semihosting tests: initial commit

Usermode tests work; system emulation tests work for A32 at least.

Note: includes a third-party 3-clause-BSD printf implementation.

The semihosting.[ch] and string.[ch] files are from the Linaro
boot-wrapper.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

13 files changed, 985 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..35c8aa7
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,56 @@
+# Makefile for semihosting tests
+#
+# Copyright (c) 2015 Linaro Limited
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name of Linaro Limited nor the names of its
+#    contributors may be used to endorse or promote products derived
+#    from this software without specific prior written permission.
+#
+#
+# We have several orthogonal cases we'd like to test:
+# A32 vs T32 vs A64
+# usermode vs system
+# gdb syscalls vs normal
+#
+# For the moment this is only testing usermode.
+
+A32GCC := arm-linux-gnueabihf-gcc -marm
+T32GCC := arm-linux-gnueabihf-gcc -mthumb
+A64GCC := aarch64-linux-gnu-gcc
+
+A32LD := arm-linux-gnueabihf-ld
+
+all: usertest-a32 usertest-a64 usertest-t32
+
+usertest-srcs = usertest.c semihosting.c semicall.S
+
+systest-srcs = start.S string.c printf/printf.c $(usertest-srcs)
+
+usertest-a32: $(usertest-srcs)
+	$(A32GCC) --static -o $@ $^
+
+usertest-t32: $(usertest-srcs)
+	$(T32GCC) --static -o $@ $^
+
+usertest-a64: $(usertest-srcs)
+	$(A64GCC) --static -o $@ $^
+
+systest-a32.axf: $(systest-srcs)
+	$(A32GCC) -nostdlib -o $@ $^ -lgcc -Xlinker --script=baremetal.lds
+
+systest-t32.axf: $(systest-srcs)
+	$(T32GCC) -nostdlib -o $@ $^ -Xlinker --script=baremetal.lds
+
+systest-a64.axf: $(systest-srcs)
+	$(A64GCC) -nostdlib -o $@ $^ -lgcc -Xlinker --script=baremetal.lds
+
diff --git a/baremetal.lds b/baremetal.lds
new file mode 100644
index 0000000..6d98672
--- /dev/null
+++ b/baremetal.lds
@@ -0,0 +1,25 @@
+/*
+ * baremetal.lds : simple linker script for baremetal test cases
+ *
+ * Copyright (C) 2015 Linaro Limited. All rights reserved.
+ * 
+ * Memory layout is for the virt board which puts RAM at 0x40000000
+ *
+ * Use:
+ *  $(LD) -o image.axf input.o --script=baremetal.lds
+ */
+
+OUTPUT_FORMAT("elf32-littlearm")
+OUTPUT_ARCH(arm)
+TARGET(binary)
+RAMSTART = 0x40000000;
+STACKTOP = 0x40200000;
+SECTIONS
+{
+ . = RAMSTART;
+ .text : { *(.text) }
+ .data : { *(.data) }
+ .bss : { *(.bss) }
+ . = STACKTOP;
+ stacktop = .;
+}
diff --git a/printf/README b/printf/README
new file mode 100644
index 0000000..15478d9
--- /dev/null
+++ b/printf/README
@@ -0,0 +1,2 @@
+printf implementation from http://www.sparetimelabs.com/tinyprintf/tinyprintf.php
+under 3-clause BSD
diff --git a/printf/printf.c b/printf/printf.c
new file mode 100755
index 0000000..4db1289
--- /dev/null
+++ b/printf/printf.c
@@ -0,0 +1,245 @@
+/*

+ * Copyright (c) 2004,2012 Kustaa Nyholm / SpareTimeLabs

+ *

+ * All rights reserved.

+ *

+ * Redistribution and use in source and binary forms, with or without modification, 

+ * are permitted provided that the following conditions are met:

+ *

+ * Redistributions of source code must retain the above copyright notice, this list 

+ * of conditions and the following disclaimer.

