From 93bbb2555b65e582be9daebb752e1b8e7380da20 Mon Sep 17 00:00:00 2001 From: Björn Töpel Date: Tue, 31 Mar 2020 12:10:46 +0200 Subject: riscv, bpf: Remove BPF JIT for nommu builds MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The BPF JIT fails to build for kernels configured to !MMU. Without an MMU, the BPF JIT does not make much sense, therefore this patch disables the JIT for nommu builds. This was reported by the kbuild test robot: All errors (new ones prefixed by >>): arch/riscv/net/bpf_jit_comp64.c: In function 'bpf_jit_alloc_exec': >> arch/riscv/net/bpf_jit_comp64.c:1094:47: error: 'BPF_JIT_REGION_START' undeclared (first use in this function) 1094 | return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START, | ^~~~~~~~~~~~~~~~~~~~ arch/riscv/net/bpf_jit_comp64.c:1094:47: note: each undeclared identifier is reported only once for each function it appears in >> arch/riscv/net/bpf_jit_comp64.c:1095:9: error: 'BPF_JIT_REGION_END' undeclared (first use in this function) 1095 | BPF_JIT_REGION_END, GFP_KERNEL, | ^~~~~~~~~~~~~~~~~~ arch/riscv/net/bpf_jit_comp64.c:1098:1: warning: control reaches end of non-void function [-Wreturn-type] 1098 | } | ^ Reported-by: kbuild test robot Signed-off-by: Björn Töpel Signed-off-by: Daniel Borkmann Acked-by: Luke Nelson Link: https://lore.kernel.org/bpf/20200331101046.23252-1-bjorn.topel@gmail.com --- arch/riscv/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/riscv') diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 8672e77a5b7a..bd35ac72fe24 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -55,7 +55,7 @@ config RISCV select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_MMIOWB select ARCH_HAS_DEBUG_VIRTUAL - select HAVE_EBPF_JIT + select HAVE_EBPF_JIT if MMU select EDAC_SUPPORT select ARCH_HAS_GIGANTIC_PAGE select ARCH_WANT_HUGE_PMD_SHARE if 64BIT -- cgit v1.2.3-58-ga151 From 489553dd13a88d8a882db10622ba8b9b58582ce4 Mon Sep 17 00:00:00 2001 From: Luke Nelson Date: Mon, 6 Apr 2020 22:16:04 +0000 Subject: riscv, bpf: Fix offset range checking for auipc+jalr on RV64 The existing code in emit_call on RV64 checks that the PC-relative offset to the function fits in 32 bits before calling emit_jump_and_link to emit an auipc+jalr pair. However, this check is incorrect because offsets in the range [2^31 - 2^11, 2^31 - 1] cannot be encoded using auipc+jalr on RV64 (see discussion [1]). The RISC-V spec has recently been updated to reflect this fact [2, 3]. This patch fixes the problem by moving the check on the offset into emit_jump_and_link and modifying it to the correct range of encodable offsets, which is [-2^31 - 2^11, 2^31 - 2^11). This also enforces the check on the offset to other uses of emit_jump_and_link (e.g., BPF_JA) as well. Currently, this bug is unlikely to be triggered, because the memory region from which JITed images are allocated is close enough to kernel text for the offsets to not become too large; and because the bounds on BPF program size are small enough. This patch prevents this problem from becoming an issue if either of these change. [1]: https://groups.google.com/a/groups.riscv.org/forum/#!topic/isa-dev/bwWFhBnnZFQ [2]: https://github.com/riscv/riscv-isa-manual/commit/b1e42e09ac55116dbf9de5e4fb326a5a90e4a993 [3]: https://github.com/riscv/riscv-isa-manual/commit/4c1b2066ebd2965a422e41eb262d0a208a7fea07 