From 6ca445d8af0ed5950ebf899415fd6bfcd7d9d7a3 Mon Sep 17 00:00:00 2001 From: Alexandre Ghiti Date: Thu, 23 May 2024 13:51:34 +0200 Subject: riscv: Fix early ftrace nop patching MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 --- arch/riscv/include/asm/cacheflush.h | 6 ++++++ arch/riscv/kernel/ftrace.c | 3 +++ 2 files changed, 9 insertions(+) (limited to 'arch/riscv') diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h index dd8d07146116..ce79c558a4c8 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 4d14eadcd765..87cbd86576b2 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; } -- cgit v1.2.3