Introduce __fill_user() and kill __bzero() [take #2]

Currently memset() is used to fill a user space area (clear_user) or kernel one (memset). These two functions don't have the same prototype, the former returning the number of bytes not copied and the latter returning the start address of the area to clear. This forces memset() to actually returns two values in an unconventional way ie the number of bytes not copied is given by $a2. Therefore clear_user() needs to call memset() using inline assembly.

Instead this patch creates __fill_user() which is the same as memset() except it always returns the number of bytes not copied. This simplify clear_user() and makes its definition saner.

Also an out of line version of memset is given because gcc generates some calls to it since builtin functions have been disabled. It allows assembly code to call it too.

Eventually __bzero() has been removed because it's not part of the Linux uaccess API. And the nano-optimization it brings is not worthing.

---

Thimeo,

I put the out of line version of memset in kernel/mips_ksym.c. I haven't found a better place. But if you really think we should create a lib/memset.c and rename lib/memset.S into lib/fill_user.S, I can change it.

Thanks,
Franck

 arch/mips/kernel/mips_ksyms.c |   13 +++++++++++--
 arch/mips/lib/csum_partial.S  |    2 +-
 arch/mips/lib/memcpy.S        |    2 +-
 arch/mips/lib/memset.S        |   34 +++++++++++++++++-----------------
 include/asm-mips/string.h     |    7 ++++++-
 include/asm-mips/uaccess.h    |   17 +++--------------
 6 files changed, 39 insertions(+), 36 deletions(-)

index 225755d..091275e 100644
@@ -14,7 +14,6 @@
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 
-extern void *__bzero(void *__s, size_t __count);
 extern long __strncpy_from_user_nocheck_asm(char *__to,
                                             const char *__from, long __len);
 extern long __strncpy_from_user_asm(char *__to, const char *__from,

@@ -36,9 +35,9 @@ EXPORT_SYMBOL(kernel_thread);
 /*
  * Userspace access stuff.
  */
+EXPORT_SYMBOL(__fill_user);
 EXPORT_SYMBOL(__copy_user);
 EXPORT_SYMBOL(__copy_user_inatomic);
-EXPORT_SYMBOL(__bzero);
 EXPORT_SYMBOL(__strncpy_from_user_nocheck_asm);
 EXPORT_SYMBOL(__strncpy_from_user_asm);
 EXPORT_SYMBOL(__strlen_user_nocheck_asm);

@@ -51,3 +50,13 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
 EXPORT_SYMBOL(__csum_partial_copy_user);
 
 EXPORT_SYMBOL(invalid_pte_table);
+
+/*
+ * An outline version of memset, which should be used either by gcc or
+ * by assembly code.
+ */
+void *memset(void *s, int c, __kernel_size_t len)
+{
+	__fill_user(s, c, len);
+	return s;
+}

index c0a77fe..8d3fa1e 100644
@@ -694,7 +694,7 @@ l_exc:
 	ADD	dst, t0			# compute start address in a1
 	SUB	dst, src
 	/*
-	 * Clear len bytes starting at dst.  Can't call __bzero because it
+	 * Clear len bytes starting at dst.  Can't call memset because it
 	 * might modify len.  An inefficient loop for these rare times...
 	 */
 	beqz	len, done

index a526c62..425f2c3 100644
@@ -443,7 +443,7 @@ l_exc:
 	ADD	dst, t0			# compute start address in a1
 	SUB	dst, src
 	/*
-	 * Clear len bytes starting at dst.  Can't call __bzero because it
+	 * Clear len bytes starting at dst.  Can't call memset because it
 	 * might modify len.  An inefficient loop for these rare times...
 	 */
 	beqz	len, done

index 3f8b8b3..4329811 100644
@@ -46,17 +46,19 @@
 	.endm
 
 /*
- * memset(void *s, int c, size_t n)
+ * __kernel_size_t __fill_user(void __user *s, long c, __kernel_size_t n)
  *
  * a0: start of area to clear
  * a1: char to fill with
  * a2: size of area to clear
+ *
+ * Returns the number of bytes NOT set or 0 on success.
  */
 	.set	noreorder
 	.align	5
-LEAF(memset)
+LEAF(__fill_user)
 	beqz		a1, 1f
-	 move		v0, a0			/* result */
+	 move		v0, zero		/* result */
 
 	andi		a1, 0xff		/* spread fillword */
 	LONG_SLL		t1, a1, 8

@@ -68,8 +70,6 @@ LEAF(memset)
 #endif
 	or		a1, t1
 1:
-
-FEXPORT(__bzero)
 	sltiu		t0, a2, LONGSIZE	/* very small region? */
 	bnez		t0, small_memset
 	 andi		t0, a0, LONGMASK	/* aligned? */

