Le 25/08/2023 à 17:18, Hari Bathini a écrit :
> Implement bpf_arch_text_invalidate and use it to fill unused part of
> the bpf_prog_pack with trap instructions when a BPF program is freed.
>
> Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> ---
> arch/powerpc/net/bpf_jit_comp.c | 22 +++++++++++++++++++---
> 1 file changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index 170ebf8ac0f2..7cd4cf53d61c 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -30,7 +30,7 @@ static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
> * Patch 'len' bytes of instructions from opcode to addr, one instruction
> * at a time. Returns addr on success. ERR_PTR(-EINVAL), otherwise.
> */
> -static void *bpf_patch_instructions(void *addr, void *opcode, size_t len)
> +static void *bpf_patch_instructions(void *addr, void *opcode, size_t len, bool fill_insn)
It's a pitty that you have to modify in patch 2 a function you have
added in patch 1 of the same series. Can't you have it right from the
begining ?
> {
> while (len > 0) {
> ppc_inst_t insn = ppc_inst_read(opcode);
> @@ -41,7 +41,8 @@ static void *bpf_patch_instructions(void *addr, void *opcode, size_t len)
>
> len -= ilen;
> addr = addr + ilen;
> - opcode = opcode + ilen;
> + if (!fill_insn)
> + opcode = opcode + ilen;
> }
>
> return addr;
> @@ -307,7 +308,22 @@ void *bpf_arch_text_copy(void *dst, void *src, size_t len)
> return ERR_PTR(-EINVAL);
>
> mutex_lock(&text_mutex);
> - ret = bpf_patch_instructions(dst, src, len);
> + ret = bpf_patch_instructions(dst, src, len, false);
> + mutex_unlock(&text_mutex);
> +
> + return ret;
> +}
> +
> +int bpf_arch_text_invalidate(void *dst, size_t len)
> +{
> + u32 insn = BREAKPOINT_INSTRUCTION;
> + int ret;
> +
> + if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
> + return -EINVAL;
> +
> + mutex_lock(&text_mutex);
> + ret = IS_ERR(bpf_patch_instructions(dst, &insn, len, true));
Why IS_ERR ?
As far as I understand from the weak definition in kernel/bpf/core.c,
this function is supposed to return an error, not a bool.
> mutex_unlock(&text_mutex);
>
> return ret;
