From e2c95a61656d29ceaac97b6a975c8a1f26e26f15 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 26 Nov 2018 14:05:38 +0100 Subject: [PATCH 1/2] bpf, ppc64: generalize fetching subprog into bpf_jit_get_func_addr Make fetching of the BPF call address from ppc64 JIT generic. ppc64 was using a slightly different variant rather than through the insns' imm field encoding as the target address would not fit into that space. Therefore, the target subprog number was encoded into the insns' offset and fetched through fp->aux->func[off]->bpf_func instead. Given there are other JITs with this issue and the mechanism of fetching the address is JIT-generic, move it into the core as a helper instead. On the JIT side, we get information on whether the retrieved address is a fixed one, that is, not changing through JIT passes, or a dynamic one. For the former, JITs can optimize their imm emission because this doesn't change jump offsets throughout JIT process. Signed-off-by: Daniel Borkmann Reviewed-by: Sandipan Das Tested-by: Sandipan Das Signed-off-by: Alexei Starovoitov --- arch/powerpc/net/bpf_jit_comp64.c | 57 ++++++++++++++++++++----------- include/linux/filter.h | 4 +++ kernel/bpf/core.c | 34 ++++++++++++++++++ 3 files changed, 76 insertions(+), 19 deletions(-) diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index 50b129785aee..17482f5de3e2 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -166,7 +166,33 @@ static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) PPC_BLR(); } -static void bpf_jit_emit_func_call(u32 *image, struct codegen_context *ctx, u64 func) +static void bpf_jit_emit_func_call_hlp(u32 *image, struct codegen_context *ctx, + u64 func) +{ +#ifdef PPC64_ELF_ABI_v1 + /* func points to the function descriptor */ + PPC_LI64(b2p[TMP_REG_2], func); + /* Load actual entry point from function descriptor */ + PPC_BPF_LL(b2p[TMP_REG_1], b2p[TMP_REG_2], 0); + /* ... and move it to LR */ + PPC_MTLR(b2p[TMP_REG_1]); + /* + * Load TOC from function descriptor at offset 8. + * We can clobber r2 since we get called through a + * function pointer (so caller will save/restore r2) + * and since we don't use a TOC ourself. + */ + PPC_BPF_LL(2, b2p[TMP_REG_2], 8); +#else + /* We can clobber r12 */ + PPC_FUNC_ADDR(12, func); + PPC_MTLR(12); +#endif + PPC_BLRL(); +} + +static void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, + u64 func) { unsigned int i, ctx_idx = ctx->idx; @@ -273,7 +299,7 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, { const struct bpf_insn *insn = fp->insnsi; int flen = fp->len; - int i; + int i, ret; /* Start of epilogue code - will only be valid 2nd pass onwards */ u32 exit_addr = addrs[flen]; @@ -284,8 +310,9 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 src_reg = b2p[insn[i].src_reg]; s16 off = insn[i].off; s32 imm = insn[i].imm; + bool func_addr_fixed; + u64 func_addr; u64 imm64; - u8 *func; u32 true_cond; u32 tmp_idx; @@ -711,23 +738,15 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, case BPF_JMP | BPF_CALL: ctx->seen |= SEEN_FUNC; - /* bpf function call */ - if (insn[i].src_reg == BPF_PSEUDO_CALL) - if (!extra_pass) - func = NULL; - else if (fp->aux->func && off < fp->aux->func_cnt) - /* use the subprog id from the off - * field to lookup the callee address - */ - func = (u8 *) fp->aux->func[off]->bpf_func; - else - return -EINVAL; - /* kernel helper call */ + ret = bpf_jit_get_func_addr(fp, &insn[i], extra_pass, + &func_addr, &func_addr_fixed); + if (ret < 0) + return ret; + + if (func_addr_fixed) + bpf_jit_emit_func_call_hlp(image, ctx, func_addr); else - func = (u8 *) __bpf_call_base + imm; - - bpf_jit_emit_func_call(image, ctx, (u64)func); - + bpf_jit_emit_func_call_rel(image, ctx, func_addr); /* move return value from r3 to BPF_REG_0 */ PPC_MR(b2p[BPF_REG_0], 3); break; diff --git a/include/linux/filter.h b/include/linux/filter.h index de629b706d1d..448dcc448f1f 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -866,6 +866,10 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr); void bpf_jit_free(struct bpf_prog *fp); +int bpf_jit_get_func_addr(const struct bpf_prog *prog, + const struct bpf_insn *insn, bool extra_pass, + u64 *func_addr, bool *func_addr_fixed); + struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *fp); void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other); diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 1a796e0799ec..b1a3545d0ec8 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -672,6 +672,40 @@ void __weak bpf_jit_free(struct bpf_prog *fp) bpf_prog_unlock_free(fp); } +int bpf_jit_get_func_addr(const struct bpf_prog *prog, + const struct bpf_insn *insn, bool extra_pass, + u64 *func_addr, bool *func_addr_fixed) +{ + s16 off = insn->off; + s32 imm = insn->imm; + u8 *addr; + + *func_addr_fixed = insn->src_reg != BPF_PSEUDO_CALL; + if (!