From 132cd887b5c54758d04bf25c52fa48f45e843a30 Mon Sep 17 00:00:00 2001 From: AKASHI Takahiro Date: Fri, 4 Dec 2015 11:02:26 +0000 Subject: [PATCH] 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: Catalin Marinas Signed-off-by: AKASHI Takahiro [james.morse: merged two patches, reworked for per_cpu irq_stacks, and no alignment guarantees, added irq_stack definitions] Signed-off-by: James Morse Signed-off-by: Will Deacon --- arch/arm64/include/asm/irq.h | 32 ++++++++++++++++++++++++++++++++ arch/arm64/kernel/irq.c | 3 +++ arch/arm64/kernel/stacktrace.c | 29 +++++++++++++++++++++++++++-- arch/arm64/kernel/traps.c | 14 +++++++++++++- 4 files changed, 75 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h index 8e8d306..e2f3f13 100644 --- a/arch/arm64/include/asm/irq.h +++ b/arch/arm64/include/asm/irq.h @@ -1,10 +1,32 @@ #ifndef __ASM_IRQ_H #define __ASM_IRQ_H +#define IRQ_STACK_SIZE THREAD_SIZE +#define IRQ_STACK_START_SP THREAD_START_SP + +#ifndef __ASSEMBLER__ + +#include + #include +#include 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__ */ #endif diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c index 9f17ec0..1e3cef5 100644 --- a/arch/arm64/kernel/irq.c +++ b/arch/arm64/kernel/irq.c @@ -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); diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index ccb6078..b947eef 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -20,6 +20,7 @@ #include #include +#include #include /* @@ -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; + else + 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; } diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index e9b9b53..8a00845 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -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) break; 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); + } } } -- 2.7.4