[PATCH 6.7 106/162] riscv: add CALLER_ADDRx support

Greg Kroah-Hartman
2024-03-04T21:30:29Z

From: Zong Li <zong.li@sifive.com>

commit 680341382da56bd192ebfa4e58eaf4fec2e5bca7 upstream.

CALLER_ADDRx returns caller's address at specified level, they are used
for several tracers. These macros eventually use
__builtin_return_address(n) to get the caller's address if arch doesn't
define their own implementation.

In RISC-V, __builtin_return_address(n) only works when n == 0, we need
to walk the stack frame to get the caller's address at specified level.

data.level started from 'level + 3' due to the call flow of getting
caller's address in RISC-V implementation. If we don't have additional
three iteration, the level is corresponding to follows:

callsite -> return_address -> arch_stack_walk -> walk_stackframe
| | | |
level 3 level 2 level 1 level 0

Fixes: 10626c32e382 ("riscv/ftrace: Add basic support")
Cc: stable@vger.kernel.org
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Link: https://lore.kernel.org/r/20240202015102.26251-1-zong.li@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/riscv/include/asm/ftrace.h | 5 +++
arch/riscv/kernel/Makefile | 2 +
arch/riscv/kernel/return_address.c | 48 +++++++++++++++++++++++++++++++++++++
3 files changed, 55 insertions(+)
create mode 100644 arch/riscv/kernel/return_address.c

--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -25,6 +25,11 @@

#define ARCH_SUPPORTS_FTRACE_OPS 1
#ifndef __ASSEMBLY__
+
+extern void *return_address(unsigned int level);
+
+#define ftrace_return_address(n) return_address(n)
+
void MCOUNT_NAME(void);
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -7,6 +7,7 @@ ifdef CONFIG_FTRACE
CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_patch.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_sbi.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE)
endif
CFLAGS_syscall_table.o += $(call cc-option,-Wno-override-init,)
CFLAGS_compat_syscall_table.o += $(call cc-option,-Wno-override-init,)
@@ -46,6 +47,7 @@ obj-y += irq.o
obj-y += process.o
obj-y += ptrace.o
obj-y += reset.o
+obj-y += return_address.o
obj-y += setup.o
obj-y += signal.o
obj-y += syscall_table.o
--- /dev/null
+++ b/arch/riscv/kernel/return_address.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This code come from arch/arm64/kernel/return_address.c
+ *
+ * Copyright (C) 2023 SiFive.
+ */
+
+#include <linux/export.h>
+#include <linux/kprobes.h>
+#include <linux/stacktrace.h>
+
+struct return_address_data {
+ unsigned int level;
+ void *addr;
+};
+
+static bool save_return_addr(void *d, unsigned long pc)
+{
+ struct return_address_data *data = d;
+
+ if (!data->level) {
+ data->addr = (void *)pc;
+ return false;
+ }
+
+ --data->level;
+
+ return true;
+}
+NOKPROBE_SYMBOL(save_return_addr);
+
+noinline void *return_address(unsigned int level)
+{
+ struct return_address_data data;
+
+ data.level = level + 3;
+ data.addr = NULL;
+
+ arch_stack_walk(save_return_addr, &data, current, NULL);
+
+ if (!data.level)
+ return data.addr;
+ else
+ return NULL;
+
+}
+EXPORT_SYMBOL_GPL(return_address);
+NOKPROBE_SYMBOL(return_address);