@@ -127,7 +127,7 @@ memset_partial:
 	EX(LONG_S_L, a1, -1(a0), last_fixup)
 #endif
 1:	jr		ra
-	 move		a2, zero
+	 nop
 
 small_memset:
 	beqz		a2, 2f

@@ -138,29 +138,29 @@ small_memset:
 	 sb		a1, -1(a0)
 
 2:	jr		ra			/* done */
-	 move		a2, zero
-	END(memset)
+	 nop
+END(__fill_user)
 
 first_fixup:
-	jr	ra
-	 nop
+	jr		ra
+	 move		v0, a2
 
 fwd_fixup:
 	PTR_L		t0, TI_TASK($28)
 	LONG_L		t0, THREAD_BUADDR(t0)
-	andi		a2, 0x3f
-	LONG_ADDU	a2, t1
+	andi		v0, a2, 0x3f
+	LONG_ADDU	v0, t1
 	jr		ra
-	 LONG_SUBU	a2, t0
+	 LONG_SUBU	v0, t0
 
 partial_fixup:
 	PTR_L		t0, TI_TASK($28)
 	LONG_L		t0, THREAD_BUADDR(t0)
-	andi		a2, LONGMASK
-	LONG_ADDU	a2, t1
+	andi		v0, a2, LONGMASK
+	LONG_ADDU	v0, t1
 	jr		ra
-	 LONG_SUBU	a2, t0
+	 LONG_SUBU	v0, t0
 
 last_fixup:
 	jr		ra
-	 andi		v1, a2, LONGMASK
+	 andi		v0, a2, LONGMASK

index 436e3ad..2bba927 100644
@@ -10,6 +10,7 @@
 #ifndef _ASM_STRING_H
 #define _ASM_STRING_H
 
+#include <asm/uaccess.h>	/* __fill_user() */
 
 /*
  * Most of the inline functions are rather naive implementations so I just

@@ -132,7 +133,11 @@ strncmp(__const__ char *__cs, __const__ char *__ct, size_t __count)
 #endif /* CONFIG_32BIT */
 
 #define __HAVE_ARCH_MEMSET
-extern void *memset(void *__s, int __c, size_t __count);
+extern inline void *memset(void *s, int c, size_t count)
+{
+	__fill_user(s, c, count);
+	return s;
+}
 
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *__to, __const__ void *__from, size_t __n);

index c30c718..8c0d226 100644
@@ -11,7 +11,6 @@
 
 #include <linux/kernel.h>
 #include <linux/errno.h>
-#include <linux/thread_info.h>
 #include <asm-generic/uaccess.h>
 
 /*

@@ -633,23 +632,13 @@ extern size_t __copy_user_inatomic(void *__to, const void *__from, size_t __n);
  * Returns number of bytes that could not be cleared.
  * On success, this will be zero.
  */
+extern __kernel_size_t __fill_user(void __user *s, long c, __kernel_size_t n);
+
 static inline __kernel_size_t
 __clear_user(void __user *addr, __kernel_size_t size)
 {
-	__kernel_size_t res;
-
 	might_sleep();
-	__asm__ __volatile__(
-		"move\t$4, %1\n\t"
-		"move\t$5, $0\n\t"
-		"move\t$6, %2\n\t"
-		__MODULE_JAL(__bzero)
-		"move\t%0, $6"
-		: "=r" (res)
-		: "r" (addr), "r" (size)
-		: "$4", "$5", "$6", __UA_t0, __UA_t1, "$31");
-
-	return res;
+	return __fill_user(addr, 0, size);
 }
 
 #define clear_user(addr,n)						\

kernel/mips_ksym.c is not a good place. Adrian `trivial' Bunk is scanning arch/ for *_ksym.c files and moving the EXPORT_SYMBOL()s to the source files they belong to.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Sigh... thanks for spotting this.

So since I've no idea where I could put this function I'll follow Thiemo's suggestion but instead of calling the new file lib/memset.c, I'll use lib/string.c since we could move or implement other stuffs in it.

Is it ok ?

Franck

lib/string.c sounds fine to me. That's where m68k and s390 implement it as well.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds