Adding an extra dummy stack frame for interrupt has one side-effect that
dump_backtrace() shows inccorect data of struct pt_regs at
"Exception stack ..." because we are still on an interrupt stack when
dump_backtrace() encounters an interrupt handler's frame.
This patch reuses __in_irqentry_text() macro, which was added by
commit 9a5ad7d0e3e1 ("arm64: Add __exception_irq_entry definition for
function graph"),
and allows dump_backtrace() to recognize an interrupt handler's
frame and fetch a correct pointer (sp) to struct pt_regs on an process
stack.
One of drawbacks in this approach is that we will sometimes see
__irqentry_text_start and gic_handle_irq interchangeably, especially,
when "perf report --call-graph" shows stack traces because both symbols
has the same address.
(Please note that this can happen even without this patch if
CONFIG_FUNCTION_GRAPH_TRACER is enabled.)
Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
---
arch/arm64/include/asm/exception.h | 7 +++----
arch/arm64/include/asm/traps.h | 7 -------
arch/arm64/kernel/traps.c | 9 +++++++--
arch/arm64/kernel/vmlinux.lds.S | 7 +++++++
4 files changed, 17 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/include/asm/exception.h
b/arch/arm64/include/asm/exception.h
index 6cb7e1a..8415005 100644
--- a/arch/arm64/include/asm/exception.h
+++ b/arch/arm64/include/asm/exception.h
@@ -21,10 +21,9 @@
#include <linux/ftrace.h>
#define __exception __attribute__((section(".exception.text")))
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/* We always need this definition for dump_backtrace */
+#undef __irq_entry
+#define __irq_entry __attribute__((__section__(".irqentry.text")))
#define __exception_irq_entry __irq_entry
-#else
-#define __exception_irq_entry __exception
-#endif
#endif /* __ASM_EXCEPTION_H */
diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
index 0cc2f29..8f05d3b 100644
--- a/arch/arm64/include/asm/traps.h
+++ b/arch/arm64/include/asm/traps.h
@@ -34,7 +34,6 @@ struct undef_hook {
void register_undef_hook(struct undef_hook *hook);
void unregister_undef_hook(struct undef_hook *hook);
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static inline int __in_irqentry_text(unsigned long ptr)
{
extern char __irqentry_text_start[];
@@ -43,12 +42,6 @@ static inline int __in_irqentry_text(unsigned long ptr)
return ptr >= (unsigned long)&__irqentry_text_start &&
ptr < (unsigned long)&__irqentry_text_end;
}
-#else
-static inline int __in_irqentry_text(unsigned long ptr)
-{
- return 0;
-}
-#endif
static inline int in_exception_text(unsigned long ptr)
{
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index e9b9b53..8fc3d4b 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -179,10 +179,15 @@ static void dump_backtrace(struct pt_regs *regs, struct
task_struct *tsk)
ret = unwind_frame(&frame);
if (ret < 0)
break;
- stack = frame.sp;
- if (in_exception_text(where))
+ if (__in_irqentry_text(where)) {
+ stack = *(unsigned long *)(frame.fp + 0x18);
+ dump_mem("", "Interrupt stack", stack,
+ stack + sizeof(struct pt_regs), false);
+ } else if (in_exception_text(where)) {
+ stack = frame.sp;
dump_mem("", "Exception stack", stack,
stack + sizeof(struct pt_regs), false);
+ }
}
}
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 9807333..0d16d02 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -44,6 +44,13 @@ jiffies = jiffies_64;
*(.idmap.text) \
VMLINUX_SYMBOL(__idmap_text_end) = .;
+#undef IRQENTRY_TEXT
+#define IRQENTRY_TEXT \
+ ALIGN_FUNCTION(); \
+ VMLINUX_SYMBOL(__irqentry_text_start) = .; \
+ *(.irqentry.text) \
+ VMLINUX_SYMBOL(__irqentry_text_end) = .;
+
/*
* The size of the PE/COFF section that covers the kernel image, which
* runs from stext to _edata, must be a round multiple of the PE/COFF
--
1.7.9.5
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