[PATCH] ARM: Move copy/clear user_page locking into implementation

Move the locking for copy_user_page() and clear_user_page() into
the implementations which require locking.  For simple memcpy/
memset based implementations, the locking is extra overhead which
is not necessary, and prevents preemption occuring.

Signed-off-by: Russell King <rmk@arm.linux.org.uk>

1 files changed, 111 insertions, 0 deletions

diff --git a/arch/arm/mm/copypage-v4mc.c b/arch/arm/mm/copypage-v4mc.c
new file mode 100644
index 000000000000..16384a7600a1
--- /dev/null
+++ b/arch/arm/mm/copypage-v4mc.c
@@ -0,0 +1,111 @@
+/*
+ *  linux/arch/arm/lib/copypage-armv4mc.S
+ *
+ *  Copyright (C) 1995-2005 Russell King
+ *
+ * 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.
+ *
+ * This handles the mini data cache, as found on SA11x0 and XScale
+ * processors.  When we copy a user page page, we map it in such a way
+ * that accesses to this page will not touch the main data cache, but
+ * will be cached in the mini data cache.  This prevents us thrashing
+ * the main data cache on page faults.
+ */
+#include <linux/init.h>
+#include <linux/mm.h>
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+/*
+ * 0xffff8000 to 0xffffffff is reserved for any ARM architecture
+ * specific hacks for copying pages efficiently.
+ */
+#define minicache_pgprot __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | \
+                                  L_PTE_CACHEABLE)
+
+#define TOP_PTE(x)      pte_offset_kernel(top_pmd, x)
+
+static DEFINE_SPINLOCK(minicache_lock);
+
+/*
+ * ARMv4 mini-dcache optimised copy_user_page
+ *
+ * We flush the destination cache lines just before we write the data into the
+ * corresponding address.  Since the Dcache is read-allocate, this removes the
+ * Dcache aliasing issue.  The writes will be forwarded to the write buffer,
+ * and merged as appropriate.
+ *
+ * Note: We rely on all ARMv4 processors implementing the "invalidate D line"
+ * instruction.  If your processor does not supply this, you have to write your
+ * own copy_user_page that does the right thing.
+ */
+static void __attribute__((naked))
+mc_copy_user_page(void *from, void *to)
+{
+        asm volatile(
+        "stmfd  sp!, {r4, lr}                   @ 2\n\
+        mov     r4, %2                          @ 1\n\
+        ldmia   %0!, {r2, r3, ip, lr}           @ 4\n\
+1:      mcr     p15, 0, %1, c7, c6, 1           @ 1   invalidate D line\n\
+        stmia   %1!, {r2, r3, ip, lr}           @ 4\n\
+        ldmia   %0!, {r2, r3, ip, lr}           @ 4+1\n\
+        stmia   %1!, {r2, r3, ip, lr}           @ 4\n\
+        ldmia   %0!, {r2, r3, ip, lr}           @ 4\n\
+        mcr     p15, 0, %1, c7, c6, 1           @ 1   invalidate D line\n\
+        stmia   %1!, {r2, r3, ip, lr}           @ 4\n\
+        ldmia   %0!, {r2, r3, ip, lr}           @ 4\n\
+        subs    r4, r4, #1                      @ 1\n\
+        stmia   %1!, {r2, r3, ip, lr}           @ 4\n\
+        ldmneia %0!, {r2, r3, ip, lr}           @ 4\n\
+        bne     1b                              @ 1\n\
+        ldmfd   sp!, {r4, pc}                   @ 3"
+        :
+        : "r" (from), "r" (to), "I" (PAGE_SIZE / 64));
+}
+
+void v4_mc_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
+{
+        spin_lock(&minicache_lock);
+
+        set_pte(TOP_PTE(COPYPAGE_MINICACHE), pfn_pte(__pa(kfrom) >> PAGE_SHIFT, minicache_pgprot));
+        flush_tlb_kernel_page(COPYPAGE_MINICACHE);
+
+        mc_copy_user_page((void *)COPYPAGE_MINICACHE, kto);
+
+        spin_unlock(&minicache_lock);
+}
+
+/*
+ * ARMv4 optimised clear_user_page
+ */
+void __attribute__((naked))
+v4_mc_clear_user_page(void *kaddr, unsigned long vaddr)
+{
+        asm volatile(
+        "str    lr, [sp, #-4]!\n\
+        mov     r1, %0                          @ 1\n\
+        mov     r2, #0                          @ 1\n\
+        mov     r3, #0                          @ 1\n\
+        mov     ip, #0                          @ 1\n\
+        mov     lr, #0                          @ 1\n\
+1:      mcr     p15, 0, r0, c7, c6, 1           @ 1   invalidate D line\n\
+        stmia   r0!, {r2, r3, ip, lr}           @ 4\n\
+        stmia   r0!, {r2, r3, ip, lr}           @ 4\n\
+        mcr     p15, 0, r0, c7, c6, 1           @ 1   invalidate D line\n\
+        stmia   r0!, {r2, r3, ip, lr}           @ 4\n\
+        stmia   r0!, {r2, r3, ip, lr}           @ 4\n\
+        subs    r1, r1, #1                      @ 1\n\
+        bne     1b                              @ 1\n\
+        ldr     pc, [sp], #4"
+        :
+        : "I" (PAGE_SIZE / 64));
+}
+
+struct cpu_user_fns v4_mc_user_fns __initdata = {
+        .cpu_clear_user_page    = v4_mc_clear_user_page, 
+        .cpu_copy_user_page     = v4_mc_copy_user_page,
+};