arm64: pass a task parameter to unwind_frame()

Function graph tracer modifies a return address (LR) in a stack frame
to hook a function's return. This will result in many useless entries
(return_to_handler) showing up in a call stack list.
We will fix this problem in a later patch ("arm64: ftrace: fix a stack
tracer's output under function graph tracer"). But since real return
addresses are saved in ret_stack[] array in struct task_struct,
unwind functions need to be notified of, in addition to a stack pointer
address, which task is being traced in order to find out real return
addresses.

This patch extends unwind functions' interfaces by adding an extra
argument of a pointer to task_struct.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Author: AKASHI Takahiro

arch/arm64/include/asm/stacktrace.h

@@ -16,14 +16,16 @@
 #ifndef __ASM_STACKTRACE_H
 #define __ASM_STACKTRACE_H
 
+struct task_struct;
+
 struct stackframe {
 	unsigned long fp;
 	unsigned long sp;
 	unsigned long pc;
 };
 
-extern int unwind_frame(struct stackframe *frame);
-extern void walk_stackframe(struct stackframe *frame,
+extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame);
+extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 			    int (*fn)(struct stackframe *, void *), void *data);
 
 #endif	/* __ASM_STACKTRACE_H */

arch/arm64/kernel/perf_callchain.c

@@ -165,7 +165,7 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry,
 	frame.sp = regs->sp;
 	frame.pc = regs->pc;
 
-	walk_stackframe(&frame, callchain_trace, entry);
+	walk_stackframe(current, &frame, callchain_trace, entry);
 }
 
 unsigned long perf_instruction_pointer(struct pt_regs *regs)

arch/arm64/kernel/process.c

@@ -348,7 +348,7 @@ unsigned long get_wchan(struct task_struct *p)
 	do {
 		if (frame.sp < stack_page ||
 		    frame.sp >= stack_page + THREAD_SIZE ||
-		    unwind_frame(&frame))
+		    unwind_frame(p, &frame))
 			return 0;
 		if (!in_sched_functions(frame.pc))
 			return frame.pc;

arch/arm64/kernel/return_address.c

@@ -44,7 +44,7 @@ void *return_address(unsigned int level)
 	frame.sp = current_stack_pointer;
 	frame.pc = (unsigned long)return_address; /* dummy */
 
-	walk_stackframe(&frame, save_return_addr, &data);
+	walk_stackframe(current, &frame, save_return_addr, &data);
 
 	if (!data.level)
 		return data.addr;

arch/arm64/kernel/stacktrace.c

@@ -36,7 +36,7 @@
  *	ldp	x29, x30, [sp]
  *	add	sp, sp, #0x10
  */
-int notrace unwind_frame(struct stackframe *frame)
+int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 {
 	unsigned long high, low;
 	unsigned long fp = frame->fp;
@@ -99,15 +99,15 @@ int notrace unwind_frame(struct stackframe *frame)
 	return 0;
 }
 
-void notrace walk_stackframe(struct stackframe *frame,
+void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 		     int (*fn)(struct stackframe *, void *), void *data)
 {
 	while (1) {
 		int ret;
 
 		if (fn(frame, data))
 			break;
-		ret = unwind_frame(frame);
+		ret = unwind_frame(tsk, frame);
 		if (ret < 0)
 			break;
 	}
@@ -159,7 +159,7 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 		frame.pc = (unsigned long)save_stack_trace_tsk;
 	}
 
-	walk_stackframe(&frame, save_trace, &data);
+	walk_stackframe(tsk, &frame, save_trace, &data);
 	if (trace->nr_entries < trace->max_entries)
 		trace->entries[trace->nr_entries++] = ULONG_MAX;
 }

arch/arm64/kernel/time.c

@@ -53,7 +53,7 @@ unsigned long profile_pc(struct pt_regs *regs)
 	frame.sp = regs->sp;
 	frame.pc = regs->pc;
 	do {
-		int ret = unwind_frame(&frame);
+		int ret = unwind_frame(NULL, &frame);
 		if (ret < 0)
 			return 0;
 	} while (in_lock_functions(frame.pc));

arch/arm64/kernel/traps.c

@@ -177,7 +177,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 		int ret;
 
 		dump_backtrace_entry(where);
-		ret = unwind_frame(&frame);
+		ret = unwind_frame(tsk, &frame);
 		if (ret < 0)
 			break;
 		stack = frame.sp;