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Message-Id: <1444231692-32722-3-git-send-email-jungseoklee85@gmail.com>
Date: Wed, 7 Oct 2015 15:28:12 +0000
From: Jungseok Lee <jungseoklee85@...il.com>
To: catalin.marinas@....com, will.deacon@....com,
linux-arm-kernel@...ts.infradead.org
Cc: james.morse@....com, takahiro.akashi@...aro.org,
mark.rutland@....com, barami97@...il.com,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/2] arm64: Expand the stack trace feature to support IRQ stack
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 <takahiro.akashi@...aro.org>
Cc: James Morse <james.morse@....com>
Signed-off-by: Jungseok Lee <jungseoklee85@...il.com>
---
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
--
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