On Sun, Nov 03, 2024 at 11:35:12AM -0800, Kumar Kartikeya Dwivedi wrote:
> arch/x86/net/bpf_jit_comp.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index 06b080b61aa5..7e3bd589efc3 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -1954,8 +1954,8 @@ st: if (is_imm8(insn->off))
> case BPF_LDX | BPF_PROBE_MEMSX | BPF_W:
> insn_off = insn->off;
>
> - if (BPF_MODE(insn->code) == BPF_PROBE_MEM ||
> - BPF_MODE(insn->code) == BPF_PROBE_MEMSX) {
> + if ((BPF_MODE(insn->code) == BPF_PROBE_MEM ||
> + BPF_MODE(insn->code) == BPF_PROBE_MEMSX) && !cpu_feature_enabled(X86_FEATURE_SMAP)) {
> /* Conservatively check that src_reg + insn->off is a kernel address:
> * src_reg + insn->off > TASK_SIZE_MAX + PAGE_SIZE
> * and
Well, I can see why you'd want to get rid of that, that's quite
dreadful code you generate there.
Can't you do something like:
lea off(%src), %r10
mov %r10, %r11
inc %r10
sar $63, %r11
and %r11, %r10
dec %r10
mov (%r10), %rax
I realize that's not exactly pretty either, but no jumps. Not sure
this'll help much if anything with the TDX thing though.
