After the text section be mask as non-writable, the ftrace have to
change the permission of text for dynamic patching the intructions.
Add ftrace_arch_code_modify_prepare and
ftrace_arch_code_modify_post_process to change permission.
Signed-off-by: Zong Li <[email protected]>
---
arch/riscv/kernel/ftrace.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index c40fdcdeb950..576df0807200 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -7,9 +7,27 @@
#include <linux/ftrace.h>
#include <linux/uaccess.h>
+#include <linux/memory.h>
+#include <asm/set_memory.h>
#include <asm/cacheflush.h>
#ifdef CONFIG_DYNAMIC_FTRACE
+int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
+{
+ mutex_lock(&text_mutex);
+ set_kernel_text_rw();
+ set_all_modules_text_rw();
+ return 0;
+}
+
+int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
+{
+ set_all_modules_text_ro();
+ set_kernel_text_ro();
+ mutex_unlock(&text_mutex);
+ return 0;
+}
+
static int ftrace_check_current_call(unsigned long hook_pos,
unsigned int *expected)
{
--
2.25.0
On Mon, 17 Feb 2020 00:32:23 PST (-0800), [email protected] wrote:
> After the text section be mask as non-writable, the ftrace have to
> change the permission of text for dynamic patching the intructions.
> Add ftrace_arch_code_modify_prepare and
> ftrace_arch_code_modify_post_process to change permission.
>
> Signed-off-by: Zong Li <[email protected]>
> ---
> arch/riscv/kernel/ftrace.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
> index c40fdcdeb950..576df0807200 100644
> --- a/arch/riscv/kernel/ftrace.c
> +++ b/arch/riscv/kernel/ftrace.c
> @@ -7,9 +7,27 @@
>
> #include <linux/ftrace.h>
> #include <linux/uaccess.h>
> +#include <linux/memory.h>
> +#include <asm/set_memory.h>
> #include <asm/cacheflush.h>
>
> #ifdef CONFIG_DYNAMIC_FTRACE
> +int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
> +{
> + mutex_lock(&text_mutex);
> + set_kernel_text_rw();
> + set_all_modules_text_rw();
> + return 0;
> +}
None of the other architectures are doing anything remotely like this in these
functions, despite many supporting STRICT_KERNEL_RWX. Having a function that
maps all text as RW seems super dangerous, as one stack attack means NX is
gone.
Looks like FIX_TEXT_POKE0 is the magic that makes the other ports work.
> +
> +int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
> +{
> + set_all_modules_text_ro();
> + set_kernel_text_ro();
> + mutex_unlock(&text_mutex);
> + return 0;
> +}
Presumably this needs a icache flush as well? Probably better to do so when
installing the instructions, though.
> +
> static int ftrace_check_current_call(unsigned long hook_pos,
> unsigned int *expected)
> {
Palmer Dabbelt <[email protected]> 於 2020年3月5日 週四 上午9:44寫道：
>
> On Mon, 17 Feb 2020 00:32:23 PST (-0800), [email protected] wrote:
> > After the text section be mask as non-writable, the ftrace have to
> > change the permission of text for dynamic patching the intructions.
> > Add ftrace_arch_code_modify_prepare and
> > ftrace_arch_code_modify_post_process to change permission.
> >
> > Signed-off-by: Zong Li <[email protected]>
> > ---
> > arch/riscv/kernel/ftrace.c | 18 ++++++++++++++++++
> > 1 file changed, 18 insertions(+)
> >
> > diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
> > index c40fdcdeb950..576df0807200 100644
> > --- a/arch/riscv/kernel/ftrace.c
> > +++ b/arch/riscv/kernel/ftrace.c
> > @@ -7,9 +7,27 @@
> >
> > #include <linux/ftrace.h>
> > #include <linux/uaccess.h>
> > +#include <linux/memory.h>
> > +#include <asm/set_memory.h>
> > #include <asm/cacheflush.h>
> >
> > #ifdef CONFIG_DYNAMIC_FTRACE
> > +int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
> > +{
> > + mutex_lock(&text_mutex);
> > + set_kernel_text_rw();
> > + set_all_modules_text_rw();
> > + return 0;
> > +}
>
> None of the other architectures are doing anything remotely like this in these
> functions, despite many supporting STRICT_KERNEL_RWX. Having a function that
> maps all text as RW seems super dangerous, as one stack attack means NX is
> gone.
>
> Looks like FIX_TEXT_POKE0 is the magic that makes the other ports work.
>
Your concern is right. Let me change the way.
> > +
> > +int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
> > +{
> > + set_all_modules_text_ro();
> > + set_kernel_text_ro();
> > + mutex_unlock(&text_mutex);
> > + return 0;
> > +}
>
> Presumably this needs a icache flush as well? Probably better to do so when
> installing the instructions, though.
>
Yes, I think I lost it. Thanks.
> > +
> > static int ftrace_check_current_call(unsigned long hook_pos,
> > unsigned int *expected)
> > {
>