptr = 0;
low = frame->sp;
/* irq stacks are not THREAD_SIZE aligned */
if (on_irq_stack(frame->sp, raw_smp_processor_id()))
high = irq_stack_ptr;
else
high = ALIGN(low, THREAD_SIZE) - 0x20;
if (fp < low || fp > high || fp & 0xf)
return -EINVAL;
frame->sp = fp + 0x10;
frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
if (tsk->ret_stack &&
(frame->pc == (unsigned long)return_to_handler)) {
/*
* This is a case where function graph tracer has
* modified a return address (LR) in a stack frame
* to hook a function return.
* So replace it to an original value.
*/
frame->pc = tsk->ret_stack[frame->graph--].ret;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
/*
* Check whether we are going to walk through from interrupt stack
* to task stack.
* If we reach the end of the stack - and its an interrupt stack,
* unpack the dummy frame to find the original elr.
*
* Check the frame->fp we read from the bottom of the irq_stack,
* and the original task stack pointer are both in current->stack.
*/
if (frame->sp == irq_stack_ptr) {
struct pt_regs *irq_args;
unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
if (object_is_on_stack((void *)orig_sp) &&
object_is_on_stack((void *)frame->fp)) {
frame->sp = orig_sp;
/* orig_sp is the saved pt_regs, find the elr */
irq_args = (struct pt_regs *)orig_sp;
frame->pc = irq_args->pc;
} else {
/*
* This frame has a non-standard format, and we
* didn't fix it, because the data looked wrong.
* Refuse to output this frame.
*/
return -EINVAL;
}
}
return 0;
}
void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
int (*fn)(struct stackframe *, void *), void *data)
{
while (1) {
int ret;
if (fn(frame, data))
break;
ret = unwind_frame(tsk, frame);
if (ret < 0)
break;
}
}
#ifdef CONFIG_STACKTRACE
struct stack_trace_data {
struct stack_trace *trace;
unsigned int no_sched_functions;
unsigned int skip;
};
static int save_trace(struct stackframe *frame, void *d)
{
struct stack_trace_data *data = d;
struct stack_trace *trace = data->trace;
unsigned long addr = frame->pc;
if (data->no_sched_functions && in_sched_functions(addr))
return 0;
if (data->skip) {
data->skip--;
return 0;
}
trace->entries[trace->nr_entries++] = addr;
return trace->nr_entries >= trace->max_entries;
}
void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
struct stack_trace_data data;
struct stackframe frame;
data.trace = trace;
data.skip = trace->skip;
data.no_sched_functions = 0;
frame.fp = regs->regs[29];
frame.sp = regs->sp;
frame.pc = regs->pc;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
frame.graph = current->curr_ret_stack;
#endif
walk_stackframe(current, &frame, save_trace, &data);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
struct stack_trace_data data;
struct stackframe frame;
if (!try_get_task_stack(tsk))
return;
data.trace = trace;
data.skip = trace->skip;
if (tsk != current) {
data.no_sched_functions = 1;
frame.fp = thread_saved_fp(tsk);
frame.sp = thread_saved_sp(tsk);
frame.pc = thread_saved_pc(tsk);
} else {
data.no_sched_functions = 0;
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;
frame.pc = (unsigned long)save_stack_trace_tsk;
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
frame.graph = tsk->curr_ret_stack;
#endif
walk_stackframe(tsk, &frame, save_trace, &data);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
put_task_stack(tsk);
}
void save_stack_trace(struct stack_trace *trace)
{
save_stack_trace_tsk(current, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
#endif
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