+ * 

+ * Redistributions in binary form must reproduce the above copyright notice, this 

+ * list of conditions and the following disclaimer in the documentation and/or other

+ * materials provided with the distribution.

+ *  

+ * Neither the name of the Kustaa Nyholm or SpareTimeLabs nor the names of its 

+ * contributors may be used to endorse or promote products derived from this software 

+ * without specific prior written permission.

+ * 

+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 

+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 

+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 

+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 

+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 

+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 

+ * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 

+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 

+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

+ * OF SUCH DAMAGE.

+ */

+

+#include "printf.h"

+

+typedef void (*putcf) (void*,char);

+static putcf stdout_putf;

+static void* stdout_putp;

+

+

+#ifdef PRINTF_LONG_SUPPORT

+

+static void uli2a(unsigned long int num, unsigned int base, int uc,char * bf)

+	{

+	int n=0;

+	unsigned int d=1;

+	while (num/d >= base)

+		d*=base;		 

+	while (d!=0) {

+		int dgt = num / d;

+		num%=d;

+		d/=base;

+		if (n || dgt>0|| d==0) {

+			*bf++ = dgt+(dgt<10 ? '0' : (uc ? 'A' : 'a')-10);

+			++n;

+			}

+		}

+	*bf=0;

+	}

+

+static void li2a (long num, char * bf)

+	{

+	if (num<0) {

+		num=-num;

+		*bf++ = '-';

+		}

+	uli2a(num,10,0,bf);

+	}

+

+#endif

+

+static void ui2a(unsigned int num, unsigned int base, int uc,char * bf)

+	{

+	int n=0;

+	unsigned int d=1;

+	while (num/d >= base)

+		d*=base;		

+	while (d!=0) {

+		int dgt = num / d;

+		num%= d;

+		d/=base;

+		if (n || dgt>0 || d==0) {

+			*bf++ = dgt+(dgt<10 ? '0' : (uc ? 'A' : 'a')-10);

+			++n;

+			}

+		}

+	*bf=0;

+	}

+

+static void i2a (int num, char * bf)

+	{

+	if (num<0) {

+		num=-num;

+		*bf++ = '-';

+		}

+	ui2a(num,10,0,bf);

+	}

+

+static int a2d(char ch)

+	{

+	if (ch>='0' && ch<='9') 

+		return ch-'0';

+	else if (ch>='a' && ch<='f')

+		return ch-'a'+10;

+	else if (ch>='A' && ch<='F')

+		return ch-'A'+10;

+	else return -1;

+	}

+

+static char a2i(char ch, char** src,int base,int* nump)

+	{

+	char* p= *src;

+	int num=0;

+	int digit;

+	while ((digit=a2d(ch))>=0) {

+		if (digit>base) break;

+		num=num*base+digit;

+		ch=*p++;

+		}

+	*src=p;

+	*nump=num;

+	return ch;

+	}

+

+static void putchw(void* putp,putcf putf,int n, char z, char* bf)

+	{

+	char fc=z? '0' : ' ';

+	char ch;

+	char* p=bf;

+	while (*p++ && n > 0)

+		n--;

+	while (n-- > 0) 

+		putf(putp,fc);

+	while ((ch= *bf++))

+		putf(putp,ch);

+	}

+

+void tfp_format(void* putp,putcf putf,char *fmt, va_list va)

+	{

+	char bf[12];

+    

+	char ch;

+

+

+	while ((ch=*(fmt++))) {

+		if (ch!='%') 

+			putf(putp,ch);

+		else {

+			char lz=0;

+#ifdef 	PRINTF_LONG_SUPPORT

+			char lng=0;

+#endif

+			int w=0;

+			ch=*(fmt++);

+			if (ch=='0') {

+				ch=*(fmt++);

+				lz=1;

+				}

+			if (ch>='0' && ch<='9') {

+				ch=a2i(ch,&fmt,10,&w);

+				}

+#ifdef 	PRINTF_LONG_SUPPORT

+			if (ch=='l') {

+				ch=*(fmt++);

