From: Alexandre Ghiti Date: Thu, 23 May 2024 11:51:34 +0000 (+0200) Subject: riscv: Fix early ftrace nop patching X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=6ca445d8af0ed5950ebf899415fd6bfcd7d9d7a3;p=linux.git riscv: Fix early ftrace nop patching Commit c97bf629963e ("riscv: Fix text patching when IPI are used") converted ftrace_make_nop() to use patch_insn_write() which does not emit any icache flush relying entirely on __ftrace_modify_code() to do that. But we missed that ftrace_make_nop() was called very early directly when converting mcount calls into nops (actually on riscv it converts 2B nops emitted by the compiler into 4B nops). This caused crashes on multiple HW as reported by Conor and Björn since the booting core could have half-patched instructions in its icache which would trigger an illegal instruction trap: fix this by emitting a local flush icache when early patching nops. Fixes: c97bf629963e ("riscv: Fix text patching when IPI are used") Signed-off-by: Alexandre Ghiti Reported-by: Conor Dooley Tested-by: Conor Dooley Reviewed-by: Björn Töpel Tested-by: Björn Töpel Link: https://lore.kernel.org/r/20240523115134.70380-1-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt --- diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h index dd8d07146116c..ce79c558a4c85 100644 --- a/arch/riscv/include/asm/cacheflush.h +++ b/arch/riscv/include/asm/cacheflush.h @@ -13,6 +13,12 @@ static inline void local_flush_icache_all(void) asm volatile ("fence.i" ::: "memory"); } +static inline void local_flush_icache_range(unsigned long start, + unsigned long end) +{ + local_flush_icache_all(); +} + #define PG_dcache_clean PG_arch_1 static inline void flush_dcache_folio(struct folio *folio) diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index 4d14eadcd7651..87cbd86576b28 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -120,6 +120,9 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) out = ftrace_make_nop(mod, rec, MCOUNT_ADDR); mutex_unlock(&text_mutex); + if (!mod) + local_flush_icache_range(rec->ip, rec->ip + MCOUNT_INSN_SIZE); + return out; }