Merge "NetBpfLoad: workaround for Xiaomi kernel uapi bug" into main

bpf/loader/NetBpfLoad.cpp

@@ -59,6 +59,7 @@
 #include <android-base/unique_fd.h>
 #include <android/api-level.h>
 
+#define BPF_SUPPORT_CMD_FIXUP
 #include "BpfSyscallWrappers.h"
 #include "bpf/BpfUtils.h"
 #include "bpf_map_def.h"
@@ -1871,7 +1872,11 @@ static int doLoad(char** argv, char * const envp[]) {
             // which causes bpfGetNextMapId to behave as bpfGetNextProgId,
             // and thus it should return 0 with errno == ENOENT.
             ALOGE("bpfGetNextMapId(final %d) returned %d errno %d", mapId, next, errno);
-            return 1;
+            if (next || errno != ENOENT) return 1;
+            if (isAtLeastT || isAtLeastKernelVersion(4, 20, 0)) return 1;
+            // implies Android S with 4.14 or 4.19 kernel
+            ALOGW("Enabling bpfCmdFixupIsNeeded.");
+            bpfCmdFixupIsNeeded = true;
         }
     } else {  // implies S/T with 4.9 kernel
         // nothing we can do.

bpf/syscall_wrappers/include/BpfSyscallWrappers.h

@@ -34,18 +34,28 @@ inline uint64_t ptr_to_u64(const void * const x) {
     return (uint64_t)(uintptr_t)x;
 }
 
+#ifdef BPF_SUPPORT_CMD_FIXUP
+static bool bpfCmdFixupIsNeeded = false;
+#else
+static constexpr bool bpfCmdFixupIsNeeded = false;
+#endif
+
+inline long bpfCmdFixup(enum bpf_cmd cmd) {
+    return cmd + (cmd >= BPF_PROG_TEST_RUN && bpfCmdFixupIsNeeded);
+}
+
 /* Note: bpf_attr is a union which might have a much larger size then the anonymous struct portion
  * of it that we are using.  The kernel's bpf() system call will perform a strict check to ensure
  * all unused portions are zero.  It will fail with E2BIG if we don't fully zero bpf_attr.
  */
 
 inline int bpf(enum bpf_cmd cmd, const bpf_attr& attr) {
-    return syscall(__NR_bpf, cmd, &attr, sizeof(attr));
+    return syscall(__NR_bpf, bpfCmdFixup(cmd), &attr, sizeof(attr));
 }
 
 // this version is meant for use with cmd's which mutate the argument
 inline int bpf(enum bpf_cmd cmd, bpf_attr *attr) {
-    return syscall(__NR_bpf, cmd, attr, sizeof(*attr));
+    return syscall(__NR_bpf, bpfCmdFixup(cmd), attr, sizeof(*attr));
 }
 
 inline int createMap(bpf_map_type map_type, uint32_t key_size, uint32_t value_size,