diff options
| author | Andy Chiu <andy.chiu@sifive.com> | 2023-01-12 04:05:57 -0500 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2023-02-15 10:58:09 -0800 |
| commit | 8547649981e6631328cd64f583667501ae385531 (patch) | |
| tree | 327b9f30e2d7c8daaca266e351f69662aa0cb576 /arch/riscv/Kconfig | |
| parent | 1b929c02afd37871d5afb9d498426f83432e71c2 (diff) | |
riscv: ftrace: Fixup panic by disabling preemption
In RISCV, we must use an AUIPC + JALR pair to encode an immediate,
forming a jump that jumps to an address over 4K. This may cause errors
if we want to enable kernel preemption and remove dependency from
patching code with stop_machine(). For example, if a task was switched
out on auipc. And, if we changed the ftrace function before it was
switched back, then it would jump to an address that has updated 11:0
bits mixing with previous XLEN:12 part.
p: patched area performed by dynamic ftrace
ftrace_prologue:
p| REG_S ra, -SZREG(sp)
p| auipc ra, 0x? ------------> preempted
...
change ftrace function
...
p| jalr -?(ra) <------------- switched back
p| REG_L ra, -SZREG(sp)
func:
xxx
ret
Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT")
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20230112090603.1295340-2-guoren@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/Kconfig')
| -rw-r--r-- | arch/riscv/Kconfig | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index e2b656043abf..ee0d39b26794 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -138,7 +138,7 @@ config RISCV select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER - select HAVE_FUNCTION_TRACER if !XIP_KERNEL + select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION config ARCH_MMAP_RND_BITS_MIN default 18 if 64BIT |