Messages in this thread | | | From | Alexei Starovoitov <> | Date | Wed, 22 Nov 2023 16:51:23 -0800 | Subject | Re: [PATCH 2/2] x86/cfi,bpf: Fix BPF JIT call |
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On Wed, Nov 22, 2023 at 4:41 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > +/* > + * Emit the various CFI preambles, see the large comment about FineIBT > + * in arch/x86/kernel/alternative.c
.. and in cfi.h .. which will have a copy-paste from your other email?
> prog->bpf_func = (void *)image + ctx.prog_offset; > prog->jited = 1; > prog->jited_len = proglen - ctx.prog_offset; // XXX?
Just drop XXX.
> --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -1431,6 +1431,9 @@ struct bpf_prog_aux { > struct bpf_kfunc_desc_tab *kfunc_tab; > struct bpf_kfunc_btf_tab *kfunc_btf_tab; > u32 size_poke_tab; > +#ifdef CONFIG_FINEIBT > + struct bpf_ksym ksym_prefix; > +#endif > struct bpf_ksym ksym; > const struct bpf_prog_ops *ops; > struct bpf_map **used_maps; > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -683,6 +683,23 @@ void bpf_prog_kallsyms_add(struct bpf_pr > fp->aux->ksym.prog = true; > > bpf_ksym_add(&fp->aux->ksym); > + > +#ifdef CONFIG_FINEIBT > + /* > + * When FineIBT, code in the __cfi_foo() symbols can get executed > + * and hence unwinder needs help. > + */
I like the idea!
> + if (cfi_mode != CFI_FINEIBT) > + return;
The cfi_mode var needs to be global along with enum ? Or some new helper function from arch/x86 ?
> + > + snprintf(fp->aux->ksym_prefix.name, KSYM_NAME_LEN, > + "__cfi_%s", fp->aux->ksym.name); > + > + prog->aux->ksym_prefix.start = (unsigned long) prog->bpf_func - 16; > + prog->aux->ksym_prefix.end = (unsigned long) prog->bpf_func; > + > + bpf_ksym_add(&fp->aux->ksym_prefix); > +#endif > } > > void bpf_prog_kallsyms_del(struct bpf_prog *fp)
and handle deletion of ksym_prefix here.
I think it's shaping up nicely. Pls resend both patches as a set and cc bpf @ vger. BPF CI will pick it up and test on arm64, x86-64, s390 with gcc and clang. We don't do CONFIG_*IBT testing automatically, but I can manually try that after the holidays.
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