netdev - [PATCH bpf] riscv, bpf: Fix kfunc parameters incompatibility between bpf and riscv abi

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240324103306.2202954-1-pulehui@huaweicloud.com>
Date: Sun, 24 Mar 2024 10:33:06 +0000
From: Pu Lehui <pulehui@...weicloud.com>
To: bpf@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	netdev@...r.kernel.org
Cc: Björn Töpel <bjorn@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Luke Nelson <luke.r.nels@...il.com>,
	Pu Lehui <pulehui@...wei.com>,
	Pu Lehui <pulehui@...weicloud.com>
Subject: [PATCH bpf] riscv, bpf: Fix kfunc parameters incompatibility between bpf and riscv abi

From: Pu Lehui <pulehui@...wei.com>

We encountered a failing case when running selftest in no_alu32 mode:

The failure case is `kfunc_call/kfunc_call_test4` and its source code is
like bellow:
```
long bpf_kfunc_call_test4(signed char a, short b, int c, long d) __ksym;
int kfunc_call_test4(struct __sk_buff *skb)
{
	...
	tmp = bpf_kfunc_call_test4(-3, -30, -200, -1000);
	...
}
```

And its corresponding asm code is:
```
0: r1 = -3
1: r2 = -30
2: r3 = 0xffffff38 # opcode: 18 03 00 00 38 ff ff ff 00 00 00 00 00 00 00 00
4: r4 = -1000
5: call bpf_kfunc_call_test4
```

insn 2 is parsed to ld_imm64 insn to emit 0x00000000ffffff38 imm, and
converted to int type and then send to bpf_kfunc_call_test4. But since
it is zero-extended in the bpf calling convention, riscv jit will
directly treat it as an unsigned 32-bit int value, and then fails with
the message "actual 4294966063 != expected -1234".

The reason is the incompatibility between bpf and riscv abi, that is,
bpf will do zero-extension on uint, but riscv64 requires sign-extension
on int or uint. We can solve this problem by sign extending the 32-bit
parameters in kfunc.

The issue is related to [0], and thanks to Yonghong and Alexei.

Link: https://github.com/llvm/llvm-project/pull/84874 [0]
Fixes: d40c3847b485 ("riscv, bpf: Add kfunc support for RV64")
Signed-off-by: Pu Lehui <pulehui@...wei.com>
---
 arch/riscv/net/bpf_jit_comp64.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 869e4282a2c4..e3fc39370f7d 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1454,6 +1454,22 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 		if (ret < 0)
 			return ret;
 
+		if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
+			const struct btf_func_model *fm;
+			int idx;
+
+			fm = bpf_jit_find_kfunc_model(ctx->prog, insn);
+			if (!fm)
+				return -EINVAL;
+
+			for (idx = 0; idx < fm->nr_args; idx++) {
+				u8 reg = bpf_to_rv_reg(BPF_REG_1 + idx, ctx);
+
+				if (fm->arg_size[idx] == sizeof(int))
+					emit_sextw(reg, reg, ctx);
+			}
+		}
+
 		ret = emit_call(addr, fixed_addr, ctx);
 		if (ret)
 			return ret;
-- 
2.34.1