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")
Reviewed-by: Alexandre Ghiti <[email protected]>
Signed-off-by: Zong Li <[email protected]>
---
Changed in v2:
- Rebase to v6.8-rc2
- Add noinline attribute for return_address()
- Add a fixes tag
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 329172122952..15055f9df4da 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 f71910718053..604d6bf7e476 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..c8115ec8fb30
--- /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);
--
2.17.1
On Fri, Feb 2, 2024 at 9:51 AM Zong Li <[email protected]> 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
>
> Fixes: 10626c32e382 ("riscv/ftrace: Add basic support")
>
> Reviewed-by: Alexandre Ghiti <[email protected]>
> Signed-off-by: Zong Li <[email protected]>
> ---
>
> Changed in v2:
> - Rebase to v6.8-rc2
> - Add noinline attribute for return_address()
> - Add a fixes tag
>
> 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 329172122952..15055f9df4da 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 f71910718053..604d6bf7e476 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..c8115ec8fb30
> --- /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);
> --
> 2.17.1
>
Hi all,
Is there anything that can be improved in this patch? Thanks.
On Thu, 01 Feb 2024 17:51:02 PST (-0800), [email protected] 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
>
> Fixes: 10626c32e382 ("riscv/ftrace: Add basic support")
You've got a spurious newline here. I've got this queued up for
testing with that cleaned up, it should show up on fixes soon (assuming
it passes the tests and such).
>
> Reviewed-by: Alexandre Ghiti <[email protected]>
> Signed-off-by: Zong Li <[email protected]>
> ---
>
> Changed in v2:
> - Rebase to v6.8-rc2
> - Add noinline attribute for return_address()
> - Add a fixes tag
>
> 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 329172122952..15055f9df4da 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 f71910718053..604d6bf7e476 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..c8115ec8fb30
> --- /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);
Hello:
This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <[email protected]>:
On Fri, 2 Feb 2024 01:51:02 +0000 you 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.
>
> [...]
Here is the summary with links:
- [v2] riscv: add CALLER_ADDRx support
https://git.kernel.org/riscv/c/680341382da5
You are awesome, thank you!
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