From 1ee7ecb1f08cbc400b8ea0391c107e4ff890e25f Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Sun, 22 Oct 2023 13:29:26 +0200
Subject: [PATCH] all: prefer using utimensat()

---
 CMakeLists.txt | 29 ++++++++++++++++++++++++++++-
 src/work.cpp   | 26 +++++++++++++++++++++++---
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index abaa2610..1c1e100a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -169,6 +169,28 @@ endif()
 
 include(CheckCCompilerFlag)
 include(CheckIncludeFile)
+include(CheckFunctionExists)
+include(CheckStructHasMember)
+include(CheckSymbolExists)
+
+if(NOT DEFINED HAVE_UNISTD_H)
+    check_include_file("unistd.h" HAVE_UNISTD_H)
+endif()
+if(NOT DEFINED HAVE_UTIMENSAT)
+    check_function_exists(utimensat HAVE_UTIMENSAT_FUNCTION__)
+    if(HAVE_UTIMENSAT_FUNCTION__)
+        check_symbol_exists(utimensat "sys/types.h;fcntl.h;sys/stat.h" HAVE_UTIMENSAT_SYMBOL__)
+        if(HAVE_UTIMENSAT_SYMBOL__)
+            CHECK_STRUCT_HAS_MEMBER("struct stat" st_mtim.tv_nsec "sys/types.h;fcntl.h;sys/stat.h" HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC)
+            if (NOT HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC)
+                CHECK_STRUCT_HAS_MEMBER("struct stat" st_mtimespec.tv_nsec "sys/types.h;fcntl.h;sys/stat.h" HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC)
+            endif()
+            if (HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC OR HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC)
+                set(HAVE_UTIMENSAT 1)
+            endif()
+        endif()
+    endif()
+endif()
 
 if(UPX_CONFIG_DISABLE_WSTRICT)
     # enable all basic warnings
@@ -382,7 +404,6 @@ set(t upx_vendor_zlib)
 upx_compile_target_debug_with_O2(${t})
 upx_sanitize_target(${t})
 target_compile_definitions(${t} PRIVATE HAVE_VSNPRINTF=1)
-check_include_file("unistd.h" HAVE_UNISTD_H)
 if(HAVE_UNISTD_H)
     target_compile_definitions(${t} PRIVATE HAVE_UNISTD_H=1)
 endif()
@@ -429,6 +450,12 @@ endif()
 if(NOT UPX_CONFIG_DISABLE_ZSTD)
     target_compile_definitions(${t} PRIVATE WITH_ZSTD=1)
 endif()
+if(HAVE_UTIMENSAT)
+    target_compile_definitions(${t} PRIVATE USE_UTIMENSAT=1)
+    if (HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC)
+        target_compile_definitions(${t} PRIVATE HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC=1)
+    endif()
+endif()
 #upx_compile_target_debug_with_O2(${t})
 upx_sanitize_target(${t})
 if(MSVC_FRONTEND)
diff --git a/src/work.cpp b/src/work.cpp
index b2db6695..a5cfda7f 100644
--- a/src/work.cpp
+++ b/src/work.cpp
@@ -30,13 +30,20 @@
 // of class PackerBase which then does the actual work.
 // And see p_com.cpp for a simple executable format.
 
+#include "headers.h"
+#if USE_UTIMENSAT
+#include <sys/types.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#endif
 #include "conf.h"
 #include "file.h"
 #include "packmast.h"
 #include "ui.h"
 #include "util/membuffer.h"
 
-#if (ACC_OS_DOS32) && defined(__DJGPP__)
+#if USE_UTIMENSAT && defined(AT_FDCWD)
+#elif (ACC_OS_DOS32) && defined(__DJGPP__)
 #define USE_FTIME 1
 #elif ((ACC_OS_WIN32 || ACC_OS_WIN64) && (ACC_CC_INTELC || ACC_CC_MSC))
 #define USE__FUTIME 1
@@ -95,16 +102,29 @@ static void copy_file_contents(const char *iname, const char *oname, OpenMode om
 
 static void copy_file_attributes(const struct stat *st, const char *oname, bool preserve_mode,
                                  bool preserve_ownership, bool preserve_timestamp) noexcept {
-#if USE_UTIME
     // copy time stamp
     if (preserve_timestamp) {
+#if USE_UTIMENSAT && defined(AT_FDCWD)
+        struct timespec times[2];
+        memset(&times[0], 0, sizeof(times));
+#if HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC
+        times[0] = st->st_atimespec;
+        times[1] = st->st_mtimespec;
+#else
+        times[0] = st->st_atim;
+        times[1] = st->st_mtim;
+#endif
+        int r = utimensat(AT_FDCWD, oname, &times[0], 0);
+        IGNORE_ERROR(r);
+#elif USE_UTIME
         struct utimbuf u;
+        memset(&u, 0, sizeof(u));
         u.actime = st->st_atime;
         u.modtime = st->st_mtime;
         int r = utime(oname, &u);
         IGNORE_ERROR(r);
-    }
 #endif
+    }
 #if HAVE_CHOWN
     // copy the group ownership
     if (preserve_ownership) {