From: Ruan Jinjie ruanjinjie@huawei.com
[ Upstream commit 99a670b2069c725a7b50318aa681d9cae8f89325 ]
On riscv qemu platform, when add kprobe event on do_sys_open() to show filename string arg, it just print fault as follow:
echo 'p:myprobe do_sys_open dfd=$arg1 filename=+0($arg2):string flags=$arg3 mode=$arg4' > kprobe_events
bash-166 [000] ...1. 360.195367: myprobe: (do_sys_open+0x0/0x84) dfd=0xffffffffffffff9c filename=(fault) flags=0x8241 mode=0x1b6
bash-166 [000] ...1. 360.219369: myprobe: (do_sys_open+0x0/0x84) dfd=0xffffffffffffff9c filename=(fault) flags=0x8241 mode=0x1b6
bash-191 [000] ...1. 360.378827: myprobe: (do_sys_open+0x0/0x84) dfd=0xffffffffffffff9c filename=(fault) flags=0x98800 mode=0x0
As riscv do not select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE, the +0($arg2) addr is processed as a kernel address though it is a userspace address, cause the above filename=(fault) print. So select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE to avoid the issue, after that the kprobe trace is ok as below:
bash-166 [000] ...1. 96.767641: myprobe: (do_sys_open+0x0/0x84) dfd=0xffffffffffffff9c filename="/dev/null" flags=0x8241 mode=0x1b6
bash-166 [000] ...1. 96.793751: myprobe: (do_sys_open+0x0/0x84) dfd=0xffffffffffffff9c filename="/dev/null" flags=0x8241 mode=0x1b6
bash-177 [000] ...1. 96.962354: myprobe: (do_sys_open+0x0/0x84) dfd=0xffffffffffffff9c filename="/sys/kernel/debug/tracing/events/kprobes/" flags=0x98800 mode=0x0
Signed-off-by: Ruan Jinjie ruanjinjie@huawei.com Acked-by: Björn Töpel bjorn@rivosinc.com Fixes: 0ebeea8ca8a4 ("bpf: Restrict bpf_probe_read{, str}() only to archs where they work") Link: https://lore.kernel.org/r/20230504072910.3742842-1-ruanjinjie@huawei.com Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/Kconfig | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 06b9b2f60b9fb..a85bbe28dcf46 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -25,6 +25,7 @@ config RISCV select ARCH_HAS_GIGANTIC_PAGE select ARCH_HAS_KCOV select ARCH_HAS_MMIOWB + select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_SET_DIRECT_MAP if MMU select ARCH_HAS_SET_MEMORY if MMU