loongfire: port loxilb to loongarch

[vincentmli]

attempting to port loxilb to loongfire, but loxilb libbpf is on 0.8 which does not have loongarch support

[vincentmli]

copied the loongarch from libbpf 1.2.3 and renamed loongarch to loongarch64 to libbpf 0.8 seems working ok

[root@fedora libbpf]# diff -u src/bpf_tracing.h src/bpf_tracing.h.loongarch 
--- src/bpf_tracing.h	2025-01-31 13:32:38.733091585 -0800
+++ src/bpf_tracing.h.loongarch	2025-01-31 13:32:05.732071368 -0800
@@ -30,6 +30,9 @@
 #elif defined(__TARGET_ARCH_arc)
 	#define bpf_target_arc
 	#define bpf_target_defined
+#elif defined(__TARGET_ARCH_loongarch64)
+        #define bpf_target_loongarch64
+        #define bpf_target_defined
 #else
 
 /* Fall back to what the compiler says */
@@ -60,6 +63,9 @@
 #elif defined(__arc__)
 	#define bpf_target_arc
 	#define bpf_target_defined
+#elif defined(__loongarch64__)
+        #define bpf_target_loongarch64
+        #define bpf_target_defined
 #endif /* no compiler target */
 
 #endif
@@ -256,6 +262,39 @@
 /* arc does not select ARCH_HAS_SYSCALL_WRAPPER. */
 #define PT_REGS_SYSCALL_REGS(ctx) ctx
 
+#elif defined(bpf_target_loongarch64)
+
+/*
+ * https://docs.kernel.org/loongarch/introduction.html
+ * https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
+ */
+
+/* loongarch provides struct user_pt_regs instead of struct pt_regs to userspace */
+#define __PT_REGS_CAST(x) ((const struct user_pt_regs *)(x))
+#define __PT_PARM1_REG regs[4]
+#define __PT_PARM2_REG regs[5]
+#define __PT_PARM3_REG regs[6]
+#define __PT_PARM4_REG regs[7]
+#define __PT_PARM5_REG regs[8]
+#define __PT_PARM6_REG regs[9]
+#define __PT_PARM7_REG regs[10]
+#define __PT_PARM8_REG regs[11]
+
+/* loongarch does not select ARCH_HAS_SYSCALL_WRAPPER. */
+#define PT_REGS_SYSCALL_REGS(ctx) ctx
+#define __PT_PARM1_SYSCALL_REG __PT_PARM1_REG
+#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_RET_REG regs[1]
+#define __PT_FP_REG regs[22]
+#define __PT_RC_REG regs[4]
+#define __PT_SP_REG regs[3]
+#define __PT_IP_REG csr_era
+
 #endif
 
 #if defined(bpf_target_defined)