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authorRussell King <rmk@dyn-67.arm.linux.org.uk>2009-06-14 10:59:32 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2009-06-14 10:59:32 +0100
commit98797a241e28b787b84d308b867ec4c5fe7bbdf8 (patch)
treeedd39824d91bd8cf33d8903e10ed337611483360 /arch
parentca8cbc8391cbd4d6e4304fc6b62682ed93d2b165 (diff)
parentc626e3f5ca1d95ad2204d3128c26e7678714eb55 (diff)
Merge branch 'copy_user' of git://git.marvell.com/orion into devel
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/Kconfig16
-rw-r--r--arch/arm/include/asm/uaccess.h2
-rw-r--r--arch/arm/lib/Makefile3
-rw-r--r--arch/arm/lib/clear_user.S3
-rw-r--r--arch/arm/lib/copy_to_user.S3
-rw-r--r--arch/arm/lib/uaccess_with_memcpy.c228
6 files changed, 253 insertions, 2 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c857111ab964..3473f8b8ede6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1091,6 +1091,22 @@ config ALIGNMENT_TRAP
correct operation of some network protocols. With an IP-only
configuration it is safe to say N, otherwise say Y.
+config UACCESS_WITH_MEMCPY
+ bool "Use kernel mem{cpy,set}() for {copy_to,clear}_user() (EXPERIMENTAL)"
+ depends on MMU && EXPERIMENTAL
+ default y if CPU_FEROCEON
+ help
+ Implement faster copy_to_user and clear_user methods for CPU
+ cores where a 8-word STM instruction give significantly higher
+ memory write throughput than a sequence of individual 32bit stores.
+
+ A possible side effect is a slight increase in scheduling latency
+ between threads sharing the same address space if they invoke
+ such copy operations with large buffers.
+
+ However, if the CPU data cache is using a write-allocate mode,
+ this option is unlikely to provide any performance gain.
+
endmenu
menu "Boot options"
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 7897464e0c24..0da9bc9b3b1d 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -386,7 +386,9 @@ do { \
#ifdef CONFIG_MMU
extern unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n);
extern unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n);
+extern unsigned long __must_check __copy_to_user_std(void __user *to, const void *from, unsigned long n);
extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
+extern unsigned long __must_check __clear_user_std(void __user *addr, unsigned long n);
#else
#define __copy_from_user(to,from,n) (memcpy(to, (void __force *)from, n), 0)
#define __copy_to_user(to,from,n) (memcpy((void __force *)to, from, n), 0)
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 866f84a586ff..030ba7219f48 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -29,6 +29,9 @@ else
endif
endif
+# using lib_ here won't override already available weak symbols
+obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o
+
lib-$(CONFIG_MMU) += $(mmu-y)
ifeq ($(CONFIG_CPU_32v3),y)
diff --git a/arch/arm/lib/clear_user.S b/arch/arm/lib/clear_user.S
index 4d6bc71231f3..844f56785ebc 100644
--- a/arch/arm/lib/clear_user.S
+++ b/arch/arm/lib/clear_user.S
@@ -18,7 +18,8 @@
* : sz - number of bytes to clear
* Returns : number of bytes NOT cleared
*/
-ENTRY(__clear_user)
+ENTRY(__clear_user_std)
+WEAK(__clear_user)
stmfd sp!, {r1, lr}
mov r2, #0
cmp r1, #4
diff --git a/arch/arm/lib/copy_to_user.S b/arch/arm/lib/copy_to_user.S
index 22f968bbdffd..878820f0a320 100644
--- a/arch/arm/lib/copy_to_user.S
+++ b/arch/arm/lib/copy_to_user.S
@@ -86,7 +86,8 @@
.text
-ENTRY(__copy_to_user)
+ENTRY(__copy_to_user_std)
+WEAK(__copy_to_user)
#include "copy_template.S"
diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
new file mode 100644
index 000000000000..6b967ffb6552
--- /dev/null
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -0,0 +1,228 @@
+/*
+ * linux/arch/arm/lib/uaccess_with_memcpy.c
+ *
+ * Written by: Lennert Buytenhek and Nicolas Pitre
+ * Copyright (C) 2009 Marvell Semiconductor
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/uaccess.h>
+#include <linux/rwsem.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/hardirq.h> /* for in_atomic() */
+#include <asm/current.h>
+#include <asm/page.h>
+
+static int
+pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
+{
+ unsigned long addr = (unsigned long)_addr;
+ pgd_t *pgd;
+ pmd_t *pmd;
+ pte_t *pte;
+ spinlock_t *ptl;
+
+ pgd = pgd_offset(current->mm, addr);
+ if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
+ return 0;
+
+ pmd = pmd_offset(pgd, addr);
+ if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd)))
+ return 0;
+
+ pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
+ if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
+ !pte_write(*pte) || !pte_dirty(*pte))) {
+ pte_unmap_unlock(pte, ptl);
+ return 0;
+ }
+
+ *ptep = pte;
+ *ptlp = ptl;
+
+ return 1;
+}
+
+static unsigned long noinline
+__copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
+{
+ int atomic;
+
+ if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
+ memcpy((void *)to, from, n);
+ return 0;
+ }
+
+ /* the mmap semaphore is taken only if not in an atomic context */
+ atomic = in_atomic();
+
+ if (!atomic)
+ down_read(&current->mm->mmap_sem);
+ while (n) {
+ pte_t *pte;
+ spinlock_t *ptl;
+ int tocopy;
+
+ while (!pin_page_for_write(to, &pte, &ptl)) {
+ if (!atomic)
+ up_read(&current->mm->mmap_sem);
+ if (__put_user(0, (char __user *)to))
+ goto out;
+ if (!atomic)
+ down_read(&current->mm->mmap_sem);
+ }
+
+ tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
+ if (tocopy > n)
+ tocopy = n;
+
+ memcpy((void *)to, from, tocopy);
+ to += tocopy;
+ from += tocopy;
+ n -= tocopy;
+
+ pte_unmap_unlock(pte, ptl);
+ }
+ if (!atomic)
+ up_read(&current->mm->mmap_sem);
+
+out:
+ return n;
+}
+
+unsigned long
+__copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+ /*
+ * This test is stubbed out of the main function above to keep
+ * the overhead for small copies low by avoiding a large
+ * register dump on the stack just to reload them right away.
