Re: [PATCH v5 12/21] powerpc: Introduce a function for reporting instruction length

[Balamuruhan S <bala24@linux.ibm.com>]

On Mon, 2020-04-06 at 18:09 +1000, Jordan Niethe wrote:
> Currently all instructions have the same length, but in preparation for
> prefixed instructions introduce a function for returning instruction
> length.
> 
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
>  arch/powerpc/include/asm/inst.h | 5 +++++
>  arch/powerpc/kernel/kprobes.c   | 6 ++++--
>  arch/powerpc/kernel/uprobes.c   | 2 +-
>  3 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/inst.h
> b/arch/powerpc/include/asm/inst.h
> index 369b35ce964c..70b37a35a91a 100644
> --- a/arch/powerpc/include/asm/inst.h
> +++ b/arch/powerpc/include/asm/inst.h
> @@ -17,6 +17,11 @@ static inline u32 ppc_inst_val(struct ppc_inst x)
>  	return x.val;
>  }
>  
> +static inline bool ppc_inst_len(struct ppc_inst x)


return type shouldn't be a bool, `size_t` instead.

-- Bala

> +{
> +	return sizeof(struct ppc_inst);
> +}
> +
>  static inline int ppc_inst_opcode(struct ppc_inst x)
>  {
>  	return x.val >> 26;
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index ff53e5ef7e40..8d17cfdcdc54 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -474,14 +474,16 @@ NOKPROBE_SYMBOL(trampoline_probe_handler);
>   */
>  int kprobe_post_handler(struct pt_regs *regs)
>  {
> +	int len;
>  	struct kprobe *cur = kprobe_running();
>  	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
>  
>  	if (!cur || user_mode(regs))
>  		return 0;
>  
> +	len = ppc_inst_len(ppc_inst_read((struct ppc_inst *)cur->ainsn.insn));
>  	/* make sure we got here for instruction we have a kprobe on */
> -	if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
> +	if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
>  		return 0;
>  
>  	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
> @@ -490,7 +492,7 @@ int kprobe_post_handler(struct pt_regs *regs)
>  	}
>  
>  	/* Adjust nip to after the single-stepped instruction */
> -	regs->nip = (unsigned long)cur->addr + 4;
> +	regs->nip = (unsigned long)cur->addr + len;
>  	regs->msr |= kcb->kprobe_saved_msr;
>  
>  	/*Restore back the original saved kprobes variables and continue. */
> diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c
> index 31c870287f2b..8e63afa012ba 100644
> --- a/arch/powerpc/kernel/uprobes.c
> +++ b/arch/powerpc/kernel/uprobes.c
> @@ -112,7 +112,7 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe,
> struct pt_regs *regs)
>  	 * support doesn't exist and have to fix-up the next instruction
>  	 * to be executed.
>  	 */
> -	regs->nip = utask->vaddr + MAX_UINSN_BYTES;
> +	regs->nip = utask->vaddr + ppc_inst_len(auprobe->insn);
>  
>  	user_disable_single_step(current);
>  	return 0;