linux-kernel - [PATCH v2 8/9] LoongArch/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR

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Date:   Fri, 26 Aug 2022 15:36:25 +0800
From:   Qing Zhang <zhangqing@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Jiaxun Yang <jiaxun.yang@...goat.com>, hejinyang@...ngson.cn
Subject: [PATCH v2 8/9] LoongArch/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support

Ftrace_graph_ret_addr can be called by stack unwinding code to convert
a found stack return address ('ret') to its original value, in case the
function graph tracer has modified it to be 'return_to_handler',If the
hasn't been modified, the unchanged value of 'ret' is returned.

Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
---
 arch/loongarch/include/asm/ftrace.h     |  3 +++
 arch/loongarch/include/asm/unwind.h     |  1 +
 arch/loongarch/kernel/ftrace_dyn.c      |  2 +-
 arch/loongarch/kernel/unwind_guess.c    |  4 +++-
 arch/loongarch/kernel/unwind_prologue.c | 10 +++++++++-
 5 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
index ce119496c6d0..0c306f42a512 100644
--- a/arch/loongarch/include/asm/ftrace.h
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -10,6 +10,8 @@
 #define FTRACE_REGS_PLT_IDX	1
 #define NR_FTRACE_PLTS		2
 
+#define GRAPH_FAKE_OFFSET (sizeof(struct pt_regs) - offsetof(struct pt_regs, regs[1]))
+
 #ifdef CONFIG_FUNCTION_TRACER
 #define MCOUNT_INSN_SIZE 4		/* sizeof mcount call */
 
@@ -20,6 +22,7 @@ extern void _mcount(void);
 #endif
 
 #ifdef CONFIG_DYNAMIC_FTRACE
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
 	return addr;
diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
index 6af4718bdf01..f66b07c3e6a1 100644
--- a/arch/loongarch/include/asm/unwind.h
+++ b/arch/loongarch/include/asm/unwind.h
@@ -21,6 +21,7 @@ struct unwind_state {
 	struct stack_info stack_info;
 	struct task_struct *task;
 	bool first, error;
+	int graph_idx;
 	unsigned long sp, pc, ra;
 };
 
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
index dd37185d446e..b070ce225989 100644
--- a/arch/loongarch/kernel/ftrace_dyn.c
+++ b/arch/loongarch/kernel/ftrace_dyn.c
@@ -219,7 +219,7 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)
 
 	old = *parent;
 
-	if (!function_graph_enter(old, self_addr, 0, NULL))
+	if (!function_graph_enter(old, self_addr, 0, parent))
 		*parent = return_hooker;
 }
 
diff --git a/arch/loongarch/kernel/unwind_guess.c b/arch/loongarch/kernel/unwind_guess.c
index 5afa6064d73e..229ba014cea0 100644
--- a/arch/loongarch/kernel/unwind_guess.c
+++ b/arch/loongarch/kernel/unwind_guess.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2022 Loongson Technology Corporation Limited
  */
+#include <linux/ftrace.h>
 #include <linux/kernel.h>
 
 #include <asm/unwind.h>
@@ -53,7 +54,8 @@ bool unwind_next_frame(struct unwind_state *state)
 		     state->sp < info->end;
 		     state->sp += sizeof(unsigned long)) {
 			addr = *(unsigned long *)(state->sp);
-
+			state->pc = ftrace_graph_ret_addr(state->task, &state->graph_idx,
+				addr, (unsigned long *)(state->sp - GRAPH_FAKE_OFFSET));
 			if (__kernel_text_address(addr))
 				return true;
 		}
diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
index b206d9159205..03f8b31a90cc 100644
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2022 Loongson Technology Corporation Limited
  */
+#include <linux/ftrace.h>
 #include <linux/kallsyms.h>
 
 #include <asm/inst.h>
@@ -32,6 +33,8 @@ static bool unwind_by_guess(struct unwind_state *state)
 	     state->sp < info->end;
 	     state->sp += sizeof(unsigned long)) {
 		addr = *(unsigned long *)(state->sp);
+		state->pc = ftrace_graph_ret_addr(state->task, &state->graph_idx,
+			addr, (unsigned long *)(state->sp - GRAPH_FAKE_OFFSET));
 		if (__kernel_text_address(addr))
 			return true;
 	}
@@ -146,8 +149,11 @@ bool unwind_next_frame(struct unwind_state *state)
 			break;
 
 		case UNWINDER_PROLOGUE:
-			if (unwind_by_prologue(state))
+			if (unwind_by_prologue(state)) {
+				state->pc = ftrace_graph_ret_addr(state->task, &state->graph_idx,
+					state->pc, (unsigned long *)(state->sp - GRAPH_FAKE_OFFSET));
 				return true;
+			}
 
 			if (info->type == STACK_TYPE_IRQ &&
 				info->end == state->sp) {
@@ -159,6 +165,8 @@ bool unwind_next_frame(struct unwind_state *state)
 
 				state->pc = pc;
 				state->sp = regs->regs[3];
+				state->pc = ftrace_graph_ret_addr(state->task, &state->graph_idx,
+					pc, (unsigned long *)(state->sp - GRAPH_FAKE_OFFSET));
 				state->ra = regs->regs[1];
 				state->first = true;
 				get_stack_info(state->sp, state->task, info);
-- 
2.20.1