+ * With frame pointer disabled, tail call optimization kicks in
+ * as well making this test almost invisible.
+ */
+ if (n < 64)
+ return __copy_to_user_std(to, from, n);
+ return __copy_to_user_memcpy(to, from, n);
+}
+
+static unsigned long noinline
+__clear_user_memset(void __user *addr, unsigned long n)
+{
+ if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
+ memset((void *)addr, 0, n);
+ return 0;
+ }
+
+ down_read(&current->mm->mmap_sem);
+ while (n) {
+ pte_t *pte;
+ spinlock_t *ptl;
+ int tocopy;
+
+ while (!pin_page_for_write(addr, &pte, &ptl)) {
+ up_read(&current->mm->mmap_sem);
+ if (__put_user(0, (char __user *)addr))
+ goto out;
+ down_read(&current->mm->mmap_sem);
+ }
+
+ tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
+ if (tocopy > n)
+ tocopy = n;
+
+ memset((void *)addr, 0, tocopy);
+ addr += tocopy;
+ n -= tocopy;
+
+ pte_unmap_unlock(pte, ptl);
+ }
+ up_read(&current->mm->mmap_sem);
+
+out:
+ return n;
+}
+
+unsigned long __clear_user(void __user *addr, unsigned long n)
+{
+ /* See rational for this in __copy_to_user() above. */
+ if (n < 64)
+ return __clear_user_std(addr, n);
+ return __clear_user_memset(addr, n);
+}
+
+#if 0
+
+/*
+ * This code is disabled by default, but kept around in case the chosen
+ * thresholds need to be revalidated. Some overhead (small but still)
+ * would be implied by a runtime determined variable threshold, and
+ * so far the measurement on concerned targets didn't show a worthwhile
+ * variation.
+ *
+ * Note that a fairly precise sched_clock() implementation is needed
+ * for results to make some sense.
+ */
+
+#include <linux/vmalloc.h>
+
+static int __init test_size_treshold(void)
+{
+ struct page *src_page, *dst_page;
+ void *user_ptr, *kernel_ptr;
+ unsigned long long t0, t1, t2;
+ int size, ret;
+
+ ret = -ENOMEM;
+ src_page = alloc_page(GFP_KERNEL);
+ if (!src_page)
+ goto no_src;
+ dst_page = alloc_page(GFP_KERNEL);
+ if (!dst_page)
+ goto no_dst;
+ kernel_ptr = page_address(src_page);
+ user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010));
+ if (!user_ptr)
+ goto no_vmap;
+
+ /* warm up the src page dcache */
+ ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE);
+
+ for (size = PAGE_SIZE; size >= 4; size /= 2) {
+ t0 = sched_clock();
+ ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size);
+ t1 = sched_clock();
+ ret |= __copy_to_user_std(user_ptr, kernel_ptr, size);
+ t2 = sched_clock();
+ printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
+ }
+
+ for (size = PAGE_SIZE; size >= 4; size /= 2) {
+ t0 = sched_clock();
+ ret |= __clear_user_memset(user_ptr, size);
+ t1 = sched_clock();
+ ret |= __clear_user_std(user_ptr, size);
+ t2 = sched_clock();
+ printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
+ }
+
+ if (ret)
+ ret = -EFAULT;
+
+ vunmap(user_ptr);
+no_vmap:
+ put_page(dst_page);
+no_dst:
+ put_page(src_page);
+no_src:
+ return ret;
+}
+
+subsys_initcall(test_size_treshold);
+
+#endif