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| author | Palmer Dabbelt <palmer@rivosinc.com> | 2023-02-15 19:57:13 +0100 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2023-02-15 19:59:54 +0100 |
| commit | ec6311919ea616be69076d03c3e2d2f7769d5f5f (patch) | |
| tree | cd6255ac7e95d6786ac4ebdae7ac8a1cb62d5efe /arch/riscv/Makefile | |
| parent | Merge patch series "Remove toolchain dependencies for Zicbom" (diff) | |
| parent | riscv: ftrace: Reduce the detour code size to half (diff) | |
| download | linux-ec6311919ea616be69076d03c3e2d2f7769d5f5f.tar.xz linux-ec6311919ea616be69076d03c3e2d2f7769d5f5f.zip | |
Merge patch series "riscv: Optimize function trace"
guoren@kernel.org <guoren@kernel.org> says:
From: Guo Ren <guoren@linux.alibaba.com>
The previous ftrace detour implementation fc76b8b8011 ("riscv: Using
PATCHABLE_FUNCTION_ENTRY instead of MCOUNT") contain three problems.
- The most horrible bug is preemption panic which found by Andy [1].
Let's disable preemption for ftrace first, and Andy could continue
the ftrace preemption work.
- The "-fpatchable-function-entry= CFLAG" wasted code size
!RISCV_ISA_C.
- The ftrace detour implementation wasted code size.
- When livepatching, the trampoline (ftrace_regs_caller) would not
return to <func_prolog+12> but would rather jump to the new function.
So, "REG_L ra, -SZREG(sp)" would not run and the original return
address would not be restored. The kernel is likely to hang or crash
as a result. (Found by Evgenii Shatokhin [4])
[Palmer: The first three patches in this series are pretty concrete
fixes, so I'm pulling them ahead of the rest of the series.]
* b4-shazam-merge:
riscv: ftrace: Reduce the detour code size to half
riscv: ftrace: Remove wasted nops for !RISCV_ISA_C
riscv: ftrace: Fixup panic by disabling preemption
Link: https://lore.kernel.org/r/20230112090603.1295340-1-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/Makefile')
| -rw-r--r-- | arch/riscv/Makefile | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index f9ba78ddb5c6..76989561566b 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -11,7 +11,11 @@ LDFLAGS_vmlinux := ifeq ($(CONFIG_DYNAMIC_FTRACE),y) LDFLAGS_vmlinux := --no-relax KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY - CC_FLAGS_FTRACE := -fpatchable-function-entry=8 +ifeq ($(CONFIG_RISCV_ISA_C),y) + CC_FLAGS_FTRACE := -fpatchable-function-entry=4 +else + CC_FLAGS_FTRACE := -fpatchable-function-entry=2 +endif endif ifeq ($(CONFIG_CMODEL_MEDLOW),y) |