The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 8547649981e6631328cd64f583667501ae385531 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '167820471419475@xxxxxxxxx' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: 8547649981e6 ("riscv: ftrace: Fixup panic by disabling preemption") f32b4b467ebd ("RISC-V: enable dynamic ftrace for RV32I") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8547649981e6631328cd64f583667501ae385531 Mon Sep 17 00:00:00 2001 From: Andy Chiu <andy.chiu@xxxxxxxxxx> Date: Thu, 12 Jan 2023 04:05:57 -0500 Subject: [PATCH] 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@xxxxxxxxxx> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230112090603.1295340-2-guoren@xxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx> 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