*func_addr_fixed) { + /* Place-holder address till the last pass has collected + * all addresses for JITed subprograms in which case we + * can pick them up from prog->aux. + */ + if (!extra_pass) + addr = NULL; + else if (prog->aux->func && + off >= 0 && off < prog->aux->func_cnt) + addr = (u8 *)prog->aux->func[off]->bpf_func; + else + return -EINVAL; + } else { + /* Address of a BPF helper call. Since part of the core + * kernel, it's always at a fixed location. __bpf_call_base + * and the helper with imm relative to it are both in core + * kernel. + */ + addr = (u8 *)__bpf_call_base + imm; + } + + *func_addr = (unsigned long)addr; + return 0; +} + static int bpf_jit_blind_insn(const struct bpf_insn *from, const struct bpf_insn *aux, struct bpf_insn *to_buff) From 8c11ea5ce13da0252fc92f91e90b0cb0c8fe5619 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 26 Nov 2018 14:05:39 +0100 Subject: [PATCH 2/2] bpf, arm64: fix getting subprog addr from aux for calls The arm64 JIT has the same issue as ppc64 JIT in that the relative BPF to BPF call offset can be too far away from core kernel in that relative encoding into imm is not sufficient and could potentially be truncated, see also fd045f6cd98e ("arm64: add support for module PLTs") which adds spill-over space for module_alloc() and therefore bpf_jit_binary_alloc(). Therefore, use the recently added bpf_jit_get_func_addr() helper for properly fetching the address through prog->aux->func[off]->bpf_func instead. This also has the benefit to optimize normal helper calls since their address can use the optimized emission. Tested on Cavium ThunderX CN8890. Fixes: db496944fdaa ("bpf: arm64: add JIT support for multi-function programs") Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov --- arch/arm64/net/bpf_jit_comp.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index a6fdaea07c63..89198017e8e6 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -351,7 +351,8 @@ static void build_epilogue(struct jit_ctx *ctx) * >0 - successfully JITed a 16-byte eBPF instruction. * <0 - failed to JIT. */ -static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) +static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, + bool extra_pass) { const u8 code = insn->code; const u8 dst = bpf2a64[insn->dst_reg]; @@ -625,12 +626,19 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) case BPF_JMP | BPF_CALL: { const u8 r0 = bpf2a64[BPF_REG_0]; - const u64 func = (u64)__bpf_call_base + imm; + bool func_addr_fixed; + u64 func_addr; + int ret; - if (ctx->prog->is_func) - emit_addr_mov_i64(tmp, func, ctx); + ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass, + &func_addr, &func_addr_fixed); + if (ret < 0) + return ret; + if (func_addr_fixed) + /* We can use optimized emission here. */ + emit_a64_mov_i64(tmp, func_addr, ctx); else - emit_a64_mov_i64(tmp, func, ctx); + emit_addr_mov_i64(tmp, func_addr, ctx); emit(A64_BLR(tmp), ctx); emit(A64_MOV(1, r0, A64_R(0)), ctx); break; @@ -753,7 +761,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) return 0; } -static int build_body(struct jit_ctx *ctx) +static int build_body(struct jit_ctx *ctx, bool extra_pass) { const struct bpf_prog *prog = ctx->prog; int i; @@ -762,7 +770,7 @@ static int build_body(struct jit_ctx *ctx) const struct bpf_insn *insn = &prog->insnsi[i]; int ret; - ret = build_insn(insn, ctx); + ret = build_insn(insn, ctx, extra_pass); if (ret > 0) { i++; if (ctx->image == NULL) @@ -858,7 +866,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) /* 1. Initial fake pass to compute ctx->idx. */ /* Fake pass to fill in ctx->offset. */ - if (build_body(&ctx)) { + if (build_body(&ctx, extra_pass)) { prog = orig_prog; goto out_off; } @@ -888,7 +896,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) build_prologue(&ctx, was_classic); - if (build_body(&ctx)) { + if (build_body(&ctx, extra_pass)) { bpf_jit_binary_free(header); prog = orig_prog; goto out_off;