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Subject[PATCH v4 3/9] riscv: patch code by fixmap mapping
Date
On strict kernel memory permission, the ftrace have to change the
permission of text for dynamic patching the intructions. Use
riscv_patch_text_nosync() to patch code instead of probe_kernel_write.

Signed-off-by: Zong Li <zong.li@sifive.com>
Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/riscv/kernel/ftrace.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index c40fdcdeb950..08396614d6f4 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -7,9 +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)
{
@@ -46,20 +60,14 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
{
unsigned int call[2];
unsigned int nops[2] = {NOP4, NOP4};
- int ret = 0;

make_call(hook_pos, target, call);

- /* replace the auipc-jalr pair at once */
- ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
- MCOUNT_INSN_SIZE);
- /* return must be -EPERM on write error */
- if (ret)
+ /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
+ if (patch_text_nosync
+ ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
return -EPERM;

- smp_mb();
- flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE);
-
return 0;
}

--
2.26.0
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