riscv: add CALLER_ADDRx support

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>

diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 3291721229523456247532009bc2ed2ddc444540..15055f9df4daa1e4250c8a37c64193bf5c943ee3 100644 (file)
--- 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)
 {

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index f71910718053d841a361fd97e7d62da4f86bebcf..604d6bf7e47672e9b01902f6fa497aeb4e102ee5 100644 (file)
--- 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

diff --git a/arch/riscv/kernel/return_address.c b/arch/riscv/kernel/return_address.c
new file mode 100644 (file)
index 0000000..c8115ec
--- /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);