+				lng=1;

+			}

+#endif

+			switch (ch) {

+				case 0: 

+					goto abort;

+				case 'u' : {

+#ifdef 	PRINTF_LONG_SUPPORT

+					if (lng)

+						uli2a(va_arg(va, unsigned long int),10,0,bf);

+					else

+#endif

+					ui2a(va_arg(va, unsigned int),10,0,bf);

+					putchw(putp,putf,w,lz,bf);

+					break;

+					}

+				case 'd' :  {

+#ifdef 	PRINTF_LONG_SUPPORT

+					if (lng)

+						li2a(va_arg(va, unsigned long int),bf);

+					else

+#endif

+					i2a(va_arg(va, int),bf);

+					putchw(putp,putf,w,lz,bf);

+					break;

+					}

+				case 'x': case 'X' : 

+#ifdef 	PRINTF_LONG_SUPPORT

+					if (lng)

+						uli2a(va_arg(va, unsigned long int),16,(ch=='X'),bf);

+					else

+#endif

+					ui2a(va_arg(va, unsigned int),16,(ch=='X'),bf);

+					putchw(putp,putf,w,lz,bf);

+					break;

+				case 'c' : 

+					putf(putp,(char)(va_arg(va, int)));

+					break;

+				case 's' : 

+					putchw(putp,putf,w,0,va_arg(va, char*));

+					break;

+				case '%' :

+					putf(putp,ch);

+				default:

+					break;

+				}

+			}

+		}

+	abort:;

+	}

+

+

+void init_printf(void* putp,void (*putf) (void*,char))

+	{

+	stdout_putf=putf;

+	stdout_putp=putp;

+	}

+

+void tfp_printf(char *fmt, ...)

+	{

+	va_list va;

+	va_start(va,fmt);

+	tfp_format(stdout_putp,stdout_putf,fmt,va);

+	va_end(va);

+	}

+

+static void putcp(void* p,char c)

+	{

+	*(*((char**)p))++ = c;

+	}

+

+

+

+void tfp_sprintf(char* s,char *fmt, ...)

+	{

+	va_list va;

+	va_start(va,fmt);

+	tfp_format(&s,putcp,fmt,va);

+	putcp(&s,0);

+	va_end(va);

+	}

+

+

diff --git a/printf/printf.h b/printf/printf.h
new file mode 100755
index 0000000..3790e72
--- /dev/null
+++ b/printf/printf.h
@@ -0,0 +1,124 @@
+/*

+File: printf.h

+ 

+Copyright (c) 2004,2012 Kustaa Nyholm / SpareTimeLabs

+

+All rights reserved.

+

+Redistribution and use in source and binary forms, with or without modification, 

+are permitted provided that the following conditions are met:

+

+Redistributions of source code must retain the above copyright notice, this list 

+of conditions and the following disclaimer.

+

+Redistributions in binary form must reproduce the above copyright notice, this 

+list of conditions and the following disclaimer in the documentation and/or other

+materials provided with the distribution.

+ 

+Neither the name of the Kustaa Nyholm or SpareTimeLabs nor the names of its 

+contributors may be used to endorse or promote products derived from this software 

+without specific prior written permission.

+

+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 

+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 

+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 

+IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 

+INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 

+NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 

+OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 

+WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 

+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

+OF SUCH DAMAGE.

+

+----------------------------------------------------------------------

+

+This library is realy just two files: 'printf.h' and 'printf.c'.

+

+They provide a simple and small (+200 loc) printf functionality to 

+be used in embedded systems.

+

+I've found them so usefull in debugging that I do not bother with a 

+debugger at all.

+

+They are distributed in source form, so to use them, just compile them 

+into your project. 

+

+Two printf variants are provided: printf and sprintf. 

+

+The formats supported by this implementation are: 'd' 'u' 'c' 's' 'x' 'X'.

+

+Zero padding and field width are also supported.

