Unverified Commit 0ff7c3b3 authored by Zong Li's avatar Zong Li Committed by Palmer Dabbelt
Browse files

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: default avatarZong Li <zong.li@sifive.com>
Reviewed-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent 5303df24

arch/riscv/kernel/ftrace.c

+13 −0
Original line number Diff line number Diff line
@@ -7,10 +7,23 @@ 


#include <linux/ftrace.h>

#include <linux/uaccess.h>

#include <linux/memory.h>

#include <asm/cacheflush.h>

#include <asm/patch.h>



#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)

{

arch/riscv/kernel/patch.c

+7 −6
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 


#include <linux/spinlock.h>

#include <linux/mm.h>

#include <linux/memory.h>

#include <linux/uaccess.h>

#include <linux/stop_machine.h>

#include <asm/kprobes.h>
@@ -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);

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