Currently, a call trace drops a process stack walk when a separate IRQ stack is used. It makes a call trace information much less useful when a system gets paniked in interrupt context.
This patch addresses the issue with the following schemes: - Store aborted stack frame data - Decide whether another stack walk is needed or not via current sp - Loosen the frame pointer upper bound condition Cc: AKASHI Takahiro <[email protected]> Cc: James Morse <[email protected]> Signed-off-by: Jungseok Lee <[email protected]> --- arch/arm64/include/asm/irq.h | 12 +++++++++++ arch/arm64/kernel/asm-offsets.c | 3 +++ arch/arm64/kernel/entry.S | 10 ++++++++-- arch/arm64/kernel/stacktrace.c | 22 ++++++++++++++++++++- arch/arm64/kernel/traps.c | 13 ++++++++++++ 5 files changed, 57 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h index 6ea82e8..e5904a1 100644 --- a/arch/arm64/include/asm/irq.h +++ b/arch/arm64/include/asm/irq.h @@ -2,13 +2,25 @@ #define __ASM_IRQ_H #include <linux/irqchip/arm-gic-acpi.h> +#include <asm/stacktrace.h> #include <asm-generic/irq.h> struct irq_stack { void *stack; + struct stackframe frame; }; +DECLARE_PER_CPU(struct irq_stack, irq_stacks); + +static inline bool in_irq_stack(unsigned int cpu) +{ + unsigned long high = (unsigned long)per_cpu(irq_stacks, cpu).stack; + + return (current_stack_pointer >= round_down(high, THREAD_SIZE)) && + current_stack_pointer < high; +} + struct pt_regs; extern void migrate_irqs(void); diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index b16e3cf..fbb52f2d 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -42,6 +42,9 @@ int main(void) DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_context)); BLANK(); DEFINE(IRQ_STACK, offsetof(struct irq_stack, stack)); + DEFINE(IRQ_FRAME_FP, offsetof(struct irq_stack, frame.fp)); + DEFINE(IRQ_FRAME_SP, offsetof(struct irq_stack, frame.sp)); + DEFINE(IRQ_FRAME_PC, offsetof(struct irq_stack, frame.pc)); BLANK(); DEFINE(S_X0, offsetof(struct pt_regs, regs[0])); DEFINE(S_X1, offsetof(struct pt_regs, regs[1])); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 6d4e8c5..650cc05 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -121,7 +121,8 @@ * x21 - aborted SP * x22 - aborted PC * x23 - aborted PSTATE - */ + * x29 - aborted FP + */ .endm .macro kernel_exit, el @@ -184,7 +185,12 @@ alternative_endif mov x23, sp and x23, x23, #~(THREAD_SIZE - 1) cmp x20, x23 // check irq re-enterance - mov x19, sp + beq 1f + str x29, [x19, #IRQ_FRAME_FP] + str x21, [x19, #IRQ_FRAME_SP] + str x22, [x19, #IRQ_FRAME_PC] + mov x29, x24 +1: mov x19, sp csel x23, x19, x24, eq // x24 = top of irq stack mov sp, x23 .endm diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 407991b..5124649 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -43,7 +43,27 @@ int notrace unwind_frame(struct stackframe *frame) low = frame->sp; high = ALIGN(low, THREAD_SIZE); - if (fp < low || fp > high - 0x18 || fp & 0xf) + /* + * A frame pointer would reach an upper bound if a prologue of the + * first function of call trace looks as follows: + * + * stp x29, x30, [sp,#-16]! + * mov x29, sp + * + * Thus, the upper bound is (top of stack - 0x20) with consideration + * of a 16-byte empty space in THREAD_START_SP. + * + * The value, 0x20, however, does not cover all cases as interrupts + * are handled using a separate stack. That is, a call trace can start + * from elx_irq exception vectors. The symbols could not be promoted + * to candidates for a stack trace under the restriction, 0x20. + * + * The scenario is handled without complexity as 1) considering + * (bottom of stack + THREAD_START_SP) as a dummy frame pointer, the + * content of which is 0, and 2) allowing the case, which changes + * the value to 0x10 from 0x20. + */ + if (fp < low || fp > high - 0x10 || fp & 0xf) return -EINVAL; frame->sp = fp + 0x10; diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index f93aae5..44b2f828 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,6 +146,8 @@ 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 int cpu = smp_processor_id(); + bool in_irq = in_irq_stack(cpu); pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); @@ -170,6 +172,10 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) } pr_emerg("Call trace:\n"); +repeat: + if (in_irq) + pr_emerg("<IRQ>\n"); + while (1) { unsigned long where = frame.pc; int ret; @@ -179,6 +185,13 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) break; dump_backtrace_entry(where, frame.sp); } + + if (in_irq) { + frame = per_cpu(irq_stacks, cpu).frame; + in_irq = false; + pr_emerg("<EOI>\n"); + goto repeat; + } } void show_stack(struct task_struct *tsk, unsigned long *sp) -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