+

+If the library is compiled with 'PRINTF_SUPPORT_LONG' defined then the 

+long specifier is also

+supported. Note that this will pull in some long math routines (pun intended!)

+and thus make your executable noticably longer.

+

+The memory foot print of course depends on the target cpu, compiler and 

+compiler options, but a rough guestimate (based on a H8S target) is about 

+1.4 kB for code and some twenty 'int's and 'char's, say 60 bytes of stack space. 

+Not too bad. Your milage may vary. By hacking the source code you can 

+get rid of some hunred bytes, I'm sure, but personally I feel the balance of 

+functionality and flexibility versus  code size is close to optimal for

+many embedded systems.

+

+To use the printf you need to supply your own character output function, 

+something like :

+

+void putc ( void* p, char c)

+	{

+	while (!SERIAL_PORT_EMPTY) ;

+	SERIAL_PORT_TX_REGISTER = c;

+	}

+

+Before you can call printf you need to initialize it to use your 

+character output function with something like:

+

+init_printf(NULL,putc);

+

+Notice the 'NULL' in 'init_printf' and the parameter 'void* p' in 'putc', 

+the NULL (or any pointer) you pass into the 'init_printf' will eventually be 

+passed to your 'putc' routine. This allows you to pass some storage space (or 

+anything realy) to the character output function, if necessary. 

+This is not often needed but it was implemented like that because it made 

+implementing the sprintf function so neat (look at the source code).

+

+The code is re-entrant, except for the 'init_printf' function, so it 

+is safe to call it from interupts too, although this may result in mixed output. 

+If you rely on re-entrancy, take care that your 'putc' function is re-entrant!

+

+The printf and sprintf functions are actually macros that translate to 

+'tfp_printf' and 'tfp_sprintf'. This makes it possible

+to use them along with 'stdio.h' printf's in a single source file. 

+You just need to undef the names before you include the 'stdio.h'.

+Note that these are not function like macros, so if you have variables

+or struct members with these names, things will explode in your face.

+Without variadic macros this is the best we can do to wrap these

+fucnction. If it is a problem just give up the macros and use the

+functions directly or rename them.

+

+For further details see source code.

+

+regs Kusti, 23.10.2004

+*/

+

+

+#ifndef __TFP_PRINTF__

+#define __TFP_PRINTF__

+

+#include <stdarg.h>

+

+void init_printf(void* putp,void (*putf) (void*,char));

+

+void tfp_printf(char *fmt, ...);

+void tfp_sprintf(char* s,char *fmt, ...);

+

+void tfp_format(void* putp,void (*putf) (void*,char),char *fmt, va_list va);

