[PATCH] powerpc: Add ppc_inst_as_u64()

[Jordan Niethe]

On Mon, May 25, 2020 at 3:49 PM Michael Ellerman <mpe at ellerman.id.au> wrote:
>
> The code patching code wants to get the value of a struct ppc_inst as
Might need to change the wording here as it also gets used in
arch_prepare_optimized_kprobe()
> a u64 when the instruction is prefixed, so we can pass the u64 down to
> __put_user_asm() and write it with a single store.
>
> This is a bit awkward because the value differs based on the CPU
> endianness, so add a helper to do the conversion.
>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> ---
>  arch/powerpc/include/asm/inst.h  | 9 +++++++++
>  arch/powerpc/kernel/optprobes.c  | 3 +--
>  arch/powerpc/lib/code-patching.c | 8 +-------
>  3 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
> index d82e0c99cfa1..d61e07fb2937 100644
> --- a/arch/powerpc/include/asm/inst.h
> +++ b/arch/powerpc/include/asm/inst.h
> @@ -100,6 +100,15 @@ static inline int ppc_inst_len(struct ppc_inst x)
>         return ppc_inst_prefixed(x) ? 8 : 4;
>  }
>
> +static inline u64 ppc_inst_as_u64(struct ppc_inst x)
> +{
> +#ifdef CONFIG_CPU_LITTLE_ENDIAN
> +       return (u64)ppc_inst_suffix(x) << 32 | ppc_inst_val(x);
> +#else
> +       return (u64)ppc_inst_val(x) << 32 | ppc_inst_suffix(x);
> +#endif
> +}
> +
>  int probe_user_read_inst(struct ppc_inst *inst,
>                          struct ppc_inst __user *nip);
>
> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> index 3ac105e7faae..69bfe96884e2 100644
> --- a/arch/powerpc/kernel/optprobes.c
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -283,8 +283,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>          * 3. load instruction to be emulated into relevant register, and
>          */
>         temp = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
> -       patch_imm64_load_insns(ppc_inst_val(temp) | ((u64)ppc_inst_suffix(temp) << 32),
> -                              4, buff + TMPL_INSN_IDX);
> +       patch_imm64_load_insns(ppc_inst_as_u64(temp), 4, buff + TMPL_INSN_IDX);
>
>         /*
>          * 4. branch back from trampoline
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index 64cf621e5b00..5ecf0d635a8d 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -27,13 +27,7 @@ static int __patch_instruction(struct ppc_inst *exec_addr, struct ppc_inst instr
>         if (!ppc_inst_prefixed(instr)) {
>                 __put_user_asm(ppc_inst_val(instr), patch_addr, err, "stw");
>         } else {
> -#ifdef CONFIG_CPU_LITTLE_ENDIAN
> -               __put_user_asm((u64)ppc_inst_suffix(instr) << 32 |
> -                              ppc_inst_val(instr), patch_addr, err, "std");
> -#else
> -               __put_user_asm((u64)ppc_inst_val(instr) << 32 |
> -                              ppc_inst_suffix(instr), patch_addr, err, "std");
> -#endif
> +               __put_user_asm(ppc_inst_as_u64(instr), patch_addr, err, "std");
>         }
>
>         if (err)
> --
> 2.25.1
>
I booted a BE and LE kernel - test_prefixed_patching() worked on both.
Also on BE and LE kernels I put optprobes on prefixed and non prefixed
instructions.
The correct value was passed via r4 to emulate_step().

Tested-by: Jordan Niethe <jniethe5 at gmail.com>