base-linux: add ARM support

This patch introduces a new platform 'linux_arm' for building and running
Genode/Linux on an ARM device.

Known limitations:

- libc 'setjmp()'/'longjmp()' doesn't currently save/restore floating
  point registers

Fixes #746.

base-linux/etc/specs.conf

@@ -9,8 +9,16 @@
 ifeq ($(shell uname -m),x86_64)
 SPECS ?= genode linux_x86_64 sdl
 else
+ifeq ($(shell uname -m),armv6l)
+SPECS ?= genode linux_arm sdl arm_v6
+else
+ifeq ($(shell uname -m),armv7l)
+SPECS ?= genode linux_arm sdl arm_v7a
+else
 SPECS ?= genode linux_x86_32 sdl
 endif
+endif
+endif
 
 #
 # If you want to build for the host platform,

base-linux/lib/import/import-lx_hybrid.mk

@@ -97,8 +97,12 @@ USE_HOST_LD_SCRIPT = yes
 ifeq (x86_64,$(findstring x86_64,$(SPECS)))
 CXX_LINK_OPT += -Wl,--dynamic-linker=/lib64/ld-linux-x86-64.so.2
 else
+ifeq (arm,$(findstring arm,$(SPECS)))
+CXX_LINK_OPT += -Wl,--dynamic-linker=/lib/ld-linux.so.3
+else
 CXX_LINK_OPT += -Wl,--dynamic-linker=/lib/ld-linux.so.2
 endif
+endif
 
 # because we use the host compiler's libgcc, omit the Genode toolchain's version
 LD_LIBGCC =

base-linux/lib/import/import-syscall.mk

@@ -1,9 +1,9 @@
 HOST_INC_DIR += $(dir $(call select_from_repositories,src/platform/linux_syscalls.h))
 HOST_INC_DIR += /usr/include
 
-# needed for Ubuntu 11.04
+# needed for Ubuntu >= 11.04
+HOST_INC_DIR += /usr/include/$(shell gcc -dumpmachine)
 HOST_INC_DIR += /usr/include/i386-linux-gnu
-HOST_INC_DIR += /usr/include/x86_64-linux-gnu
 
 #
 # Some header files installed on GNU/Linux test for the GNU compiler. For

base-linux/lib/mk/arm/base.mk

@@ -0,0 +1,8 @@
+include $(REP_DIR)/lib/mk/base.inc
+
+LIBS += startup cxx
+
+SRC_CC += thread.cc thread_linux.cc
+
+vpath thread.cc      $(BASE_DIR)/src/base/thread
+vpath thread_linux.cc $(REP_DIR)/src/base/thread

base-linux/lib/mk/arm/startup.mk

@@ -0,0 +1,5 @@
+LIBS += syscall
+
+include $(BASE_DIR)/lib/mk/startup.inc
+
+vpath crt0.s $(REP_DIR)/src/platform/arm

base-linux/lib/mk/arm/syscall.mk

@@ -0,0 +1,5 @@
+REQUIRES = linux arm
+SRC_S   += lx_clone.S lx_syscall.S
+
+vpath lx_clone.S   $(REP_DIR)/../base-linux/src/platform/arm
+vpath lx_syscall.S $(REP_DIR)/../base-linux/src/platform/arm

base-linux/mk/spec-linux_arm.mk

@@ -0,0 +1,25 @@
+#
+# Specifics for Linux on ARM
+#
+SPECS += linux arm
+
+REP_INC_DIR += src/platform/arm
+
+ifeq ($(shell gcc -dumpmachine),arm-linux-gnueabihf)
+CC_MARCH += -mfloat-abi=hard
+endif
+
+#
+# We need to manually add the default linker script on the command line in case
+# of standard library use. Otherwise, we were not able to extend it by the
+# context area section.
+#
+ifeq ($(USE_HOST_LD_SCRIPT),yes)
+LD_SCRIPT_STATIC = ldscripts/armelf_linux_eabi.xc
+endif
+
+#
+# Include less-specific configuration 
+#
+include $(call select_from_repositories,mk/spec-arm.mk)
+include $(call select_from_repositories,mk/spec-linux.mk)

