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Subject[PATCH v2 12/14] openrisc: support framepointers and STACKTRACE_SUPPORT
Date
For lockdep support a reliable stack trace mechanism is needed.  This
patch adds support in OpenRISC for the stacktrace framework, implemented
by a simple unwinder api. The unwinder api supports both framepointer
and basic stack tracing.

The unwinder is now used to replace the stack_dump() implementation as
well. The new traces are inline with other architectures trace format:

Call trace:
[<c0004448>] show_stack+0x3c/0x58
[<c031c940>] dump_stack+0xa8/0xe4
[<c0008104>] __cpu_up+0x64/0x130
[<c000d268>] bringup_cpu+0x3c/0x178
[<c000d038>] cpuhp_invoke_callback+0xa8/0x1fc
[<c000d680>] cpuhp_up_callbacks+0x44/0x14c
[<c000e400>] cpu_up+0x14c/0x1bc
[<c041da60>] smp_init+0x104/0x15c
[<c033843c>] ? kernel_init+0x0/0x140
[<c0415e04>] kernel_init_freeable+0xbc/0x25c
[<c033843c>] ? kernel_init+0x0/0x140
[<c0338458>] kernel_init+0x1c/0x140
[<c003a174>] ? schedule_tail+0x18/0xa0
[<c0006b80>] ret_from_fork+0x1c/0x9c

Signed-off-by: Stafford Horne <shorne@gmail.com>
---
arch/openrisc/Kconfig | 4 ++
arch/openrisc/include/asm/unwinder.h | 20 +++++++
arch/openrisc/kernel/Makefile | 3 +-
arch/openrisc/kernel/stacktrace.c | 86 ++++++++++++++++++++++++++++
arch/openrisc/kernel/traps.c | 54 +++---------------
arch/openrisc/kernel/unwinder.c | 105 +++++++++++++++++++++++++++++++++++
6 files changed, 224 insertions(+), 48 deletions(-)
create mode 100644 arch/openrisc/include/asm/unwinder.h
create mode 100644 arch/openrisc/kernel/stacktrace.c
create mode 100644 arch/openrisc/kernel/unwinder.c

diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index bfff04ae7f7d..399f55e82dcb 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -33,6 +33,7 @@ config OPENRISC
select ARCH_USE_QUEUED_SPINLOCKS
select ARCH_USE_QUEUED_RWLOCKS
select OMPIC if SMP
+ select ARCH_WANT_FRAME_POINTERS

config CPU_BIG_ENDIAN
def_bool y
@@ -60,6 +61,9 @@ config TRACE_IRQFLAGS_SUPPORT
config GENERIC_CSUM
def_bool y

+config STACKTRACE_SUPPORT
+ def_bool y
+
source "init/Kconfig"

source "kernel/Kconfig.freezer"
diff --git a/arch/openrisc/include/asm/unwinder.h b/arch/openrisc/include/asm/unwinder.h
new file mode 100644
index 000000000000..165ec6f02ab8
--- /dev/null
+++ b/arch/openrisc/include/asm/unwinder.h
@@ -0,0 +1,20 @@
+/*
+ * OpenRISC unwinder.h
+ *
+ * Architecture API for unwinding stacks.
+ *
+ * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#ifndef __ASM_OPENRISC_UNWINDER_H
+#define __ASM_OPENRISC_UNWINDER_H
+
+void unwind_stack(void *data, unsigned long *stack,
+ void (*trace)(void *data, unsigned long addr,
+ int reliable));
+
+#endif /* __ASM_OPENRISC_UNWINDER_H */
diff --git a/arch/openrisc/kernel/Makefile b/arch/openrisc/kernel/Makefile
index 7d94643c878d..b4b51a07016a 100644
--- a/arch/openrisc/kernel/Makefile
+++ b/arch/openrisc/kernel/Makefile
@@ -6,9 +6,10 @@ extra-y := head.o vmlinux.lds

obj-y := setup.o or32_ksyms.o process.o dma.o \
traps.o time.o irq.o entry.o ptrace.o signal.o \
- sys_call_table.o
+ sys_call_table.o unwinder.o

