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Subject[PATCH v3 3/4] LoongArch: Add stacktrace support
Date
Use common arch_stack_walk infrastructure to avoid duplicated code and
avoid taking care of the stack storage and filtering.
Add sra (means __schedule return address) and scfa (means __schedule call
frame address) to thread_info and store it in switch_to().

Now we can print the process stack by cat /proc/*/stack and can better
support ftrace.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
---
arch/loongarch/Kconfig | 5 ++++
arch/loongarch/include/asm/processor.h | 9 +++++++
arch/loongarch/include/asm/switch_to.h | 14 ++++++----
arch/loongarch/kernel/Makefile | 1 +
arch/loongarch/kernel/asm-offsets.c | 2 ++
arch/loongarch/kernel/process.c | 3 +++
arch/loongarch/kernel/stacktrace.c | 37 ++++++++++++++++++++++++++
arch/loongarch/kernel/switch.S | 2 ++
8 files changed, 68 insertions(+), 5 deletions(-)
create mode 100644 arch/loongarch/kernel/stacktrace.c

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 62b5b07fa4e1..85d0fa3147cd 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -38,6 +38,7 @@ config LOONGARCH
select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_MIGHT_HAVE_PC_SERIO
+ select ARCH_STACKWALK
select ARCH_SPARSEMEM_ENABLE
select ARCH_SUPPORTS_ACPI
select ARCH_SUPPORTS_ATOMIC_RMW
@@ -140,6 +141,10 @@ config LOCKDEP_SUPPORT
bool
default y

+config STACKTRACE_SUPPORT
+ bool
+ default y
+
# MACH_LOONGSON32 and MACH_LOONGSON64 are delibrately carried over from the
# MIPS Loongson code, to preserve Loongson-specific code paths in drivers that
# are shared between architectures, and specifically expecting the symbols.
diff --git a/arch/loongarch/include/asm/processor.h b/arch/loongarch/include/asm/processor.h
index 57ec45aa078e..1c4b4308378d 100644
--- a/arch/loongarch/include/asm/processor.h
+++ b/arch/loongarch/include/asm/processor.h
@@ -101,6 +101,10 @@ struct thread_struct {
unsigned long reg23, reg24, reg25, reg26; /* s0-s3 */
unsigned long reg27, reg28, reg29, reg30, reg31; /* s4-s8 */

+ /* __schedule() return address / call frame address */
+ unsigned long sched_ra;
+ unsigned long sched_cfa;
+
/* CSR registers */
unsigned long csr_prmd;
unsigned long csr_crmd;
@@ -129,6 +133,9 @@ struct thread_struct {
struct loongarch_fpu fpu FPU_ALIGN;
};

+#define thread_saved_ra(tsk) (tsk->thread.sched_ra)
+#define thread_saved_fp(tsk) (tsk->thread.sched_cfa)
+
#define INIT_THREAD { \
/* \
* Main processor registers \
@@ -145,6 +152,8 @@ struct thread_struct {
.reg29 = 0, \
.reg30 = 0, \
.reg31 = 0, \
+ .sched_ra = 0, \
+ .sched_cfa = 0, \
.csr_crmd = 0, \
.csr_prmd = 0, \
.csr_euen = 0, \
diff --git a/arch/loongarch/include/asm/switch_to.h b/arch/loongarch/include/asm/switch_to.h
index 2a8d04375574..43a5ab162d38 100644
--- a/arch/loongarch/include/asm/switch_to.h
+++ b/arch/loongarch/include/asm/switch_to.h
@@ -15,12 +15,15 @@ struct task_struct;
* @prev: The task previously executed.
* @next: The task to begin executing.
* @next_ti: task_thread_info(next).
+ * @sched_ra: __schedule return address.
+ * @sched_cfa: __schedule call frame address.
*
* This function is used whilst scheduling to save the context of prev & load
* the context of next. Returns prev.
*/
extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
- struct task_struct *next, struct thread_info *next_ti);
+ struct task_struct *next, struct thread_info *next_ti,
+ void *sched_ra, void *sched_cfa);

