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From: Arnd Bergmann <arnd@kernel.org>
To: Russell King <linux@armlinux.org.uk>, Christoph Hellwig <hch@lst.de>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-mm@kvack.org, viro@zeniv.linux.org.uk,
	linus.walleij@linaro.org, arnd@arndb.de
Subject: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
Date: Fri, 30 Oct 2020 16:49:11 +0100	[thread overview]
Message-ID: <20201030154919.1246645-1-arnd@kernel.org> (raw)
In-Reply-To: <20201030154519.1245983-1-arnd@kernel.org>

From: Arnd Bergmann <arnd@arndb.de>

On machines such as ARMv5 that trap unaligned accesses, these
two functions can be slow when each access needs to be emulated,
or they might not work at all.

Change them so that each loop is only used when both the src
and dst pointers are naturally aligned.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 mm/maccess.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/mm/maccess.c b/mm/maccess.c
index 3bd70405f2d8..d3f1a1f0b1c1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -24,13 +24,21 @@ bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
 
 long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
 {
+	unsigned long align = 0;
+
+	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+		align = (unsigned long)dst | (unsigned long)src;
+
 	if (!copy_from_kernel_nofault_allowed(src, size))
 		return -ERANGE;
 
 	pagefault_disable();
-	copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
-	copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
-	copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
+	if (!(align & 7))
+		copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
+	if (!(align & 3))
+		copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
+	if (!(align & 1))
+		copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
 	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
 	pagefault_enable();
 	return 0;
@@ -50,10 +58,18 @@ EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
 
 long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
 {
+	unsigned long align = 0;
+
+	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+		align = (unsigned long)dst | (unsigned long)src;
+
 	pagefault_disable();
-	copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
-	copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
-	copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
+	if (!(align & 7))
+		copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
+	if (!(align & 3))
+		copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
+	if (!(align & 1))
+		copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
 	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
 	pagefault_enable();
 	return 0;
-- 
2.27.0


WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@kernel.org>
To: Russell King <linux@armlinux.org.uk>, Christoph Hellwig <hch@lst.de>
Cc: linux-arch@vger.kernel.org, arnd@arndb.de,
	linus.walleij@linaro.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, viro@zeniv.linux.org.uk,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
Date: Fri, 30 Oct 2020 16:49:11 +0100	[thread overview]
Message-ID: <20201030154919.1246645-1-arnd@kernel.org> (raw)
In-Reply-To: <20201030154519.1245983-1-arnd@kernel.org>

From: Arnd Bergmann <arnd@arndb.de>

On machines such as ARMv5 that trap unaligned accesses, these
two functions can be slow when each access needs to be emulated,
or they might not work at all.

Change them so that each loop is only used when both the src
and dst pointers are naturally aligned.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 mm/maccess.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/mm/maccess.c b/mm/maccess.c
index 3bd70405f2d8..d3f1a1f0b1c1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -24,13 +24,21 @@ bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
 
 long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
 {
+	unsigned long align = 0;
+
+	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+		align = (unsigned long)dst | (unsigned long)src;
+
 	if (!copy_from_kernel_nofault_allowed(src, size))
 		return -ERANGE;
 
 	pagefault_disable();
-	copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
-	copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
-	copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
+	if (!(align & 7))
+		copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
+	if (!(align & 3))
+		copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
+	if (!(align & 1))
+		copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
 	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
 	pagefault_enable();
 	return 0;
@@ -50,10 +58,18 @@ EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
 
 long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
 {
+	unsigned long align = 0;
+
+	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+		align = (unsigned long)dst | (unsigned long)src;
+
 	pagefault_disable();
-	copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
-	copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
-	copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
+	if (!(align & 7))
+		copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
+	if (!(align & 3))
+		copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
+	if (!(align & 1))
+		copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
 	copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
 	pagefault_enable();
 	return 0;
-- 
2.27.0


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  parent reply	other threads:[~2020-10-30 15:49 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-30 15:45 [PATCH v4 0/9] ARM: remove set_fs callers and implementation Arnd Bergmann
2020-10-30 15:45 ` Arnd Bergmann
2020-10-30 15:45 ` [PATCH 3/9] ARM: oabi-compat: add epoll_pwait handler Arnd Bergmann
2020-10-30 15:49 ` Arnd Bergmann [this message]
2020-10-30 15:49   ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
2020-10-30 15:49   ` [PATCH 2/9] ARM: traps: use get_kernel_nofault instead of set_fs() Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-11-06  9:02     ` Linus Walleij
2020-11-06  9:02       ` Linus Walleij
2020-11-06  9:02       ` Linus Walleij
2020-10-30 15:49   ` [PATCH 3/9] ARM: oabi-compat: add epoll_pwait handler Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-10-30 15:49   ` [PATCH 4/9] ARM: syscall: always store thread_info->syscall Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-10-30 16:53     ` Russell King - ARM Linux admin
2020-10-30 16:53       ` Russell King - ARM Linux admin
2020-10-30 21:28       ` Arnd Bergmann
2020-10-30 21:28         ` Arnd Bergmann
2020-10-30 21:28         ` Arnd Bergmann
2020-10-30 15:49   ` [PATCH 5/9] ARM: oabi-compat: rework epoll_wait/epoll_pwait emulation Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-10-30 15:49   ` [PATCH 6/9] ARM: oabi-compat: rework sys_semtimedop emulation Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-10-30 15:49   ` [PATCH 7/9] ARM: oabi-compat: rework fcntl64() emulation Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-10-30 15:49   ` [PATCH 8/9] ARM: uaccess: add __{get,put}_kernel_nofault Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-10-30 15:49   ` [PATCH 9/9] ARM: uaccess: remove set_fs() implementation Arnd Bergmann
2020-10-30 15:49     ` Arnd Bergmann
2020-11-06  8:57   ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Linus Walleij
2020-11-06  8:57     ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from, to}_kernel_nofault Linus Walleij
2020-11-06  8:57     ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Linus Walleij
2020-11-06  9:36 ` [PATCH v4 0/9] ARM: remove set_fs callers and implementation Linus Walleij
2020-11-06  9:36   ` Linus Walleij
2020-11-06  9:36   ` Linus Walleij
  -- strict thread matches above, loose matches on Subject: below --
2020-09-07 15:36 [PATCH " Arnd Bergmann
2020-09-07 15:36 ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
2020-09-07 15:36   ` Arnd Bergmann
2020-09-08  6:11   ` Christoph Hellwig
2020-09-08  6:11     ` Christoph Hellwig
2020-09-27  9:25   ` Linus Walleij
2020-09-27  9:25     ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from, to}_kernel_nofault Linus Walleij
2020-09-27  9:25     ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Linus Walleij

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