obj-$(CONFIG_SMP) += smp.o
+obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_OF) += prom.o

diff --git a/arch/openrisc/kernel/stacktrace.c b/arch/openrisc/kernel/stacktrace.c
new file mode 100644
index 000000000000..43f140a28bc7
--- /dev/null
+++ b/arch/openrisc/kernel/stacktrace.c
@@ -0,0 +1,86 @@
+/*
+ * Stack trace utility for OpenRISC
+ *
+ * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ *
+ * Losely based on work from sh and powerpc.
+ */
+
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/stacktrace.h>
+
+#include <asm/processor.h>
+#include <asm/unwinder.h>
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ */
+static void
+save_stack_address(void *data, unsigned long addr, int reliable)
+{
+ struct stack_trace *trace = data;
+
+ if (!reliable)
+ return;
+
+ if (trace->skip > 0) {
+ trace->skip--;
+ return;
+ }
+
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = addr;
+}
+
+void save_stack_trace(struct stack_trace *trace)
+{
+ unwind_stack(trace, (unsigned long *) &trace, save_stack_address);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+static void
+save_stack_address_nosched(void *data, unsigned long addr, int reliable)
+{
+ struct stack_trace *trace = (struct stack_trace *)data;
+
+ if (!reliable)
+ return;
+
+ if (in_sched_functions(addr))
+ return;
+
+ if (trace->skip > 0) {
+ trace->skip--;
+ return;
+ }
+
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = addr;
+}
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+ unsigned long *sp = NULL;
+
+ if (tsk == current)
+ sp = (unsigned long *) &sp;
+ else
+ sp = (unsigned long *) KSTK_ESP(tsk);
+
+ unwind_stack(trace, sp, save_stack_address_nosched);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+void
+save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
+{
+ unwind_stack(trace, (unsigned long *) regs->sp,
+ save_stack_address_nosched);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_regs);
diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index 803e9e756f77..4085d72fa5ae 100644
--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -38,6 +38,7 @@
#include <asm/segment.h>
#include <asm/io.h>
#include <asm/pgtable.h>
+#include <asm/unwinder.h>

extern char _etext, _stext;

@@ -45,61 +46,20 @@ int kstack_depth_to_print = 0x180;
int lwa_flag;
unsigned long __user *lwa_addr;

-static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
+void print_trace(void *data, unsigned long addr, int reliable)
{
- return p > (void *)tinfo && p < (void *)tinfo + THREAD_SIZE - 3;
-}
-
-void show_trace(struct task_struct *task, unsigned long *stack)
-{
- struct thread_info *context;
- unsigned long addr;
-
- context = (struct thread_info *)
- ((unsigned long)stack & (~(THREAD_SIZE - 1)));
-
- while (valid_stack_ptr(context, stack)) {
- addr = *stack++;
- if (__kernel_text_address(addr)) {
- printk(" [<%08lx>]", addr);
- print_symbol(" %s", addr);
- printk("\n");
- }
- }
- printk(" =======================\n");
+ pr_emerg("[<%p>] %s%pS\n", (void *) addr, reliable ? "" : "? ",
+ (void *) addr);
}

/* displays a short stack trace */
void show_stack(struct task_struct *task, unsigned long *esp)
{
- unsigned long addr, *stack;
- int i;
-
if (esp == NULL)
esp = (unsigned long *)&esp;

- stack = esp;
-
- printk("Stack dump [0x%08lx]:\n", (unsigned long)esp);
- for (i = 0; i < kstack_depth_to_print; i++) {
- if (kstack_end(stack))
- break;
- if (__get_user(addr, stack)) {
- /* This message matches "failing address" marked
- s390 in ksymoops, so lines containing it will
- not be filtered out by ksymoops. */
- printk("Failing address 0x%lx\n", (unsigned long)stack);
- break;
- }
- stack++;
-
- printk("sp + %02d: 0x%08lx\n", i * 4, addr);
- }
- printk("\n");
-
- show_trace(task, esp);
-
- return;
+ pr_emerg("Call trace:\n");
+ unwind_stack(NULL, esp, print_trace);
}

void show_trace_task(struct task_struct *tsk)
@@ -115,7 +75,7 @@ void show_registers(struct pt_regs *regs)
int in_kernel = 1;
unsigned long esp;