+

+#define printf tfp_printf 

+#define sprintf tfp_sprintf 

+

+#endif

+

+

+

diff --git a/semicall.S b/semicall.S
new file mode 100644
index 0000000..6634594
--- /dev/null
+++ b/semicall.S
@@ -0,0 +1,45 @@
+/*
+ * semicall.S - assembly stub for making semihosting call
+ *
+ * Copyright (c) 2015 Linaro Limited
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of Linaro Limited nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ */
+
+#ifndef __aarch64__
+        .syntax unified
+#endif
+
+        .text
+
+#if defined(__thumb__)
+        .thumb
+#endif
+
+        .globl __semi_call
+__semi_call:
+#if defined(__aarch64__)
+        hlt 0xf000
+        ret
+#else
+
+#if defined(__thumb__)
+        svc 0xab
+#else
+        svc 0x123456
+#endif
+        bx lr
+
+#endif
diff --git a/semihosting.c b/semihosting.c
new file mode 100644
index 0000000..ee13273
--- /dev/null
+++ b/semihosting.c
@@ -0,0 +1,174 @@
+/*
+ * Copyright (c) 2012 Linaro Limited
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of Linaro Limited nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ */
+
+#include <inttypes.h>
+#include <string.h>
+#include "semihosting.h"
+
+int semi_open(char const *filename, int mode)
+{
+    struct {
+        char const *filename;
+        intptr_t mode;
+        intptr_t filename_length;
+    } args;
+
+    args.filename = filename;
+    args.mode = mode;
+    args.filename_length = strlen(filename);
+
+    return __semi_call(SYS_OPEN, &args);
+}
+
+int semi_close(int fd)
+{
+    struct {
+        intptr_t fd;
+    } args;
+
+    args.fd = fd;
+    return __semi_call(SYS_CLOSE, &args);
+}
+
+int semi_write0(char const *string)
+{
+    return __semi_call(SYS_WRITE0, string);
+}
+
+void semi_writec(char c)
+{
+    __semi_call(SYS_WRITEC, &c);
+}
+
+int semi_read(int fd, char *buffer, int length)
+{
+    struct {
+        intptr_t fd;
+        char *buffer;
+        intptr_t length;
+    } args;
+
+    args.fd = fd;
+    args.buffer = buffer;
+    args.length = length;
+
+    return __semi_call(SYS_READ, &args);
+}
+
+int semi_flen(int fd)
+{
+    struct {
+        intptr_t fd;
+    } args;
+
+    args.fd = fd;
+    return __semi_call(SYS_FLEN, &args);
+}
+
+int semi_get_cmdline(char *buffer, int size, int *length)
+{
+    int result;
+    struct {
+        char *buffer;
+        intptr_t size;
+    } args;
+
+    args.buffer = buffer;
+    args.size = size;
+
+    result = __semi_call(SYS_GET_CMDLINE, &args);
+    if(result)
+        return result;
+
+    if(length)
+        *length = args.size;
+
+    return 0;
+}
+
+int semi_reportexc(int reason, int subcode)
+{
+#ifdef __aarch64__
+    /* The A64 interface to this call takes an arg block,
+     * whereas the A32/T32 interface just takes the reason
+     * code in a register.
+     */
+    struct {
+        intptr_t reason;
+        intptr_t subcode;
+    } args;
+
+    args.reason = reason;
+    args.subcode = subcode;
+    return __semi_call(SYS_REPORTEXC, &args);
+#else
+    return __semi_call(SYS_REPORTEXC, (void *)reason);
+#endif
+}
+
+void semi_exit(int subcode)
+{
+    semi_reportexc(REPORTEXC_REASON_APP_EXIT, subcode);
+    while(1); /* should not be reached */
+}
+
+void semi_fatal(char const *message)
+{
+    semi_write0(message);
+    semi_exit(1);
+}
+
+int semi_load_file(void **dest, unsigned *size, char const *filename)
+{
+    int result = -1;	/* fail by default */
+    int fd = -1;
+    int filesize;
+
+    fd = semi_open(filename, OPEN_RDONLY);
+    if(fd == -1) {
+        semi_write0("Cannot open file: ");
+        goto out;
+    }
+
+    filesize = semi_flen(fd);
+    if(filesize == -1) {
+        semi_write0("Cannot get file size for: ");