base-linux/src/base/process/process.cc

@@ -70,7 +70,13 @@ Process::Process(Dataspace_capability   elf_data_ds_cap,
 			PERR("Dynamically linked file found, but no dynamic linker binary present");
 			return;
 		}
-		elf_data_ds_cap = _dynamic_linker_cap;
+		/*
+		 * Starting the dynamic linker directly may cause it to be loaded at the
+		 * wrong address on ARM-Linux. But since the dynamically linked
+		 * application has a dynamic linker (by default ld.lib.so) defined as its
+		 * interpreter in the ELF image, it's okay to just start the application
+		 * directly on Linux.
+		 */
 	}
 
 	/*

base-linux/src/platform/arm/crt0.s

@@ -0,0 +1,66 @@
+/*
+ * \brief   Startup code for Genode applications
+ * \author  Christian Helmuth
+ * \author  Christian Prochaska
+ * \date    2006-07-06
+ */
+
+/*
+ * Copyright (C) 2006-2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/*--- .text (program code) -------------------------*/
+	.text
+
+	.globl _start
+_start:
+
+	ldr r1,=__initial_sp
+	str sp,[r1]
+
+	/*
+	 * environ = &argv[argc + 1]
+	 * in Genode argc is always 1
+	 */
+	add sp,sp,#12
+	ldr r1,=lx_environ
+	str sp,[r1]
+
+	/* XXX Switch to our own stack.  */
+	ldr sp,=_stack_high
+
+	/* Clear the frame pointer and the link register so that stack backtraces will work. */
+	mov fp,#0
+	mov lr,#0
+
+	/* Jump into init C code */
+	b _main
+
+/*--------------------------------------------------*/
+	.data
+	.globl	__dso_handle
+__dso_handle:
+	.long	0
+
+	.globl	__initial_sp
+__initial_sp:
+	.long	0
+
+/*--- .eh_frame (exception frames) -----------------*/
+/*
+	.section .eh_frame,"aw"
+	.globl	__EH_FRAME_BEGIN__
+__EH_FRAME_BEGIN__:
+*/
+
+/*--- .bss (non-initialized data) ------------------*/
+	.bss
+	.p2align 4
+	.globl	_stack_low
+_stack_low:
+	.space	64*1024
+	.globl	_stack_high
+_stack_high:

base-linux/src/platform/arm/lx_clone.S

@@ -0,0 +1,94 @@
+/*
+ * \brief  Linux clone() binding
+ * \author Christian Prochaska
+ * \date   2012-05-05
+ *
+ * based on eglibc-2.11.3/ports/sysdeps/unix/sysv/linux/arm/clone.S
+ */
+
+#define SYS_clone 120
+#define SYS_exit 1
+#define SYS_getpid 20
+
+#define __ARM_EABI__  1
+
+#define CLONE_VM      0x00000100
+#define CLONE_THREAD  0x00010000
+
+	.text
+	.globl lx_clone
+	.type lx_clone, #function
+lx_clone:
+
+	@ insert the args onto the new stack
+	str	r3, [r1, #-4]!
+	str	r0, [r1, #-4]!
+
+	@ do the system call
+	@ get flags
+	mov	r0, r2
+#ifdef RESET_PID
+	mov	ip, r2
+#endif
+	@ new sp is already in r1
+#ifdef __ARM_EABI__
+	stmfd	sp!, {r4, r7}
+#else
+	str	r4, [sp, #-8]!
+#endif
+	ldr	r2, [sp, #8]
+	ldr	r3, [sp, #12]
+	ldr	r4, [sp, #16]
+#ifdef __ARM_EABI__
+	ldr	r7, =SYS_clone
+	swi	0x0
+#else
+	swi	SYS_clone
+#endif
+	cmp	r0, #0
+	beq	1f
+#ifdef __ARM_EABI__
+	ldmfd	sp!, {r4, r7}
+#else
+	ldr	r4, [sp], #8
+#endif
+	#blt	PLTJMP(C_SYMBOL_NAME(__syscall_error))
+	bx lr
+
+1:
+#ifdef RESET_PID
+	tst	ip, #CLONE_THREAD
+	bne	3f
+	mov	r0, #0xffff0fff
+	mov	lr, pc
+	sub	pc, r0, #31
+	mov	r1, r0
+	tst	ip, #CLONE_VM
+	movne	r0, #-1
+#ifdef __ARM_EABI__
+	ldr	r7, =SYS_getpid
+	swieq	0x0
+#else
+	swieq	SYS_getpid
+#endif
+	str	r0, [r1, #PID_OFFSET]
+	str	r0, [r1, #TID_OFFSET]
+3:
+#endif
+	@ pick the function arg and call address off the stack and execute
+	ldr	r0, [sp, #4]
+#if defined(__ARM_ARCH_4T__) && defined(__THUMB_INTERWORK__)
+	ldr 	ip, [sp], #8
+	mov	lr, pc
+	bx      ip
+#else
+	mov	lr, pc
+	ldr 	pc, [sp], #8
+#endif
+
+	@ and we are done, passing the return value through r0
+	ldr	r7, =SYS_exit
+	swi	0x0
+
+/* tell the linker that this code does not need an executable stack */
+.section .note.GNU-stack, "", %progbits

base-linux/src/platform/arm/lx_syscall.S

@@ -0,0 +1,29 @@
+/*
+ * \brief  Linux syscall() binding
+ * \author Christian Prochaska
+ * \date   2012-05-05
+ *
+ * based on eglibc-2.11.3/ports/sysdeps/unix/sysv/linux/arm/syscall.S
+ *
+ * error case:
+ *   glibc's syscall() function returns -1 and sets errno
+ *   lx_syscall() returns -errno
+ */
+
+	.text
+	.globl lx_syscall
+	.type lx_syscall, #function
+lx_syscall:
+	mov	ip, sp
+	stmfd	sp!, {r4, r5, r6, r7}
+	mov	r7, r0
+	mov	r0, r1
+	mov	r1, r2
+	mov	r2, r3
+	ldmfd	ip, {r3, r4, r5, r6}
+	swi	0x0
+	ldmfd	sp!, {r4, r5, r6, r7}
+	bx	lr
+
+/* tell the linker that this code does not need an executable stack */
+.section .note.GNU-stack, "", %progbits

base/src/platform/arm/crt0.s

@@ -17,15 +17,25 @@
 	.globl _start
 _start:
 
-	ldr  sp, .initial_sp
+	ldr r4, .initial_sp
+	str sp, [r4]
+
+	ldr  sp, .stack_high
 	b    _main
 
-.initial_sp: .word _stack_high
+.initial_sp: .word __initial_sp
+.stack_high: .word _stack_high
 
+/*--------------------------------------------------*/
+        .data
 	.globl	__dso_handle
 __dso_handle:
 	.long	0
 
+	.globl  __initial_sp
+__initial_sp:
+	.long   0
+
 /*--- .bss (non-initialized data) ------------------*/
 .section ".bss"
 

libports/lib/mk/arm/libc-gen.mk

@@ -12,7 +12,4 @@ SRC_C  += $(filter-out $(FILTER_OUT_C),$(notdir $(wildcard $(LIBC_GEN_ARM_DIR)/*
 # fix missing include prefix for 'ucontext.h', should be 'sys/ucontext.h'
 CC_OPT_makecontext = -I$(REP_DIR)/include/libc/sys
 