/*
* For newly created kernel threads switch_to() will return to
@@ -28,10 +31,11 @@ extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
* That is, everything following __switch_to() will be skipped for new threads.
* So everything that matters to new threads should be placed before __switch_to().
*/
-#define switch_to(prev, next, last) \
-do { \
- lose_fpu_inatomic(1, prev); \
- (last) = __switch_to(prev, next, task_thread_info(next)); \
+#define switch_to(prev, next, last) \
+do { \
+ lose_fpu_inatomic(1, prev); \
+ (last) = __switch_to(prev, next, task_thread_info(next), \
+ __builtin_return_address(0), __builtin_frame_address(0)); \
} while (0)

#endif /* _ASM_SWITCH_TO_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 918600e7b30f..7449513eb08d 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_EFI) += efi.o
obj-$(CONFIG_CPU_HAS_FPU) += fpu.o

obj-$(CONFIG_MODULES) += module.o module-sections.o
+obj-$(CONFIG_STACKTRACE) += stacktrace.o

obj-$(CONFIG_PROC_FS) += proc.o

diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
index 20cd9e16a95a..eb350f3ffae5 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -103,6 +103,8 @@ void output_thread_defines(void)
OFFSET(THREAD_REG29, task_struct, thread.reg29);
OFFSET(THREAD_REG30, task_struct, thread.reg30);
OFFSET(THREAD_REG31, task_struct, thread.reg31);
+ OFFSET(THREAD_SCHED_RA, task_struct, thread.sched_ra);
+ OFFSET(THREAD_SCHED_CFA, task_struct, thread.sched_cfa);
OFFSET(THREAD_CSRCRMD, task_struct,
thread.csr_crmd);
OFFSET(THREAD_CSRPRMD, task_struct,
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 709b7a1664f8..34c3f2148714 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -135,6 +135,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
childregs = (struct pt_regs *) childksp - 1;
/* Put the stack after the struct pt_regs. */
childksp = (unsigned long) childregs;
+ p->thread.sched_cfa = 0;
p->thread.csr_euen = 0;
p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
@@ -145,6 +146,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
p->thread.reg23 = (unsigned long)args->fn;
p->thread.reg24 = (unsigned long)args->fn_arg;
p->thread.reg01 = (unsigned long)ret_from_kernel_thread;
+ p->thread.sched_ra = (unsigned long)ret_from_kernel_thread;
memset(childregs, 0, sizeof(struct pt_regs));
childregs->csr_euen = p->thread.csr_euen;
childregs->csr_crmd = p->thread.csr_crmd;
@@ -161,6 +163,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)

p->thread.reg03 = (unsigned long) childregs;
p->thread.reg01 = (unsigned long) ret_from_fork;
+ p->thread.sched_ra = (unsigned long) ret_from_fork;

/*
* New tasks lose permission to use the fpu. This accelerates context
diff --git a/arch/loongarch/kernel/stacktrace.c b/arch/loongarch/kernel/stacktrace.c
new file mode 100644
index 000000000000..f4f4b8ad3917
--- /dev/null
+++ b/arch/loongarch/kernel/stacktrace.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Stack trace management functions
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+#include <asm/stacktrace.h>
+#include <asm/unwind.h>
+
+void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+ struct task_struct *task, struct pt_regs *regs)
+{
+ struct pt_regs dummyregs;
+ struct unwind_state state;
+ unsigned long addr;
+
+ regs = &dummyregs;
+
+ if (task == current) {
+ regs->csr_era = (unsigned long)__builtin_return_address(0);
+ regs->regs[3] = (unsigned long)__builtin_frame_address(0);
+ } else {
+ regs->csr_era = thread_saved_ra(task);
+ regs->regs[3] = thread_saved_fp(task);
+ }
+
+ regs->regs[1] = 0;
+ for (unwind_start(&state, task, regs);
+ !unwind_done(&state); unwind_next_frame(&state)) {
+ addr = unwind_get_return_address(&state);
+ if (!addr || !consume_entry(cookie, addr))
+ break;
+ }
+}
diff --git a/arch/loongarch/kernel/switch.S b/arch/loongarch/kernel/switch.S
index 37e84ac8ffc2..43ebbc3990f7 100644
--- a/arch/loongarch/kernel/switch.S
+++ b/arch/loongarch/kernel/switch.S
@@ -21,6 +21,8 @@ SYM_FUNC_START(__switch_to)

cpu_save_nonscratch a0
stptr.d ra, a0, THREAD_REG01
+ stptr.d a3, a0, THREAD_SCHED_RA
+ stptr.d a4, a0, THREAD_SCHED_CFA
move tp, a2
cpu_restore_nonscratch a1

--
2.20.1
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