initial commit of lk (little kernel) project
diff --git a/lib/libc/string/arch/arm/memset.S b/lib/libc/string/arch/arm/memset.S
new file mode 100644
index 0000000..b31d053
--- /dev/null
+++ b/lib/libc/string/arch/arm/memset.S
@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2008 Travis Geiselbrecht
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <asm.h>
+#include <arch/arm/cores.h>
+
+.text
+.align 2
+
+/* void bzero(void *s, size_t n); */
+FUNCTION(bzero)
+ mov r2, r1
+ mov r1, #0
+
+/* void *memset(void *s, int c, size_t n); */
+FUNCTION(memset)
+ // check for zero length
+ cmp r2, #0
+ bxeq lr
+
+ // save the original pointer
+ mov r12, r0
+
+ // short memsets aren't worth optimizing
+ cmp r2, #(32 + 16)
+ blt .L_bytewise
+
+ // fill a 32 bit register with the 8 bit value
+ and r1, r1, #0xff
+ orr r1, r1, r1, lsl #8
+ orr r1, r1, r1, lsl #16
+
+ // check for 16 byte alignment
+ tst r0, #15
+ bne .L_not16bytealigned
+
+.L_bigset:
+ // dump some registers to make space for our values
+ stmfd sp!, { r4-r5 }
+
+ // fill a bunch of registers with the set value
+ mov r3, r1
+ mov r4, r1
+ mov r5, r1
+
+ // prepare the count register so we can avoid an extra compare
+ sub r2, r2, #32
+
+ // 32 bytes at a time
+.L_bigset_loop:
+ stmia r0!, { r1, r3, r4, r5 }
+ subs r2, r2, #32
+ stmia r0!, { r1, r3, r4, r5 }
+ bge .L_bigset_loop
+
+ // restore our dumped registers
+ ldmfd sp!, { r4-r5 }
+
+ // see if we're done
+ adds r2, r2, #32
+ beq .L_done
+
+.L_bytewise:
+ // bytewise memset
+ subs r2, r2, #1
+ strb r1, [r0], #1
+ bgt .L_bytewise
+
+.L_done:
+ // restore the base pointer as return value
+ mov r0, r12
+ bx lr
+
+.L_not16bytealigned:
+ // dst is not 16 byte aligned, so we will set up to 15 bytes to get it aligned.
+
+ // set the condition flags based on the alignment.
+ lsl r3, r0, #28
+ rsb r3, r3, #0
+ msr CPSR_f, r3 // move into NZCV fields in CPSR
+
+ // move as many bytes as necessary to get the dst aligned
+ strvsb r1, [r0], #1 // V set
+ strcsh r1, [r0], #2 // C set
+ streq r1, [r0], #4 // Z set
+ strmi r1, [r0], #4 // N set
+ strmi r1, [r0], #4 // N set
+
+ // fix the remaining len
+ sub r2, r2, r3, lsr #28
+
+ // do the large memset
+ b .L_bigset
+