From 0ff7c3b331276f584bde3ae9a16bacd8fa3d01e6 Mon Sep 17 00:00:00 2001 From: Zong Li Date: Tue, 21 Apr 2020 15:30:01 +0800 Subject: [PATCH] riscv: Use text_mutex instead of patch_lock We don't need the additional lock protection when patching the text. There are two patching interfaces here: - patch_text: patch code and always synchronize with stop_machine() - patch_text_nosync: patch code without synchronization, it's caller's responsibility to synchronize all CPUs if needed. For the first one, stop_machine() is protected by its own mutex, and also the irq is already disabled here. For the second one, in risc-v real case now, it would be used to ftrace patching the mcount function, since it already running under kstop_machine(), no other thread will run, so we could use text_mutex on ftrace side. Signed-off-by: Zong Li Reviewed-by: Masami Hiramatsu Reviewed-by: Palmer Dabbelt Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/ftrace.c | 13 +++++++++++++ arch/riscv/kernel/patch.c | 13 +++++++------ 2 files changed, 20 insertions(+), 6 deletions(-) diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index fb1e2b8..0839661 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -7,10 +7,23 @@ #include #include +#include #include #include #ifdef CONFIG_DYNAMIC_FTRACE +int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex) +{ + mutex_lock(&text_mutex); + return 0; +} + +int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex) +{ + mutex_unlock(&text_mutex); + return 0; +} + static int ftrace_check_current_call(unsigned long hook_pos, unsigned int *expected) { diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 8acb9ae2..5805791c 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -18,8 +19,6 @@ struct patch_insn { }; #ifdef CONFIG_MMU -static DEFINE_RAW_SPINLOCK(patch_lock); - static void *patch_map(void *addr, int fixmap) { uintptr_t uintaddr = (uintptr_t) addr; @@ -49,10 +48,14 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) { void *waddr = addr; bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; - unsigned long flags = 0; int ret; - raw_spin_lock_irqsave(&patch_lock, flags); + /* + * Before reaching here, it was expected to lock the text_mutex + * already, so we don't need to give another lock here and could + * ensure that it was safe between each cores. + */ + lockdep_assert_held(&text_mutex); if (across_pages) patch_map(addr + len, FIX_TEXT_POKE1); @@ -66,8 +69,6 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) if (across_pages) patch_unmap(FIX_TEXT_POKE1); - raw_spin_unlock_irqrestore(&patch_lock, flags); - return ret; } NOKPROBE_SYMBOL(patch_insn_write); -- 2.7.4