[PATCH 3/3] arm: Modify stack trace and dump for use with irq stack
From: Maninder Singh
Date: Thu Oct 08 2020 - 03:17:52 EST
This patch allows unwind_frame() to traverse from interrupt stack to task
stack correctly.
A similar approach is taken to modify dump_backtrace_entry(),
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.
c_backtrace() is also modified on same logic, when traversing from last
IRQ frame, update fp with SVC mode fp.
Co-developed-by: Vaneet Narang <v.narang@xxxxxxxxxxx>
Signed-off-by: Vaneet Narang <v.narang@xxxxxxxxxxx>
Signed-off-by: Maninder Singh <maninder1.s@xxxxxxxxxxx>
---
arch/arm/include/asm/irq.h | 7 +++++++
arch/arm/kernel/stacktrace.c | 21 ++++++++++++++++++++
arch/arm/kernel/traps.c | 47 +++++++++++++++++++++++++++++++++++++++++---
arch/arm/lib/backtrace.S | 18 +++++++++++++++++
4 files changed, 90 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index f3299ab..d4c66e9 100644
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -30,6 +30,13 @@
#ifdef CONFIG_IRQ_STACK
DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
+
+#define IRQ_STACK_BASE_PTR (unsigned long)(raw_cpu_read(irq_stack_ptr))
+#define IRQ_STACK_TOP_PTR (unsigned long)(raw_cpu_read(irq_stack_ptr) + IRQ_STACK_SIZE)
+
+#define IRQ_STACK_TO_TASK_FRAME(ptr) (*((unsigned long *)(ptr + 0x4)))
+#define IRQ_STACK_TO_TASK_STACK(ptr) (*((unsigned long *)(ptr + 0x8)))
+
#endif
extern void asm_do_IRQ(unsigned int, struct pt_regs *);
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 76ea417..65b9634 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -7,6 +7,9 @@
#include <asm/sections.h>
#include <asm/stacktrace.h>
#include <asm/traps.h>
+#ifdef CONFIG_IRQ_STACK
+#include <asm/irq.h>
+#endif
#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
/*
@@ -42,6 +45,13 @@ int notrace unwind_frame(struct stackframe *frame)
{
unsigned long high, low;
unsigned long fp = frame->fp;
+#ifdef CONFIG_IRQ_STACK
+ unsigned long irq_stack_base_p;
+ unsigned long irq_stack_p;
+
+ irq_stack_base_p = IRQ_STACK_BASE_PTR;
+ irq_stack_p = irq_stack_base_p + IRQ_STACK_SIZE;
+#endif
/* only go to a higher address on the stack */
low = frame->sp;
@@ -67,6 +77,17 @@ int notrace unwind_frame(struct stackframe *frame)
frame->pc = *(unsigned long *)(fp - 4);
#endif
+#ifdef CONFIG_IRQ_STACK
+ /*
+ * 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 base + 4 of IRQ stack.
+ */
+ if (frame->sp == irq_stack_p)
+ frame->sp = IRQ_STACK_TO_TASK_STACK(irq_stack_base_p);
+#endif
+
return 0;
}
#endif
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 17d5a78..36b0cda 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -65,8 +65,20 @@ static int __init user_debug_setup(char *str)
void dump_backtrace_entry(unsigned long where, unsigned long from,
unsigned long frame, const char *loglvl)
{
- unsigned long end = frame + 4 + sizeof(struct pt_regs);
+ unsigned long end;
+#ifdef CONFIG_IRQ_STACK
+ unsigned long irq_stack_base_p;
+ unsigned long irq_stack_p;
+
+ irq_stack_base_p = IRQ_STACK_BASE_PTR;
+ irq_stack_p = irq_stack_base_p + IRQ_STACK_SIZE;
+
+ if (frame < irq_stack_p && (frame + sizeof(struct pt_regs)) > irq_stack_p)
+ frame = IRQ_STACK_TO_TASK_STACK(irq_stack_base_p) - 4;
+#endif
+
+ end = frame + 4 + sizeof(struct pt_regs);
#ifdef CONFIG_KALLSYMS
printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
loglvl, where, (void *)where, from, (void *)from);
@@ -113,6 +125,35 @@ static int verify_stack(unsigned long sp)
return 0;
}
+
+#ifdef CONFIG_IRQ_STACK
+static int fp_underflow(unsigned long fp, struct task_struct *tsk)
+{
+ unsigned long end = (unsigned long)end_of_stack(tsk);
+ unsigned long irq_stack_base_p;
+ unsigned long irq_stack_p;
+
+ irq_stack_base_p = IRQ_STACK_BASE_PTR;
+ irq_stack_p = irq_stack_base_p + IRQ_STACK_SIZE;
+
+
+ if (fp > end && fp < end + THREAD_SIZE)
+ return 0;
+
+ if (fp > irq_stack_base_p && fp < irq_stack_p)
+ return 0;
+
+ return 1;
+}
+#else
+static int fp_underflow(unsigned long fp, struct task_struct *tsk)
+{
+ if (fp < (unsigned long)end_of_stack(tsk))
+ return 1;
+
+ return 0;
+}
+#endif
#endif
/*
@@ -238,7 +279,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
} else if (verify_stack(fp)) {
pr_cont("invalid frame pointer 0x%08x", fp);
ok = 0;
- } else if (fp < (unsigned long)end_of_stack(tsk))
+ } else if (fp_underflow(fp, tsk))
pr_cont("frame pointer underflow");
pr_cont("\n");
@@ -292,7 +333,7 @@ static int __die(const char *str, int err, struct pt_regs *regs)
if (!user_mode(regs) || in_interrupt()) {
dump_mem(KERN_EMERG, "Stack: ", regs->ARM_sp,
- THREAD_SIZE + (unsigned long)task_stack_page(tsk));
+ THREAD_SIZE + (unsigned long)(regs->ARM_sp & ~(THREAD_SIZE - 1)));
dump_backtrace(regs, tsk, KERN_EMERG);
dump_instr(KERN_EMERG, regs);
}
diff --git a/arch/arm/lib/backtrace.S b/arch/arm/lib/backtrace.S
index 872f658..1a8e645 100644
--- a/arch/arm/lib/backtrace.S
+++ b/arch/arm/lib/backtrace.S
@@ -9,6 +9,9 @@
#include <linux/kern_levels.h>
#include <linux/linkage.h>
#include <asm/assembler.h>
+#ifdef CONFIG_IRQ_STACK
+#include <asm/irq.h>
+#endif
.text
@ fp is 0 or stack frame
@@ -96,6 +99,21 @@ for_each_frame: tst frame, mask @ Check for address exceptions
teq sv_fp, #0 @ zero saved fp means
beq no_frame @ no further frames
+#ifdef CONFIG_IRQ_STACK
+ /*
+ * check if it is swtiching from IRQ to SVC,
+ * then update frame accordingly.
+ */
+ this_cpu_ptr irq_stack_ptr r2 r3
+ ldr r3, [r2]
+ add r2, r3, #IRQ_STACK_SIZE
+ ldr r0, [frame, #-8]
+ cmp r2, r0
+ ldreq sv_fp, [r3, #4]
+ moveq frame, sv_fp
+ beq for_each_frame
+#endif
+
cmp sv_fp, frame @ next frame must be
mov frame, sv_fp @ above the current frame
bhi for_each_frame
--
1.9.1