[libc-commits] [libc] [libc] Change fcntl cmd when only fcntl64 is available (PR #99675)

[Mikhail R. Gadelha via libc-commits]

https://github.com/mikhailramalho created https://github.com/llvm/llvm-project/pull/99675

In some systems like rv32, only fcntl64 is available and it employs a different structure for file locking and the correspoding F_GETLK64, F_SETLK64, and F_SETLKW64 commands.

So if we use fcntl64, the F_GETLK, F_SETLK, and F_SETLKW commands need to be changed to their 64 versions. This patch adds new cases to the swich(cmd) in our implementation of fcntl to do that.

The default case was moved to outside the switch, so we don't need to change anything, the F_GETLK, F_SETLK, and F_SETLKW commands will just go through the old implementation.

>From 95e01ffdf02a5697f6f5792fc7a56641a29001ba Mon Sep 17 00:00:00 2001
From: "Mikhail R. Gadelha" <mikhail at igalia.com>
Date: Fri, 19 Jul 2024 14:53:16 -0300
Subject: [PATCH] [libc] Change fcntl cmd when only fcntl64 is available

In some systems like rv32, only fcntl64 is available and it employs a
different structure for file locking and the correspoding F_GETLK64,
F_SETLK64, and F_SETLKW64 commands.

So if we use fcntl64, the F_GETLK, F_SETLK, and F_SETLKW commands need
to be changed to their 64 versions. This patch adds new cases to the
swich(cmd) in our implementation of fcntl to do that.

The default case was moved to outside the switch, so we don't need to
change anything, the F_GETLK, F_SETLK, and F_SETLKW commands will just
go through the old implementation.
---
 libc/src/__support/OSUtil/linux/fcntl.cpp | 36 ++++++++++++++++++-----
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/libc/src/__support/OSUtil/linux/fcntl.cpp b/libc/src/__support/OSUtil/linux/fcntl.cpp
index e11013121b04b..44f10b6c59766 100644
--- a/libc/src/__support/OSUtil/linux/fcntl.cpp
+++ b/libc/src/__support/OSUtil/linux/fcntl.cpp
@@ -86,17 +86,37 @@ int fcntl(int fd, int cmd, void *arg) {
     libc_errno = -ret;
     return -1;
   }
+  case F_GETLK: {
+#if defined(SYS_fcntl64)
+    if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
+      return fcntl(fd, F_GETLK64, arg);
+#endif
+    break;
+  }
+  case F_SETLK: {
+#if defined(SYS_fcntl64)
+    if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
+      return fcntl(fd, F_SETLK64, arg);
+#endif
+    break;
+  }
+  case F_SETLKW: {
+#if defined(SYS_fcntl64)
+    if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
+      return fcntl(fd, F_SETLKW64, arg);
+#endif
+    break;
+  }
   // The general case
-  default: {
-    int retVal = LIBC_NAMESPACE::syscall_impl<int>(
-        FCNTL_SYSCALL_ID, fd, cmd, reinterpret_cast<void *>(arg));
-    if (retVal >= 0) {
-      return retVal;
-    }
-    libc_errno = -retVal;
-    return -1;
+  default:;
   }
+  int retVal = LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd, cmd,
+                                                 reinterpret_cast<void *>(arg));
+  if (retVal >= 0) {
+    return retVal;
   }
+  libc_errno = -retVal;
+  return -1;
 }
 
 } // namespace internal