+        goto out;
+    }
+
+    if(semi_read(fd, *dest, filesize)) {
+        semi_write0("Could not read: ");
+        goto out;
+    }
+
+    result = 0;	/* success */
+    *dest = (char *)*dest + filesize;
+
+out:
+    if(fd != -1)
+        semi_close(fd);
+
+    if(result) {	/* print context for the error message */
+        semi_write0(filename);
+        semi_write0("\n");
+    } else
+        if(size)
+            *size = filesize;
+
+    return result;
+}
diff --git a/semihosting.h b/semihosting.h
new file mode 100644
index 0000000..dc1751f
--- /dev/null
+++ b/semihosting.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2012 Linaro Limited
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of Linaro Limited nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ */
+
+#ifndef SEMIHOSTING_H
+#define SEMIHOSTING_H
+
+#define SYS_OPEN	1
+#define OPEN_RDONLY	1
+#define SYS_CLOSE	2
+#define SYS_WRITEC	3
+#define SYS_WRITE0	4
+#define SYS_READ	6
+#define SYS_FLEN	0x0C
+#define SYS_GET_CMDLINE	0x15
+#define SYS_REPORTEXC	0x18
+#define REPORTEXC_REASON_APP_EXIT 0x20026
+#define SEMIHOSTING_SVC	0x123456	/* SVC comment field for semihosting */
+
+#ifndef __ASSEMBLER__
+
+int __semi_call(int id, ...);
+int semi_open(char const *filename, int mode);
+int semi_close(int fd);
+int semi_write0(char const *string);
+void semi_writec(char c);
+int semi_read(int fd, char *buffer, int length);
+int semi_flen(int fd);
+int semi_get_cmdline(char *buffer, int size, int *length);
+int semi_reportexc(int reason, int subcode);
+void semi_fatal(char const *message);
+void semi_exit(int subcode);
+/* semi_load_file: *dest is advanced to point to the end of the loaded data */
+int semi_load_file(void **dest, unsigned *size, char const *filename);
+
+#endif /* ! __ASSEMBLER__ */
+
+#endif /* ! SEMIHOSTING_H */
diff --git a/start.S b/start.S
new file mode 100644
index 0000000..5a1db58
--- /dev/null
+++ b/start.S
@@ -0,0 +1,38 @@
+/*
+ * start.S - assembly code for startup on baremetal tests
+ *
+ * Copyright (c) 2015 Linaro Limited
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of Linaro Limited nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ */
+
+#ifndef __aarch64__
+        .syntax unified
+#endif
+
+        .text
+
+        .globl start
+start:
+        # We assume uniprocessor.
+        # TODO: enable floating point??
+
+        # Set up a stack
+        ldr sp, =stacktop
+        bl main
+        bl semi_exit
+        # not reached
+1:      b 1b
+
diff --git a/string.c b/string.c
new file mode 100644
index 0000000..a807baa
--- /dev/null
+++ b/string.c
@@ -0,0 +1,137 @@
+#include <string.h>
+
+static void *__memmove_down(void *__dest, __const void *__src, size_t __n)
+{
+	unsigned char *d = (unsigned char *)__dest, *s = (unsigned char *)__src;
+
+	while (__n--)
+		*d++ = *s++;
+
+	return __dest;
+}
+
+static void *__memmove_up(void *__dest, __const void *__src, size_t __n)
+{
+	unsigned char *d = (unsigned char *)__dest + __n - 1, *s = (unsigned char *)__src + __n - 1;
+
+	while (__n--)
+		*d-- = *s--;
+
+	return __dest;
+}
+
+void *(memcpy)(void *__dest, __const void *__src, size_t __n)
+{
+	return __memmove_down(__dest, __src, __n);
+}
+
+void *(memmove)(void *__dest, __const void *__src, size_t __n)
+{
+	if(__dest > __src)
+		return __memmove_up(__dest, __src, __n);
+	else
+		return __memmove_down(__dest, __src, __n);
+}
+
+void *(memchr)(void const *s, int c, size_t n)
+{
+	unsigned char const *_s = (unsigned char const *)s;
+
+	while(n && *_s != c) {
+		++_s;
+		--n;
+	}
+
+	if(n)
+		return (void *)_s;	/* the C library casts const away */
+	else
+		return (void *)0;
+}
+
