linux: Consolidate fxstatat{64}

The LFS support is implemented on fxstat64.c, instead of fxstat.c for
64-bit architectures.  The fxstatat.c implements the non-LFS and it is
a no-op for !XSTAT_IS_XSTAT64.

The generic non-LFS implementation handles two cases:

  1. New kABIs which uses generic pre 64-bit time Linux ABI (csky and
     nios): it issues __NR_fstatat64 plus handle the overflow on st_ino,
     st_size, or st_blocks.  It only handles _STAT_VER_KERNEL.

  2. Old kABIs with old non-LFS support (arm, i386, hppa, m68k, mips32,
     microblaze, s390, sh, powerpc, and sparc32).  it issues
     __NR_fstatat64 and convert to non-LFS stat struct based on the
     version.

Also non-LFS mips64 is an outlier and it has its own implementation
since _STAT_VER_LINUX requires a different conversion function (it
uses the kernel_stat as the sysissues argument since its exported ABI
is different than the kernel one for both non-LFS and LFS
implementation).

The generic LFS implementation handles multiple cases:

  1. XSTAT_IS_XSTAT64 being 1:

    1.1. 64-bit kABI (aarch64, ia64, powerpc64*, s390x, riscv64, and
         x86_64): it issues __NR_newfstatat for _STAT_VER_KERNEL or
         _STAT_VER_LINUX.

    1.2. 64-bit kABI outlier (sparc64): it issuess fstatat64 with a
         temporary stat64 and convert to output stat64 based on the
         input version (and using a sparc64 specific __xstat32_conv).

    1.3. New 32-bit kABIs with only 64-bit time_t support (arc and
	 riscv32): it issues __NR_statx and covert to struct stat64.

  2. Old ABIs with XSTAT_IS_XSTAT64 being 0 (arm, csky, i386, hppa, m68k,
     microblaze, mips32, nios2, sh, powerpc32, and sparc32): it issues
     __NR_fstat64.

Also, two special cases requires specific implementations:

  1. alpha: it uses the __NR_fstatat64 syscall instead.

  2. mips64: as for non-LFS implementation its ABIs differ from
     glibc exported one, which requires an specific conversion
     function to handle the kernel_stat.

Checked with a build for all affected ABIs. I also checked on x86_64,
i686, powerpc, powerpc64le, sparcv9, sparc64, s390, and s390x.

Reviewed-by: Lukasz Majewski <lukma@denx.de>

1 files changed, 21 insertions, 32 deletions

diff --git a/sysdeps/unix/sysv/linux/fxstatat.c b/sysdeps/unix/sysv/linux/fxstatat.c
index 937fec45c2..0291a2c598 100644
--- a/sysdeps/unix/sysv/linux/fxstatat.c
+++ b/sysdeps/unix/sysv/linux/fxstatat.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2005-2020 Free Software Foundation, Inc.
+/* fxstatat used on fstatat, Linux implementation.
+   Copyright (C) 2005-2020 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -15,48 +16,36 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-/* Ho hum, if fxstatat == fxstatat64 we must get rid of the prototype or gcc
-   will complain since they don't strictly match.  */
-#define __fxstatat64 __fxstatat64_disable
-
-#include <errno.h>
-#include <fcntl.h>
-#include <stddef.h>
-#include <stdio.h>
-#include <string.h>
 #include <sys/stat.h>
+#include <fcntl.h>
 #include <kernel_stat.h>
-
 #include <sysdep.h>
-#include <sys/syscall.h>
 
-#include <xstatconv.h>
+#if !XSTAT_IS_XSTAT64
+# include <xstatconv.h>
+# include <xstatover.h>
 
-/* Get information about the file NAME in BUF.  */
+/* Get information about the file FD in BUF.  */
 int
 __fxstatat (int vers, int fd, const char *file, struct stat *st, int flag)
 {
-  int result;
 #if STAT_IS_KERNEL_STAT
-# define kst (*st)
-#else
-  struct kernel_stat kst;
-#endif
-
-  result = INTERNAL_SYSCALL_CALL (newfstatat, fd, file, &kst, flag);
-  if (!__glibc_likely (INTERNAL_SYSCALL_ERROR_P (result)))
+  /* New kABIs which uses generic pre 64-bit time Linux ABI, e.g.
+     csky, nios2  */
+  if (vers == _STAT_VER_KERNEL)
     {
-#if STAT_IS_KERNEL_STAT
-      return 0;
+      int r = INLINE_SYSCALL_CALL (fstatat64, fd, file, st, flag);
+      return r ?: stat_overflow (st);
+    }
+  return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
 #else
-      return __xstat_conv (vers, &kst, st);
+  /* Old kABIs with old non-LFS support, e.g. arm, i386, hppa, m68k, mips32,
+     microblaze, s390, sh, powerpc32, and sparc32.  */
+  struct stat64 st64;
+  int r = INLINE_SYSCALL_CALL (fstatat64, fd, file, &st64, flag);
+  return r ?: __xstat32_conv (vers, &st64, st);
 #endif
-    }
-  return INLINE_SYSCALL_ERROR_RETURN_VALUE (INTERNAL_SYSCALL_ERRNO (result));
 }
 libc_hidden_def (__fxstatat)
-#if XSTAT_IS_XSTAT64
-# undef __fxstatat64
-strong_alias (__fxstatat, __fxstatat64);
-libc_hidden_def (__fxstatat64)
-#endif
+
+#endif /* XSTAT_IS_XSTAT64  */