6.6-stable review patch. If anyone has any objections, please let me know.
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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);