+size_t (strlen)(const char *s)
+{
+	const char *sc = s;
+
+	while (*sc != '\0')
+		sc++;
+	return sc - s;
+}
+
+void *(memset)(void *s, int c, size_t count)
+{
+	char *xs = s;
+	while (count--)
+		*xs++ = c;
+	return s;
+}
+
+int (memcmp)(void const *p1, void const *p2, size_t n)
+{
+	unsigned char const *_p1 = p1;
+	unsigned char const *_p2 = p2;
+
+	while(n--) {
+		if(*_p1 < *_p2)
+			return -1;
+		else if(*_p1 > *_p2)
+			return 1;
+
+		++_p1;
+		++_p2;
+	}
+
+	return 0;
+}
+
+int (strcmp)(char const *s1, char const *s2)
+{
+	while(*s1 && *s2) {
+		if(*s1 < *s2)
+			return -1;
+		else if(*s1 > *s2)
+			return 1;
+
+		++s1;
+		++s2;
+	}
+
+	if(!*s1 && !*s2)
+		return 0;
+	else if(!*s1)
+		return -1;
+	else
+		return 1;
+}
+
+int (strncmp)(char const *s1, char const *s2, size_t n)
+{
+	while(*s1 && *s2 && n--) {
+		if(*s1 < *s2)
+			return -1;
+		else if(*s1 > *s2)
+			return 1;
+
+		++s1;
+		++s2;
+	}
+
+	if(n == 0 || (!*s1 && !*s2))
+		return 0;
+	else if(!*s1)
+		return -1;
+	else
+		return 1;
+}
+
+char *(strchr)(char const *s, int c)
+{
+	unsigned char const *_s = (unsigned char const *)s;
+
+	while(*_s && *_s != c)
+		++_s;
+
+	if(*_s)
+		return (char *)_s;	/* the C library casts const away */
+	else
+		return (char *)0;
+}
diff --git a/string.h b/string.h
new file mode 100644
index 0000000..f1aebdf
--- /dev/null
+++ b/string.h
@@ -0,0 +1,16 @@
+#ifndef STRING_H
+#define STRING_H
+
+#include <stddef.h>
+
+extern void *(memcpy)(void *__dest, __const void *__src, size_t __n);
+extern void *(memmove)(void *__dest, __const void *__src, size_t __n);
+extern void *(memchr)(void const *s, int c, size_t n);
+extern size_t (strlen)(const char *s);
+extern void *(memset)(void *s, int c, size_t count);
+extern int (memcmp)(void const *p1, void const *p2, size_t n);
+extern int (strcmp)(char const *s1, char const *s2);
+extern int (strncmp)(char const *s1, char const *s2, size_t n);
+extern char *(strchr)(char const *s, int c);
+
+#endif
diff --git a/testdata.txt b/testdata.txt
new file mode 100644
index 0000000..4a422bc
--- /dev/null
+++ b/testdata.txt
@@ -0,0 +1,2 @@
+Small file of text data for test.
+Note that this file must not be longer than the buffer used to read it in the test code...
diff --git a/usertest.c b/usertest.c
new file mode 100644
index 0000000..16ef0fe
--- /dev/null
+++ b/usertest.c
@@ -0,0 +1,69 @@
+/*
+ * usertest.c -- top level test file for usermode tests
+ *
+ * Copyright (c) 2015 Linaro Limited
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name of Linaro Limited nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ */
+
+#include <stdio.h>
+#include "semihosting.h"
+#include "printf/printf.h"
+
+char filebuf[2048];
+
+/* This is needed by libgcc */
+int raise(int sig)
+{
+    semi_fatal("raise called (division by zero?)\n");
+}
+
+void semi_putc(void *p, char c)
+{
+    semi_writec(c);
+}
+
+int main(void)
+{
+    void *bufp;
+    unsigned int sz;
+
+    init_printf(NULL, semi_putc);
+
+    semi_write0("hello world via semi_write0\n");
+
+    semi_write0("open file test\n");
+
+    /* caution -- this will not do a length check on the buffer! */
+    bufp = filebuf;
+    if (semi_load_file(&bufp, &sz, "testdata.txt") < 0) {
+        semi_write0("semi_load_file failed!\n");
+        return 1;
+    }
+    if (sz >= sizeof(filebuf)) {
+        semi_write0("test file too big for buffer\n");
+        return 1;
+    }
+
+    filebuf[sizeof(filebuf) - 1] = 0;
+
+    printf("read %d bytes from file\n", sz);
+    semi_write0("buffer contents:\n");
+    semi_write0(filebuf);
+    semi_write0("tests complete, exiting via semihosting\n");
+
+    semi_exit(0);
+    /* not reached */
+}