From f76cbc7901f7d500f5a4f74aedfd29970d1efd00 Mon Sep 17 00:00:00 2001
From: Michel Dänzer <mdaenzer@redhat.com>
Date: Mon, 6 Jan 2020 18:24:52 +0100
Subject: util: Add os_same_file_description helper

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3202>
---
 src/util/os_file.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

(limited to 'src/util/os_file.c')

diff --git a/src/util/os_file.c b/src/util/os_file.c
index c670e127c6b..b502ff4b0ef 100644
--- a/src/util/os_file.c
+++ b/src/util/os_file.c
@@ -34,7 +34,9 @@ os_file_create_unique(const char *filename, int filemode)
 #if defined(__linux__)
 
 #include <fcntl.h>
+#include <linux/kcmp.h>
 #include <sys/stat.h>
+#include <sys/syscall.h>
 #include <unistd.h>
 
 
@@ -130,8 +132,18 @@ os_read_file(const char *filename)
    return buf;
 }
 
+bool
+os_same_file_description(int fd1, int fd2)
+{
+   pid_t pid = getpid();
+
+   return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2) == 0;
+}
+
 #else
 
+#include "u_debug.h"
+
 char *
 os_read_file(const char *filename)
 {
@@ -139,4 +151,15 @@ os_read_file(const char *filename)
    return NULL;
 }
 
+bool
+os_same_file_description(int fd1, int fd2)
+{
+   if (fd1 == fd2)
+      return true;
+
+   debug_warn_once("Can't tell if different file descriptors reference the same"
+                   " file description, false negatives might cause trouble!\n");
+   return false;
+}
+
 #endif
-- 
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