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SubjectRe: [PATCH v4 3/9] riscv: patch code by fixmap mapping
On Tue,  7 Apr 2020 22:46:48 +0800
Zong Li <zong.li@sifive.com> wrote:

> 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>

Looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks!

> ---
> 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
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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