On Mon, Jun 24, 2024 at 7:49 PM Andy Chiu <andy.c...@sifive.com> wrote: > > Hi Alex, > > On Mon, Jun 24, 2024 at 4:21 PM Alexandre Ghiti <alexgh...@rivosinc.com> > wrote: > > > > We cannot delay the icache flush after patching some functions as we may > > have patched a function that will get called before the icache flush. > > > > The only way to completely avoid such scenario is by flushing the icache > > as soon as we patch a function. This will probably be costly as we don't > > batch the icache maintenance anymore. > > > > Fixes: 6ca445d8af0e ("riscv: Fix early ftrace nop patching") > > Reported-by: Conor Dooley <conor.doo...@microchip.com> > > Closes: > > https://lore.kernel.org/linux-riscv/20240613-lubricant-breath-061192a9489a@wendy/ > > Signed-off-by: Alexandre Ghiti <alexgh...@rivosinc.com>
Reviewed-by: Andy Chiu <andy.c...@sifive.com> > > --- > > arch/riscv/kernel/ftrace.c | 7 ++----- > > arch/riscv/kernel/patch.c | 26 ++++++++++++++++++-------- > > 2 files changed, 20 insertions(+), 13 deletions(-) > > > > diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c > > index 87cbd86576b2..4b95c574fd04 100644 > > --- a/arch/riscv/kernel/ftrace.c > > +++ b/arch/riscv/kernel/ftrace.c > > @@ -120,9 +120,6 @@ 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; > > } > > > > @@ -156,9 +153,9 @@ static int __ftrace_modify_code(void *data) > > } else { > > while (atomic_read(¶m->cpu_count) <= num_online_cpus()) > > cpu_relax(); > > - } > > > > - local_flush_icache_all(); > > + local_flush_icache_all(); > > + } > > Sorry, maybe I should point it out directly earlier. But I don't think > this diff chunk is required. Threads running in the else clause from > stop_machine must not run into any patchable entry. If it runs into a > patchable entry, running the local fence.i is not going to fix the > problem. Sorry, I read the code wrong. The local flush is not in the while loop. I have no problem with this chunk after properly seeing them. > > > > > return 0; > > } > > diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c > > index 4007563fb607..ab03732d06c4 100644 > > --- a/arch/riscv/kernel/patch.c > > +++ b/arch/riscv/kernel/patch.c > > @@ -89,6 +89,14 @@ static int __patch_insn_set(void *addr, u8 c, size_t len) > > > > memset(waddr, c, len); > > > > + /* > > + * We could have just patched a function that is about to be > > + * called so make sure we don't execute partially patched > > + * instructions by flushing the icache as soon as possible. > > + */ > > + local_flush_icache_range((unsigned long)waddr, > > + (unsigned long)waddr + len); > > + > > patch_unmap(FIX_TEXT_POKE0); > > > > if (across_pages) > > @@ -135,6 +143,14 @@ static int __patch_insn_write(void *addr, const void > > *insn, size_t len) > > > > ret = copy_to_kernel_nofault(waddr, insn, len); > > > > + /* > > + * We could have just patched a function that is about to be > > + * called so make sure we don't execute partially patched > > + * instructions by flushing the icache as soon as possible. > > + */ > > + local_flush_icache_range((unsigned long)waddr, > > + (unsigned long)waddr + len); > > + > > patch_unmap(FIX_TEXT_POKE0); > > > > if (across_pages) > > @@ -189,9 +205,6 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len) > > > > ret = patch_insn_set(tp, c, len); > > > > - if (!ret) > > - flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len); > > - > > return ret; > > } > > NOKPROBE_SYMBOL(patch_text_set_nosync); > > @@ -224,9 +237,6 @@ int patch_text_nosync(void *addr, const void *insns, > > size_t len) > > > > ret = patch_insn_write(tp, insns, len); > > > > - if (!ret) > > - flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len); > > - > > return ret; > > } > > NOKPROBE_SYMBOL(patch_text_nosync); > > @@ -253,9 +263,9 @@ static int patch_text_cb(void *data) > > } else { > > while (atomic_read(&patch->cpu_count) <= num_online_cpus()) > > cpu_relax(); > > - } > > > > - local_flush_icache_all(); > > + local_flush_icache_all(); > > + } > > > > return ret; > > } > > -- > > 2.39.2 > > > > Thanks, > Andy