1 files changed, 97 insertions, 18 deletions

diff --git a/lib/aarch32/misc_helpers.S b/lib/aarch32/misc_helpers.S
index bf4084a8..dc847995 100644
--- a/lib/aarch32/misc_helpers.S
+++ b/lib/aarch32/misc_helpers.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -34,6 +34,7 @@
 
 	.globl	smc
 	.globl	zeromem
+	.globl	zero_normalmem
 	.globl	memcpy4
 	.globl	disable_mmu_icache_secure
 	.globl	disable_mmu_secure
@@ -50,30 +51,108 @@ func smc
 endfunc smc
 
 /* -----------------------------------------------------------------------
- * void zeromem(void *mem, unsigned int length);
+ * void zeromem(void *mem, unsigned int length)
+ *
+ * Initialise a region in normal memory to 0. This functions complies with the
+ * AAPCS and can be called from C code.
  *
- * Initialise a memory region to 0.
- * The memory address and length must be 4-byte aligned.
  * -----------------------------------------------------------------------
  */
 func zeromem
-#if ASM_ASSERTION
-	tst	r0, #0x3
-	ASM_ASSERT(eq)
-	tst	r1, #0x3
-	ASM_ASSERT(eq)
-#endif
-	add	r2, r0, r1
-	mov	r1, #0
-z_loop:
-	cmp	r2, r0
-	beq	z_end
-	str	r1, [r0], #4
-	b	z_loop
-z_end:
+	/*
+	 * Readable names for registers
+	 *
+	 * Registers r0, r1 and r2 are also set by zeromem which
+	 * branches into the fallback path directly, so cursor, length and
+	 * stop_address should not be retargeted to other registers.
+	 */
+	cursor       .req r0 /* Start address and then current address */
+	length       .req r1 /* Length in bytes of the region to zero out */
+	/*
+	 * Reusing the r1 register as length is only used at the beginning of
+	 * the function.
+	 */
+	stop_address .req r1  /* Address past the last zeroed byte */
+	zeroreg1     .req r2  /* Source register filled with 0 */
+	zeroreg2     .req r3  /* Source register filled with 0 */
+	tmp	     .req r12 /* Temporary scratch register */
+
+	mov	zeroreg1, #0
+
+	/* stop_address is the address past the last to zero */
+	add	stop_address, cursor, length
+
+	/*
+	 * Length cannot be used anymore as it shares the same register with
+	 * stop_address.
+	 */
+	.unreq	length
+
+	/*
+	 * If the start address is already aligned to 8 bytes, skip this loop.
+	 */
+	tst	cursor, #(8-1)
+	beq	.Lzeromem_8bytes_aligned
+
+	/* Calculate the next address aligned to 8 bytes */
+	orr	tmp, cursor, #(8-1)
+	adds	tmp, tmp, #1
+	/* If it overflows, fallback to byte per byte zeroing */
+	beq	.Lzeromem_1byte_aligned
+	/* If the next aligned address is after the stop address, fall back */
+	cmp	tmp, stop_address
+	bhs	.Lzeromem_1byte_aligned
+
+	/* zero byte per byte */
+1:
+	strb	zeroreg1, [cursor], #1
+	cmp	cursor, tmp
+	bne	1b
+
+	/* zero 8 bytes at a time */
+.Lzeromem_8bytes_aligned:
+
+	/* Calculate the last 8 bytes aligned address. */
+	bic	tmp, stop_address, #(8-1)
+
+	cmp	cursor, tmp
+	bhs	2f
+
+	mov	zeroreg2, #0
+1:
+	stmia	cursor!, {zeroreg1, zeroreg2}
+	cmp	cursor, tmp
+	blo	1b
+2:
+
+	/* zero byte per byte */
+.Lzeromem_1byte_aligned:
+	cmp	cursor, stop_address
+	beq	2f
+1:
+	strb	zeroreg1, [cursor], #1
+	cmp	cursor, stop_address
+	bne	1b
+2:
 	bx	lr
+
+	.unreq	cursor
+	/*
+	 * length is already unreq'ed to reuse the register for another
+	 * variable.
+	 */
+	.unreq	stop_address
+	.unreq	zeroreg1
+	.unreq	zeroreg2
+	.unreq	tmp
 endfunc zeromem
 
+/*
+ * AArch32 does not have special ways of zeroing normal memory as AArch64 does
+ * using the DC ZVA instruction, so we just alias zero_normalmem to zeromem.
+ */
+.equ	zero_normalmem, zeromem
+
 /* --------------------------------------------------------------------------
  * void memcpy4(void *dest, const void *src, unsigned int length)
  *