-# needed to compile setjmp.S
-CC_OPT += -DSOFTFLOAT
-
 vpath % $(LIBC_GEN_ARM_DIR)

libports/lib/mk/arm/libc-setjmp.mk

@@ -7,6 +7,13 @@ SRC_S   = _setjmp.S setjmp.S
 #
 CC_OPT += -D_STANDALONE
 
+#
+# Needed to compile on hard-float Linux
+# FIXME: Floating point registers don't get saved/restored
+#        when using this definition!
+#
+CC_OPT += -D__SOFTFP__
+
 include $(REP_DIR)/lib/mk/libc-common.inc
 
 vpath %.S $(LIBC_GEN_ARM_DIR)

os/lib/mk/arm/ldso_crt0_lx.mk

@@ -0,0 +1,3 @@
+SRC_S = crt0.s
+
+vpath crt0.s $(REP_DIR)/src/lib/ldso/arm/linux

os/src/lib/ldso/arm/crt0.s

@@ -20,10 +20,14 @@ _start_ldso:
 	ldr r2, .initial_utcb
 	str r0, [r2]
 
-	ldr  sp, .initial_sp
+	ldr r2, .initial_sp
+	str sp, [r2]
+
+	ldr  sp, .stack_high
 	bl init_rtld
 	b    _main
 
-	.initial_sp:   .word _stack_high
+	.initial_sp:   .word __initial_sp
+	.stack_high:   .word _stack_high
 	.initial_utcb: .word _main_utcb
 

os/src/lib/ldso/arm/linux/crt0.s

@@ -0,0 +1,58 @@
+/*
+ * \brief   Startup code for ld.lib.so (linux_arm)
+ * \author  Christian Prochaska
+ * \date    2012-07-06
+ */
+
+/*
+ * Copyright (C) 2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/*--- .text (program code) -------------------------*/
+.section ".text.crt0"
+
+	.globl _start_ldso
+_start_ldso:
+
+	ldr	sl, .L_GOT
+.L_GOT_OFF:
+	add	sl, pc, sl
+
+	ldr r1, .initial_sp
+	ldr r1, [sl, r1]
+	str sp, [r1]
+
+	/*
+	 * environ = &argv[argc + 1]
+	 * in Genode argc is always 1
+	 */
+	add sp, sp,#12
+	ldr r1, .lx_environ
+	ldr r1, [sl, r1]
+	str sp, [r1]
+
+	/* XXX Switch to our own stack.  */
+	ldr r1, .stack_high
+	ldr sp, [sl, r1]
+
+	/* relocate ldso */
+	mov r1, #0
+	bl init_rtld
+
+	/*
+	 * Clear the frame pointer and the link register so that stack
+	 * backtraces will work.
+	 */
+	mov fp, #0
+	mov lr, #0
+
+	/* Jump into init C code */
+	b _main
+
+	.L_GOT:		.word _GLOBAL_OFFSET_TABLE_ - (.L_GOT_OFF + 8)
+	.initial_sp:    .word __initial_sp(GOT)
+	.lx_environ:	.word lx_environ(GOT)
+	.stack_high:	.word _stack_high(GOT)

os/src/lib/ldso/include/arm/call_main.h

@@ -18,7 +18,15 @@
 	 */
 void call_main(void (*func)(void))
 {
-	func();
+        extern long __initial_sp;
+
+        asm volatile ("mov %%sp, %0;"
+                      "bx %1;"
+                      :
+                      : "r" (__initial_sp),
+                        "r" (func)
+                      : "memory"
+                     );
 }
 
 #endif /* _ARM__CALL_MAIN_H_ */

tool/builddir/etc/build.conf.linux_arm

@@ -0,0 +1 @@
+REPOSITORIES  = $(GENODE_DIR)/base-linux

tool/create_builddir

@@ -20,6 +20,7 @@ usage:
 	@echo
 	@echo "  <platform>   can be:"
 	@echo "                  'linux_x86'"
+	@echo "                  'linux_arm'"
 	@echo "                  'fiasco_x86'"
 	@echo "                  'pistachio_x86'"
 	@echo "                  'okl4_x86'"