--- /dev/null
+From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
+Subject: [PATCH v2] io: Do not implement fstat with fstatat
+Date: Mon, 11 Sep 2023 10:25:48 -0300
+
+AT_EMPTY_PATH is a requirement to implement fstat over fstatat,
+however it does not prevent the kernel to read the path argument.
+It is not an issue, but on x86-64 with SMAP-capable CPUs the kernel is
+forced to perform expensive user memory access. After that regular
+lookup is performed which adds even more overhead.
+
+Instead, issue the fstat syscall directly on LFS fstat implementation
+(32 bit architectures will still continue to use statx, which is
+required to have 64 bit time_t support). it should be even a
+small performance gain on non x86_64, since there is no need
+to handle the path argument.
+
+Checked on x86_64-linux-gnu.
+---
+ sysdeps/unix/sysv/linux/fstat64.c | 37 +++++++++++++++++++++++--
+ sysdeps/unix/sysv/linux/fstatat64.c | 12 ++------
+ sysdeps/unix/sysv/linux/internal-stat.h | 31 +++++++++++++++++++++
+ 3 files changed, 68 insertions(+), 12 deletions(-)
+ create mode 100644 sysdeps/unix/sysv/linux/internal-stat.h
+
+diff --git a/sysdeps/unix/sysv/linux/fstat64.c b/sysdeps/unix/sysv/linux/fstat64.c
+index 124384e57f..a291f0825b 100644
+--- a/sysdeps/unix/sysv/linux/fstat64.c
++++ b/sysdeps/unix/sysv/linux/fstat64.c
+@@ -19,20 +19,53 @@
+ #define __fstat __redirect___fstat
+ #define fstat __redirect_fstat
+ #include <sys/stat.h>
++#undef __fstat
++#undef fstat
+ #include <fcntl.h>
+-#include <kernel_stat.h>
+-#include <stat_t64_cp.h>
++#include <internal-stat.h>
+ #include <errno.h>
+
+ int
+ __fstat64_time64 (int fd, struct __stat64_t64 *buf)
+ {
++#if !FSTATAT_USE_STATX
++# if XSTAT_IS_XSTAT64
++# ifdef __NR_fstat
++ /* 64-bit kABI, e.g. aarch64, ia64, powerpc64*, s390x, riscv64, and
++ x86_64. */
++ return INLINE_SYSCALL_CALL (fstat, fd, buf);
++# elif defined __NR_fstat64
++# if STAT64_IS_KERNEL_STAT64
++ /* 64-bit kABI outlier, e.g. alpha */
++ return INLINE_SYSCALL_CALL (fstat64, fd, buf);
++# else
++ /* 64-bit kABI outlier, e.g. sparc64. */
++ struct kernel_stat64 kst64;
++ int r = INLINE_SYSCALL_CALL (fstat64, fd, &kst64);
++ if (r == 0)
++ __cp_stat64_kstat64 (buf, &kst64);
++ return r;
++# endif /* STAT64_IS_KERNEL_STAT64 */
++# endif
++# else /* XSTAT_IS_XSTAT64 */
++ /* 64-bit kabi outlier, e.g. mips64 and mips64-n32. */
++ struct kernel_stat kst;
++ int r = INLINE_SYSCALL_CALL (fstat, fd, &kst);
++ if (r == 0)
++ __cp_kstat_stat64_t64 (&kst, buf);
++ return r;
++# endif
++#else /* !FSTATAT_USE_STATX */
++ /* All kABIs with non-LFS support and with old 32-bit time_t support
++ e.g. arm, csky, i386, hppa, m68k, microblaze, nios2, sh, powerpc32,
++ and sparc32. */
+ if (fd < 0)
+ {
+ __set_errno (EBADF);
+ return -1;
+ }
+ return __fstatat64_time64 (fd, "", buf, AT_EMPTY_PATH);
++#endif
+ }
+ #if __TIMESIZE != 64
+ hidden_def (__fstat64_time64)
+diff --git a/sysdeps/unix/sysv/linux/fstatat64.c b/sysdeps/unix/sysv/linux/fstatat64.c
+index 3509d3ca6d..127c6ff601 100644
+--- a/sysdeps/unix/sysv/linux/fstatat64.c
++++ b/sysdeps/unix/sysv/linux/fstatat64.c
+@@ -21,12 +21,10 @@
+ #include <sys/stat.h>
+ #include <fcntl.h>
+ #include <string.h>
+-#include <kernel_stat.h>
+ #include <sysdep.h>
+ #include <time.h>
+-#include <kstat_cp.h>
+-#include <stat_t64_cp.h>
+ #include <sys/sysmacros.h>
++#include <internal-stat.h>
+
+ #if __TIMESIZE == 64 \
+ && (__WORDSIZE == 32 \
+@@ -40,11 +38,7 @@ _Static_assert (sizeof (__blkcnt_t) == sizeof (__blkcnt64_t),
+ "__blkcnt_t and __blkcnt64_t must match");
+ #endif
+
+-#if (__WORDSIZE == 32 \
+- && (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE == 32)) \
+- || defined STAT_HAS_TIME32 \
+- || (!defined __NR_newfstatat && !defined __NR_fstatat64)
+-# define FSTATAT_USE_STATX 1
++#if FSTATAT_USE_STATX
+
+ static inline int
+ fstatat64_time64_statx (int fd, const char *file, struct __stat64_t64 *buf,
+@@ -79,8 +73,6 @@ fstatat64_time64_statx (int fd, const char *file, struct __stat64_t64 *buf,
+
+ return r;
+ }
+-#else
+-# define FSTATAT_USE_STATX 0
+ #endif
+
+ /* Only statx supports 64-bit timestamps for 32-bit architectures with
+diff --git a/sysdeps/unix/sysv/linux/internal-stat.h b/sysdeps/unix/sysv/linux/internal-stat.h
+new file mode 100644
+index 0000000000..e3b0569853
+--- /dev/null
++++ b/sysdeps/unix/sysv/linux/internal-stat.h
+@@ -0,0 +1,31 @@
++/* Internal stat definitions.
++ Copyright (C) 2023 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
++ modify it under the terms of the GNU Lesser General Public
++ License as published by the Free Software Foundation; either
++ version 2.1 of the License, or (at your option) any later version.
++
++ The GNU C Library is distributed in the hope that it will be useful,
++ but WITHOUT ANY WARRANTY; without even the implied warranty of
++ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
++ Lesser General Public License for more details.
++
++ You should have received a copy of the GNU Lesser General Public
++ License along with the GNU C Library; if not, see
++ <https://www.gnu.org/licenses/>. */
++
++#include <sysdep.h>
++#include <stat_t64_cp.h>
++#include <kernel_stat.h>
++#include <kstat_cp.h>
++
++#if (__WORDSIZE == 32 \
++ && (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE == 32)) \
++ || defined STAT_HAS_TIME32 \
++ || (!defined __NR_newfstatat && !defined __NR_fstatat64)
++# define FSTATAT_USE_STATX 1
++#else
++# define FSTATAT_USE_STATX 0
++#endif
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