netdev - [PATCH bpf-next 1/2] libbpf: Fix accessing first syscall argument on RV64

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Message-Id: <20240829133453.882259-2-pulehui@huaweicloud.com>
Date: Thu, 29 Aug 2024 13:34:52 +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>,
	Ilya Leoshkevich <iii@...ux.ibm.com>,
	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 <yonghong.song@...ux.dev>,
	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>,
	Puranjay Mohan <puranjay@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Pu Lehui <pulehui@...wei.com>
Subject: [PATCH bpf-next 1/2] libbpf: Fix accessing first syscall argument on RV64

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

On RV64, as Ilya mentioned before [0], the first syscall parameter should be
accessed through orig_a0 (see arch/riscv64/include/asm/syscall.h),
otherwise it will cause selftests like bpf_syscall_macro, vmlinux,
test_lsm, etc. to fail on RV64. Let's fix it by using the struct pt_regs
style to provide access to it only through PT_REGS_PARM1_CORE_SYSCALL().

Link: https://lore.kernel.org/bpf/20220209021745.2215452-1-iii@linux.ibm.com [0]
Signed-off-by: Pu Lehui <pulehui@...wei.com>
---
 tools/lib/bpf/bpf_tracing.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 9314fa95f04e..388f30cf7914 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -351,6 +351,10 @@ struct pt_regs___arm64 {
  * https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#risc-v-calling-conventions
  */
 
+struct pt_regs___riscv {
+	unsigned long orig_a0;
+};
+
 /* riscv provides struct user_regs_struct instead of struct pt_regs to userspace */
 #define __PT_REGS_CAST(x) ((const struct user_regs_struct *)(x))
 #define __PT_PARM1_REG a0
@@ -362,12 +366,15 @@ struct pt_regs___arm64 {
 #define __PT_PARM7_REG a6
 #define __PT_PARM8_REG a7
 
-#define __PT_PARM1_SYSCALL_REG __PT_PARM1_REG
+#define __PT_PARM1_SYSCALL_REG orig_a0
 #define __PT_PARM2_SYSCALL_REG __PT_PARM2_REG
 #define __PT_PARM3_SYSCALL_REG __PT_PARM3_REG
 #define __PT_PARM4_SYSCALL_REG __PT_PARM4_REG
 #define __PT_PARM5_SYSCALL_REG __PT_PARM5_REG
 #define __PT_PARM6_SYSCALL_REG __PT_PARM6_REG
+#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1_CORE_SYSCALL(x)
+#define PT_REGS_PARM1_CORE_SYSCALL(x) \
+	BPF_CORE_READ((const struct pt_regs___riscv *)(x), __PT_PARM1_SYSCALL_REG)
 
 #define __PT_RET_REG ra
 #define __PT_FP_REG s0
-- 
2.34.1