Commit 132cd887 authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Will Deacon
Browse files

arm64: Modify stack trace and dump for use with irq_stack

This patch allows unwind_frame() to traverse from interrupt stack to task
stack correctly. It requires data from a dummy stack frame, created
during irq_stack_entry(), added by a later patch.

A similar approach is taken to modify dump_backtrace(), which expects to
find struct pt_regs underneath any call to functions marked __exception.
When on an irq_stack, the struct pt_regs is stored on the old task stack,
the location of which is stored in the dummy stack frame.
Reviewed-by: default avatarCatalin Marinas <>
Signed-off-by: default avatarAKASHI Takahiro <>
[james.morse: merged two patches, reworked for per_cpu irq_stacks, and
 no alignment guarantees, added irq_stack definitions]
Signed-off-by: default avatarJames Morse <>
Signed-off-by: default avatarWill Deacon <>
parent 6cdf9c7c
#ifndef __ASM_IRQ_H
#define __ASM_IRQ_H
#ifndef __ASSEMBLER__
#include <linux/percpu.h>
#include <asm-generic/irq.h>
#include <asm/thread_info.h>
struct pt_regs;
DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
* The highest address on the stack, and the first to be used. Used to
* find the dummy-stack frame put down by el?_irq() in entry.S.
#define IRQ_STACK_PTR(cpu) ((unsigned long)per_cpu(irq_stack, cpu) + IRQ_STACK_START_SP)
* The offset from irq_stack_ptr where entry.S will store the original
* stack pointer. Used by unwind_frame() and dump_backtrace().
#define IRQ_STACK_TO_TASK_STACK(ptr) *((unsigned long *)(ptr - 0x10));
extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
static inline int nr_legacy_irqs(void)
......@@ -12,4 +34,14 @@ static inline int nr_legacy_irqs(void)
return 0;
static inline bool on_irq_stack(unsigned long sp, int cpu)
/* variable names the same as kernel/stacktrace.c */
unsigned long low = (unsigned long)per_cpu(irq_stack, cpu);
unsigned long high = low + IRQ_STACK_START_SP;
return (low <= sp && sp <= high);
#endif /* !__ASSEMBLER__ */
......@@ -30,6 +30,9 @@
unsigned long irq_err_count;
/* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned */
DEFINE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack) __aligned(16);
int arch_show_interrupts(struct seq_file *p, int prec)
show_ipi_list(p, prec);
......@@ -20,6 +20,7 @@
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <asm/irq.h>
#include <asm/stacktrace.h>
......@@ -39,17 +40,41 @@ int notrace unwind_frame(struct stackframe *frame)
unsigned long high, low;
unsigned long fp = frame->fp;
unsigned long irq_stack_ptr;
* Use raw_smp_processor_id() to avoid false-positives from
* CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping
* task stacks, we can be pre-empted in this case, so
* {raw_,}smp_processor_id() may give us the wrong value. Sleeping
* tasks can't ever be on an interrupt stack, so regardless of cpu,
* the checks will always fail.
irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
low = frame->sp;
high = ALIGN(low, THREAD_SIZE);
/* irq stacks are not THREAD_SIZE aligned */
if (on_irq_stack(frame->sp, raw_smp_processor_id()))
high = irq_stack_ptr;
high = ALIGN(low, THREAD_SIZE) - 0x20;
if (fp < low || fp > high - 0x18 || fp & 0xf)
if (fp < low || fp > high || fp & 0xf)
return -EINVAL;
frame->sp = fp + 0x10;
frame->fp = *(unsigned long *)(fp);
frame->pc = *(unsigned long *)(fp + 8);
* 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,
* read the original task stack pointer from the dummy frame.
if (frame->sp == irq_stack_ptr)
frame->sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
return 0;
......@@ -146,6 +146,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
struct stackframe frame;
unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
......@@ -180,9 +181,20 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
if (ret < 0)
stack = frame.sp;
if (in_exception_text(where))
if (in_exception_text(where)) {
* If we switched to the irq_stack before calling this
* exception handler, then the pt_regs will be on the
* task stack. The easiest way to tell is if the large
* pt_regs would overlap with the end of the irq_stack.
if (stack < irq_stack_ptr &&
(stack + sizeof(struct pt_regs)) > irq_stack_ptr)
stack = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
dump_mem("", "Exception stack", stack,
stack + sizeof(struct pt_regs), false);
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