diff options
| author | Martin Kaiser <martin@kaiser.cx> | 2025-12-23 14:50:06 +0100 |
|---|---|---|
| committer | Paul Walmsley <pjw@kernel.org> | 2026-01-07 13:25:56 -0700 |
| commit | b0d7f5f0c9f05f1b6d4ee7110f15bef9c11f9df0 (patch) | |
| tree | 4fca374bb2a3328819704721379961fe42e4e809 /arch | |
| parent | 957afeb99b111b672b3529a737fe19b95daaf1a2 (diff) | |
riscv: trace: fix snapshot deadlock with sbi ecall
If sbi_ecall.c's functions are traceable,
echo "__sbi_ecall:snapshot" > /sys/kernel/tracing/set_ftrace_filter
may get the kernel into a deadlock.
(Functions in sbi_ecall.c are excluded from tracing if
CONFIG_RISCV_ALTERNATIVE_EARLY is set.)
__sbi_ecall triggers a snapshot of the ringbuffer. The snapshot code
raises an IPI interrupt, which results in another call to __sbi_ecall
and another snapshot...
All it takes to get into this endless loop is one initial __sbi_ecall.
On RISC-V systems without SSTC extension, the clock events in
timer-riscv.c issue periodic sbi ecalls, making the problem easy to
trigger.
Always exclude the sbi_ecall.c functions from tracing to fix the
potential deadlock.
sbi ecalls can easiliy be logged via trace events, excluding ecall
functions from function tracing is not a big limitation.
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://patch.msgid.link/20251223135043.1336524-1-martin@kaiser.cx
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/riscv/kernel/Makefile | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index f60fce69b725..a01f6439d62b 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -3,12 +3,6 @@ # Makefile for the RISC-V Linux kernel # -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-disable-warning, override-init) CFLAGS_compat_syscall_table.o += $(call cc-disable-warning, override-init) @@ -24,7 +18,6 @@ CFLAGS_sbi_ecall.o := -mcmodel=medany ifdef CONFIG_FTRACE CFLAGS_REMOVE_alternative.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_cpufeature.o = $(CC_FLAGS_FTRACE) -CFLAGS_REMOVE_sbi_ecall.o = $(CC_FLAGS_FTRACE) endif ifdef CONFIG_RELOCATABLE CFLAGS_alternative.o += -fno-pie @@ -43,6 +36,14 @@ CFLAGS_sbi_ecall.o += -D__NO_FORTIFY endif endif +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) +CFLAGS_REMOVE_sbi_ecall.o = $(CC_FLAGS_FTRACE) +endif + always-$(KBUILD_BUILTIN) += vmlinux.lds obj-y += head.o |