Le 10/11/2022 à 19:43, Hari Bathini a écrit :
> Use bpf_jit_binary_pack_alloc in powerpc jit. The jit engine first
> writes the program to the rw buffer. When the jit is done, the program
> is copied to the final location with bpf_jit_binary_pack_finalize.
> With multiple jit_subprogs, bpf_jit_free is called on some subprograms
> that haven't got bpf_jit_binary_pack_finalize() yet. Implement custom
> bpf_jit_free() like in commit 1d5f82d9dd47 ("bpf, x86: fix freeing of
> not-finalized bpf_prog_pack") to call bpf_jit_binary_pack_finalize(),
> if necessary. While here, correct the misnomer powerpc64_jit_data to
> powerpc_jit_data as it is meant for both ppc32 and ppc64.
This patch looks heavy compared to x86 commit 1022a5498f6f.
I didn't look into details, is there really a need to carry that
rw_image over all functions you changed ?
As far as I can see, ok you need it for EMIT macro. But then some of the
function that use EMIT will now use rw_image instead of image, so why do
they need both image and rw_image ?
Maybe you'd have less churn if you leave image, and add a ro_image
wherever necessary but not everywhere.
>
> Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> ---
> arch/powerpc/net/bpf_jit.h | 18 +++--
> arch/powerpc/net/bpf_jit_comp.c | 123 +++++++++++++++++++++---------
> arch/powerpc/net/bpf_jit_comp32.c | 26 +++----
> arch/powerpc/net/bpf_jit_comp64.c | 32 ++++----
> 4 files changed, 128 insertions(+), 71 deletions(-)
>
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index f925755cd249..c4c1f7a21d89 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -181,22 +183,25 @@ bool bpf_jit_needs_zext(void)
>
> struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> {
> - u32 proglen;
> - u32 alloclen;
> - u8 *image = NULL;
> - u32 *code_base;
> - u32 *addrs;
> - struct powerpc64_jit_data *jit_data;
> - struct codegen_context cgctx;
> - int pass;
> - int flen;
> + struct bpf_binary_header *rw_header = NULL;
> + struct powerpc_jit_data *jit_data;
> struct bpf_binary_header *bpf_hdr;
> + struct codegen_context cgctx;
> struct bpf_prog *org_fp = fp;
> struct bpf_prog *tmp_fp;
> bool bpf_blinded = false;
> bool extra_pass = false;
> + u8 *rw_image = NULL;
> + u32 *rw_code_base;
> + u8 *image = NULL;
> u32 extable_len;
> + u32 *code_base;
> u32 fixup_len;
> + u32 alloclen;
> + u32 proglen;
> + u32 *addrs;
> + int pass;
> + int flen;
Why so many changes here, a lot of items seems to only have moved
without any modification. Why that churn ?
>
> if (!fp->jit_requested)
> return org_fp;
> @@ -227,6 +232,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> image = jit_data->image;
> bpf_hdr = jit_data->header;
> proglen = jit_data->proglen;
> + rw_header = jit_data->rw_header;
> + rw_image = (void *)rw_header + ((void *)image - (void *)bpf_hdr);
> extra_pass = true;
> goto skip_init_ctx;
> }
> @@ -244,7 +251,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
>
> /* Scouting faux-generate pass 0 */
> - if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0)) {
> + if (bpf_jit_build_body(fp, 0, 0, &cgctx, addrs, 0)) {
Some of the 0s in this call are pointers. You should use NULL instead.
This comment applies to several other lines you have changed.
> /* We hit something illegal or unsupported. */
> fp = org_fp;
> goto out_addrs;
> @@ -259,7 +266,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> */
> if (cgctx.seen & SEEN_TAILCALL || !is_offset_in_branch_range((long)cgctx.idx * 4)) {
> cgctx.idx = 0;
> - if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0)) {
> + if (bpf_jit_build_body(fp, 0, 0, &cgctx, addrs, 0)) {
0 ==> NULL
> fp = org_fp;
> goto out_addrs;
> }
> @@ -271,9 +278,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> * update ctgtx.idx as it pretends to output instructions, then we can
> * calculate total size from idx.
> */
> - bpf_jit_build_prologue(0, &cgctx);
> + bpf_jit_build_prologue(0, 0, &cgctx);
> addrs[fp->len] = cgctx.idx * 4;
> - bpf_jit_build_epilogue(0, &cgctx);
> + bpf_jit_build_epilogue(0, 0, &cgctx);
0 ==> NULL
>
> fixup_len = fp->aux->num_exentries * BPF_FIXUP_LEN * 4;
> extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry);
> @@ -337,17 +348,26 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
>
> #ifdef CONFIG_PPC64_ELF_ABI_V1
> /* Function descriptor nastiness: Address + TOC */
> - ((u64 *)image)[0] = (u64)code_base;
> - ((u64 *)image)[1] = local_paca->kernel_toc;
> + ((u64 *)rw_image)[0] = (u64)code_base;
> + ((u64 *)rw_image)[1] = local_paca->kernel_toc;
Would be better to use 'struct func_desc'
And the #ifdef is not necessary, IS_ENABLED() would be enough.
> #endif
>
> fp->bpf_func = (void *)image;
> fp->jited = 1;
> fp->jited_len = proglen + FUNCTION_DESCR_SIZE;
>
> - bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + bpf_hdr->size);
> if (!fp->is_func || extra_pass) {
> - bpf_jit_binary_lock_ro(bpf_hdr);
> + /*
> + * bpf_jit_binary_pack_finalize fails in two scenarios:
> + * 1) header is not pointing to proper module memory;
Can that really happen ?
> + * 2) the arch doesn't support bpf_arch_text_copy().
The above cannot happen, you added support bpf_arch_text_copy() in patch
1. So why this comment ?
> + *
> + * Both cases are serious bugs that justify WARN_ON.
> + */
Case 2 would mean a bug in the compiler, if you can't trust your
compiler for that you can't trust it for anything else. That's odd.
> + if (WARN_ON(bpf_jit_binary_pack_finalize(fp, bpf_hdr, rw_header))) {
> + fp = org_fp;
> + goto out_addrs;
> + }
> bpf_prog_fill_jited_linfo(fp, addrs);
> out_addrs:
> kfree(addrs);
