Re: [PATCH] riscv: add CALLER_ADDRx support
From: Alexandre Ghiti
Date: Wed Jan 31 2024 - 09:46:44 EST
Hi Zong,
On 31/01/2024 15:24, Zong Li wrote:
On Thu, Jan 18, 2024 at 8:50 AM Zong Li <zong.li@xxxxxxxxxx> wrote:
On Wed, Jan 10, 2024 at 11:33 AM Zong Li <zong.li@xxxxxxxxxx> wrote:
On Fri, Dec 29, 2023 at 2:34 PM Zong Li <zong.li@xxxxxxxxxx> wrote:
On Tue, Dec 5, 2023 at 5:00 PM Zong Li <zong.li@xxxxxxxxxx> wrote:
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
Signed-off-by: Zong Li <zong.li@xxxxxxxxxx>
---
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
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 2b2f5df7ef2c..42777f91a9c5 100644
--- 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 fee22a3d1b53..40d054939ae2 100644
--- 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
index 000000000000..c2008d4aa6e5
--- /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);
+
+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);
--
2.17.1
Hi Palmer and all,
I was wondering whether this patch is good for everyone? Thanks
Hi Palmer,
Is there any chance to include this patch in 6.8-rc1? Thanks
Hi Palmer,
I'm not sure if this patch is a feature or bug fix, would you consider
it for 6.8-rcX? Thanks
Hi Palmer,
Sorry for pinging you again. I'm not sure if you saw this patch. The
irqsoff and wakeup tracer will use CALLER_ADDR1 and CALLER_ADDR2 to
obtain the caller's return address, but we are currently encountering
an issue in the RISC-V port where the wrong caller is identified. I
guess you can easily reproduce the situation using ftrace. Could you
share your thoughts on this when you have the time to take a look?
Thanks
I'm not Palmer but I'll take a look at your patch today :)
Thanks,
Alex
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