- esp = (unsigned long)(&regs->sp);
+ esp = (unsigned long)(regs->sp);
if (user_mode(regs))
in_kernel = 0;

diff --git a/arch/openrisc/kernel/unwinder.c b/arch/openrisc/kernel/unwinder.c
new file mode 100644
index 000000000000..8ae15c2c1845
--- /dev/null
+++ b/arch/openrisc/kernel/unwinder.c
@@ -0,0 +1,105 @@
+/*
+ * OpenRISC unwinder.c
+ *
+ * Reusable arch specific api for unwinding stacks.
+ *
+ * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#include <linux/sched/task_stack.h>
+#include <linux/kernel.h>
+
+#include <asm/unwinder.h>
+
+#ifdef CONFIG_FRAME_POINTER
+struct or1k_frameinfo {
+ unsigned long *fp;
+ unsigned long ra;
+ unsigned long top;
+};
+
+/*
+ * Verify a frameinfo structure. The return address should be a valid text
+ * address. The frame pointer may be null if its the last frame, otherwise
+ * the frame pointer should point to a location in the stack after the the
+ * top of the next frame up.
+ */
+static inline int or1k_frameinfo_valid(struct or1k_frameinfo *frameinfo)
+{
+ return (frameinfo->fp == NULL ||
+ (!kstack_end(frameinfo->fp) &&
+ frameinfo->fp > &frameinfo->top)) &&
+ __kernel_text_address(frameinfo->ra);
+}
+
+/*
+ * Create a stack trace doing scanning which is frame pointer aware. We can
+ * get reliable stack traces by matching the previously found frame
+ * pointer with the top of the stack address every time we find a valid
+ * or1k_frameinfo.
+ *
+ * Ideally the stack parameter will be passed as FP, but it can not be
+ * guaranteed. Therefore we scan each address looking for the first sign
+ * of a return address.
+ *
+ * The OpenRISC stack frame looks something like the following. The
+ * location SP is held in r1 and location FP is held in r2 when frame pointers
+ * enabled.
+ *
+ * SP -> (top of stack)
+ * - (callee saved registers)
+ * - (local variables)
+ * FP-8 -> previous FP \
+ * FP-4 -> return address |- or1k_frameinfo
+ * FP -> (previous top of stack) /
+ */
+void unwind_stack(void *data, unsigned long *stack,
+ void (*trace)(void *data, unsigned long addr, int reliable))
+{
+ unsigned long *next_fp = NULL;
+ struct or1k_frameinfo *frameinfo = NULL;
+ int reliable = 0;
+
+ while (!kstack_end(stack)) {
+ frameinfo = container_of(stack,
+ struct or1k_frameinfo,
+ top);
+
+ if (__kernel_text_address(frameinfo->ra)) {
+ if (or1k_frameinfo_valid(frameinfo) &&
+ (next_fp == NULL ||
+ next_fp == &frameinfo->top)) {
+ reliable = 1;
+ next_fp = frameinfo->fp;
+ } else
+ reliable = 0;
+
+ trace(data, frameinfo->ra, reliable);
+ }
+ stack++;
+ }
+}
+
+#else /* CONFIG_FRAME_POINTER */
+
+/*
+ * Create a stack trace by doing a simple scan treating all text addresses
+ * as return addresses.
+ */
+void unwind_stack(void *data, unsigned long *stack,
+ void (*trace)(void *data, unsigned long addr, int reliable))
+{
+ unsigned long addr;
+
+ while (!kstack_end(stack)) {
+ addr = *stack++;
+ if (__kernel_text_address(addr))
+ trace(data, addr, 0);
+ }
+}
+#endif /* CONFIG_FRAME_POINTER */
+
--
2.13.5
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