[PATCH v2 2/4] powerpc/bpf: implement bpf_arch_text_copy

[Song Liu]

On Thu, Mar 9, 2023 at 10:02 AM Hari Bathini <hbathini at linux.ibm.com> wrote:
>
> bpf_arch_text_copy is used to dump JITed binary to RX page, allowing
> multiple BPF programs to share the same page. Use the newly introduced
> patch_instructions() to implement it. Around 5X improvement in speed
> of execution observed, using the new patch_instructions() function
> over patch_instruction(), while running the tests from test_bpf.ko.
>
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
>  arch/powerpc/net/bpf_jit_comp.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index e93aefcfb83f..0a70319116d1 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -13,9 +13,12 @@
>  #include <linux/netdevice.h>
>  #include <linux/filter.h>
>  #include <linux/if_vlan.h>
> -#include <asm/kprobes.h>
> +#include <linux/memory.h>
>  #include <linux/bpf.h>
>
> +#include <asm/kprobes.h>
> +#include <asm/code-patching.h>
> +
>  #include "bpf_jit.h"
>
>  static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
> @@ -272,3 +275,21 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code
>         ctx->exentry_idx++;
>         return 0;
>  }
> +
> +void *bpf_arch_text_copy(void *dst, void *src, size_t len)
> +{
> +       void *ret = ERR_PTR(-EINVAL);
> +       int err;
> +
> +       if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
> +               return ret;
> +
> +       ret = dst;
> +       mutex_lock(&text_mutex);
> +       err = patch_instructions(dst, src, false, len);
> +       if (err)
> +               ret = ERR_PTR(err);
> +       mutex_unlock(&text_mutex);
> +
> +       return ret;
> +}

It seems we don't really need "ret". How about something like:

+void *bpf_arch_text_copy(void *dst, void *src, size_t len)
+{
+       int err;
+
+       if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
+               return ERR_PTR(-EINVAL);
+
+       mutex_lock(&text_mutex);
+       err = patch_instructions(dst, src, false, len);
+       mutex_unlock(&text_mutex);
+
+       return err ? ERR_PTR(err) : dst;
+}

Song