Signed-off-by: Luke Nelson Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20200406221604.18547-1-luke.r.nels@gmail.com --- arch/riscv/net/bpf_jit_comp64.c | 49 +++++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 17 deletions(-) (limited to 'arch/riscv') diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index cc1985d8750a..d208a9fd6c52 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -110,6 +110,16 @@ static bool is_32b_int(s64 val) return -(1L << 31) <= val && val < (1L << 31); } +static bool in_auipc_jalr_range(s64 val) +{ + /* + * auipc+jalr can reach any signed PC-relative offset in the range + * [-2^31 - 2^11, 2^31 - 2^11). + */ + return (-(1L << 31) - (1L << 11)) <= val && + val < ((1L << 31) - (1L << 11)); +} + static void emit_imm(u8 rd, s64 val, struct rv_jit_context *ctx) { /* Note that the immediate from the add is sign-extended, @@ -380,20 +390,24 @@ static void emit_sext_32_rd(u8 *rd, struct rv_jit_context *ctx) *rd = RV_REG_T2; } -static void emit_jump_and_link(u8 rd, s64 rvoff, bool force_jalr, - struct rv_jit_context *ctx) +static int emit_jump_and_link(u8 rd, s64 rvoff, bool force_jalr, + struct rv_jit_context *ctx) { s64 upper, lower; if (rvoff && is_21b_int(rvoff) && !force_jalr) { emit(rv_jal(rd, rvoff >> 1), ctx); - return; + return 0; + } else if (in_auipc_jalr_range(rvoff)) { + upper = (rvoff + (1 << 11)) >> 12; + lower = rvoff & 0xfff; + emit(rv_auipc(RV_REG_T1, upper), ctx); + emit(rv_jalr(rd, RV_REG_T1, lower), ctx); + return 0; } - upper = (rvoff + (1 << 11)) >> 12; - lower = rvoff & 0xfff; - emit(rv_auipc(RV_REG_T1, upper), ctx); - emit(rv_jalr(rd, RV_REG_T1, lower), ctx); + pr_err("bpf-jit: target offset 0x%llx is out of range\n", rvoff); + return -ERANGE; } static bool is_signed_bpf_cond(u8 cond) @@ -407,18 +421,16 @@ static int emit_call(bool fixed, u64 addr, struct rv_jit_context *ctx) s64 off = 0; u64 ip; u8 rd; + int ret; if (addr && ctx->insns) { ip = (u64)(long)(ctx->insns + ctx->ninsns); off = addr - ip; - if (!is_32b_int(off)) { - pr_err("bpf-jit: target call addr %pK is out of range\n", - (void *)addr); - return -ERANGE; - } } - emit_jump_and_link(RV_REG_RA, off, !fixed, ctx); + ret = emit_jump_and_link(RV_REG_RA, off, !fixed, ctx); + if (ret) + return ret; rd = bpf_to_rv_reg(BPF_REG_0, ctx); emit(rv_addi(rd, RV_REG_A0, 0), ctx); return 0; @@ -429,7 +441,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, { bool is64 = BPF_CLASS(insn->code) == BPF_ALU64 || BPF_CLASS(insn->code) == BPF_JMP; - int s, e, rvoff, i = insn - ctx->prog->insnsi; + int s, e, rvoff, ret, i = insn - ctx->prog->insnsi; struct bpf_prog_aux *aux = ctx->prog->aux; u8 rd = -1, rs = -1, code = insn->code; s16 off = insn->off; @@ -699,7 +711,9 @@ out_be: /* JUMP off */ case BPF_JMP | BPF_JA: rvoff = rv_offset(i, off, ctx); - emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx); + ret = emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx); + if (ret) + return ret; break; /* IF (dst COND src) JUMP off */ @@ -801,7 +815,6 @@ out_be: case BPF_JMP | BPF_CALL: { bool fixed; - int ret; u64 addr; mark_call(ctx); @@ -826,7 +839,9 @@ out_be: break; rvoff = epilogue_offset(ctx); - emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx); + ret = emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx); + if (ret) + return ret; break; /* dst = imm64 */ -- cgit v1.2.3-58-ga151