Re: [PATCH 2/3] arm64: kprobes: Remove unneeded RODATA check

[James Morse]

Hi!

On 17/12/2018 06:41, Masami Hiramatsu wrote:
> Remove unneeded RODATA check from arch_prepare_kprobe().
> 
> Since check_kprobe_address_safe() already ensured that
> the probe address is in kernel text, we don't need to
> check whether the address in RODATA or not. That must
> be always false.

So it does!

Reviewed-by: James Morse 


Thanks

James

> diff --git a/arch/arm64/kernel/probes/kprobes.c 
> b/arch/arm64/kernel/probes/kprobes.c
> index b2d4b7428ebc..1dae500d0a81 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -91,8 +91,6 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, 
> struct pt_regs *regs)
>  int __kprobes arch_prepare_kprobe(struct kprobe *p)
>  {
>   unsigned long probe_addr = (unsigned long)p->addr;
> - extern char __start_rodata[];
> - extern char __end_rodata[];
>  
>   if (probe_addr & 0x3)
>   return -EINVAL;
> @@ -106,10 +104,6 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>   if (search_exception_tables(probe_addr))
>   return -EINVAL;
>  
> - if (probe_addr >= (unsigned long) __start_rodata &&
> - probe_addr <= (unsigned long) __end_rodata)
> - return -EINVAL;
> -
>   /* decode instruction */
>   switch (arm_kprobe_decode_insn(p->addr, >ainsn)) {
>   case INSN_REJECTED: /* insn not supported */
> 

[PATCH 2/3] arm64: kprobes: Remove unneeded RODATA check

[Masami Hiramatsu]

Remove unneeded RODATA check from arch_prepare_kprobe().

Since check_kprobe_address_safe() already ensured that
the probe address is in kernel text, we don't need to
check whether the address in RODATA or not. That must
be always false.

Signed-off-by: Masami Hiramatsu 
---
 arch/arm64/kernel/probes/kprobes.c |6 --
 1 file changed, 6 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c 
b/arch/arm64/kernel/probes/kprobes.c
index b2d4b7428ebc..1dae500d0a81 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -91,8 +91,6 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, 
struct pt_regs *regs)
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
unsigned long probe_addr = (unsigned long)p->addr;
-   extern char __start_rodata[];
-   extern char __end_rodata[];
 
if (probe_addr & 0x3)
return -EINVAL;
@@ -106,10 +104,6 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
if (search_exception_tables(probe_addr))
return -EINVAL;
 
-   if (probe_addr >= (unsigned long) __start_rodata &&
-   probe_addr <= (unsigned long) __end_rodata)
-   return -EINVAL;
-
/* decode instruction */
switch (arm_kprobe_decode_insn(p->addr, >ainsn)) {
case INSN_REJECTED: /* insn not supported */