From 252c765bd764a246a8bd516fabf6d6123df4a24f Mon Sep 17 00:00:00 2001 From: Tong Tiangen Date: Wed, 27 Oct 2021 11:18:22 +0000 Subject: riscv, bpf: Add BPF exception tables MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When a tracing BPF program attempts to read memory without using the bpf_probe_read() helper, the verifier marks the load instruction with the BPF_PROBE_MEM flag. Since the riscv JIT does not currently recognize this flag it falls back to the interpreter. Add support for BPF_PROBE_MEM, by appending an exception table to the BPF program. If the load instruction causes a data abort, the fixup infrastructure finds the exception table and fixes up the fault, by clearing the destination register and jumping over the faulting instruction. A more generic solution would add a "handler" field to the table entry, like on x86 and s390. The same issue in ARM64 is fixed in 800834285361 ("bpf, arm64: Add BPF exception tables"). Signed-off-by: Tong Tiangen Signed-off-by: Daniel Borkmann Tested-by: Pu Lehui Tested-by: Björn Töpel Acked-by: Björn Töpel Link: https://lore.kernel.org/bpf/20211027111822.3801679-1-tongtiangen@huawei.com --- arch/riscv/net/bpf_jit_core.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) (limited to 'arch/riscv/net/bpf_jit_core.c') diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c index fed86f42dfbe..7ccc809f2c19 100644 --- a/arch/riscv/net/bpf_jit_core.c +++ b/arch/riscv/net/bpf_jit_core.c @@ -41,12 +41,12 @@ bool bpf_jit_needs_zext(void) struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) { + unsigned int prog_size = 0, extable_size = 0; bool tmp_blinded = false, extra_pass = false; struct bpf_prog *tmp, *orig_prog = prog; int pass = 0, prev_ninsns = 0, i; struct rv_jit_data *jit_data; struct rv_jit_context *ctx; - unsigned int image_size = 0; if (!prog->jit_requested) return orig_prog; @@ -73,7 +73,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) if (ctx->offset) { extra_pass = true; - image_size = sizeof(*ctx->insns) * ctx->ninsns; + prog_size = sizeof(*ctx->insns) * ctx->ninsns; goto skip_init_ctx; } @@ -102,10 +102,13 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) if (ctx->ninsns == prev_ninsns) { if (jit_data->header) break; + /* obtain the actual image size */ + extable_size = prog->aux->num_exentries * + sizeof(struct exception_table_entry); + prog_size = sizeof(*ctx->insns) * ctx->ninsns; - image_size = sizeof(*ctx->insns) * ctx->ninsns; jit_data->header = - bpf_jit_binary_alloc(image_size, + bpf_jit_binary_alloc(prog_size + extable_size, &jit_data->image, sizeof(u32), bpf_fill_ill_insns); @@ -130,9 +133,13 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) goto out_offset; } + if (extable_size) + prog->aux->extable = (void *)ctx->insns + prog_size; + skip_init_ctx: pass++; ctx->ninsns = 0; + ctx->nexentries = 0; bpf_jit_build_prologue(ctx); if (build_body(ctx, extra_pass, NULL)) { @@ -143,11 +150,11 @@ skip_init_ctx: bpf_jit_build_epilogue(ctx); if (bpf_jit_enable > 1) - bpf_jit_dump(prog->len, image_size, pass, ctx->insns); + bpf_jit_dump(prog->len, prog_size, pass, ctx->insns); prog->bpf_func = (void *)ctx->insns; prog->jited = 1; - prog->jited_len = image_size; + prog->jited_len = prog_size; bpf_flush_icache(jit_data->header, ctx->insns + ctx->ninsns); -- cgit v1.2.3