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riscv, bpf: Emit fixed-length instructions for BPF_PSEUDO_FUNC 

For BPF_PSEUDO_FUNC instruction, verifier will refill imm with
correct addresses of bpf_calls and then run last pass of JIT.
Since the emit_imm of RV64 is variable-length, which will emit
appropriate length instructions accorroding to the imm, it may
broke ctx->offset, and lead to unpredictable problem, such as
inaccurate jump. So let's fix it with fixed-length instructions.

Fixes: 69c087ba62 ("bpf: Add bpf_for_each_map_elem() helper")
Suggested-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20221206091410.1584784-1-pulehui@huaweicloud.com
This commit is contained in:
Pu Lehui 2022-12-06 17:14:10 +08:00 committed by Daniel Borkmann
parent 08388efe59
commit b54b600361
1 changed files with 28 additions and 1 deletions
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29
arch/riscv/net/bpf_jit_comp64.c
View File

@ -136,6 +136,25 @@ static bool in_auipc_jalr_range(s64 val)
val < ((1L << 31) - (1L << 11));
}
/* Emit fixed-length instructions for address */
static int emit_addr(u8 rd, u64 addr, bool extra_pass, struct rv_jit_context *ctx)
{
u64 ip = (u64)(ctx->insns + ctx->ninsns);
s64 off = addr - ip;
s64 upper = (off + (1 << 11)) >> 12;
s64 lower = off & 0xfff;
if (extra_pass && !in_auipc_jalr_range(off)) {
pr_err("bpf-jit: target offset 0x%llx is out of range\n", off);
return -ERANGE;
}
emit(rv_auipc(rd, upper), ctx);
emit(rv_addi(rd, rd, lower), ctx);
return 0;
}
/* Emit variable-length instructions for 32-bit and 64-bit imm */
static void emit_imm(u8 rd, s64 val, struct rv_jit_context *ctx)
{
/* Note that the immediate from the add is sign-extended,
@ -1050,7 +1069,15 @@ out_be:
u64 imm64;
imm64 = (u64)insn1.imm << 32 | (u32)imm;
emit_imm(rd, imm64, ctx);
if (bpf_pseudo_func(insn)) {
/* fixed-length insns for extra jit pass */
ret = emit_addr(rd, imm64, extra_pass, ctx);
if (ret)
return ret;
} else {
emit_imm(rd, imm64, ctx);
}
return 1;
}