[PATCH] ARM: Added user space support for c/r on ARM

Christoffer Dall christofferdall at christofferdall.dk
Wed Apr 28 00:29:12 PDT 2010


Hi Matt.

Thanks for the feedback. I have changed the path according to your comments
and am attaching it below.

 - Let me know if I need to adjust my patch before inclusion with respect to
   the s/clone_with_pids// later.

 - Much better with the 'local SYS_NR_DEF_REGEX' in get_unistd_regex().
   Thanks.

 - I pondered about inserting arch-specific code when printing the header
   content, and thought about a file function like add_arch_syscall_base()
   but it seems rhather synthetic as I think ARM is the only possible
   architecture, which would use it. Instead, I added whitespace around the
   line as you suggest.

 - I agree regarding the make variables - it was simply a glitch. I
   adjusted the assignment in both Makefile and test/Makefile.


Thanks,
Christoffer

diff --git a/Makefile b/Makefile
index 6c9ff93..37ed40a 100644
--- a/Makefile
+++ b/Makefile
@@ -18,6 +18,13 @@ CR_OBJS = checkpoint.o checkpoint-main.o restart.o restart-main.o
 # detect architecture (for eclone)
 SUBARCH ?= $(patsubst i%86,x86_32,$(shell uname -m))
 
+# handle cross-compilation
+AR  := ${CROSS_COMPILE}ar
+AS  := ${CROSS_COMPILE}as
+CC  := ${CROSS_COMPILE}gcc
+CPP := ${CROSS_COMPILE}cpp
+LD  := ${CROSS_COMPILE}ld
+
 # compile with debug ?
 DEBUG = -DCHECKPOINT_DEBUG
 
@@ -77,6 +84,11 @@ ASFLAGS += -m64
 $(LIB_ECLONE): clone_$(SUBARCH)_.o
 endif
 
+# also on ARM, need also assembly file
+ifeq ($(SUBARCH),arm)
+$(LIB_ECLONE): eclone_$(SUBARCH)_.o
+endif
+
 # ckptinfo dependencies
 ckptinfo: ckptinfo_types.o
 
diff --git a/clone.h b/clone.h
index 3569a45..b6b18ce 100644
--- a/clone.h
+++ b/clone.h
@@ -25,6 +25,14 @@
 #    define __NR_unshare 303
 #elif __powerpc__
 #    define __NR_unshare 282
+#elif __arm__
+#    define __NR_OABI_SYSCALL_BASE 0x900000
+#    if defined(__thumb__) || defined(__ARM_EABI__)
+#        define __NR_SYSCALL_BASE 0
+#    else
+#        define __NR_SYSCALL_BASE __NR_OABI_SYSCALL_BASE
+#    endif
+#    define __NR_unshare (__NR_SYSCALL_BASE+337)
 #else
 #    error "Architecture not supported"
 #endif
diff --git a/clone_arm.c b/clone_arm.c
new file mode 100644
index 0000000..b62b4ad
--- /dev/null
+++ b/clone_arm.c
@@ -0,0 +1,79 @@
+/*
+ *  clone_arm.c: support for eclone() on ARM
+ *
+ *  Author:	Christoffer Dall <christofferdall at christofferdall.dk>
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of the Linux
+ *  distribution for more details.
+ */
+
+#define _GNU_SOURCE
+
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/syscall.h>
+#include <asm/unistd.h>
+
+/*
+ * libc doesn't support eclone() yet...
+ * below is arch-dependent code to use the syscall
+ */
+#include <linux/checkpoint.h>
+
+#include "eclone.h"
+
+extern int __eclone(int clone_flags_low,
+		    struct clone_args *clone_args,
+		    unsigned int args_size,
+		    pid_t *pids);
+
+static unsigned long get_stack_pointer(unsigned long base, unsigned long size)
+{
+	size_t page_size = sysconf(_SC_PAGESIZE);
+	return (base + size - page_size) - 1;
+}
+
+int eclone(int (*fn)(void *), void *fn_arg, int clone_flags_low,
+	   struct clone_args *clone_args, pid_t *pids)
+{
+	struct clone_args my_args;
+	long newpid;
+	void **sp = NULL;
+
+	if (!fn) {
+		fprintf(stderr, "Please provide a valid function pointer "
+				"for the child process.\n");
+		return -1;
+	}
+
+	if (clone_args->child_stack) {
+		sp = (void **)get_stack_pointer(clone_args->child_stack,
+						clone_args->child_stack_size);
+		*--sp = fn_arg;
+		*--sp = fn;
+	} else {
+		fprintf(stderr, "The ARM architecture requires a valid child "
+				"stack. clon_args->child_stack was 0.\n");
+		return -1;
+	}
+
+
+	my_args = *clone_args;
+	my_args.child_stack = (unsigned long long)sp;
+	my_args.child_stack_size = 0;
+
+	newpid = __eclone(clone_flags_low,
+			  &my_args,
+			  sizeof(my_args),
+			  pids);
+
+	if (newpid < 0) {
+		errno = -newpid;
+		newpid = -1;
+	}
+
+	return newpid;
+}
diff --git a/eclone_arm_.S b/eclone_arm_.S
new file mode 100644
index 0000000..0f71d0f
--- /dev/null
+++ b/eclone_arm_.S
@@ -0,0 +1,86 @@
+/*
+ *  eclone_arm_.S: ARM support for eclone()
+ *
+ *  Author:	Christoffer Dall <christofferdall at christofferdall.dk>
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of the Linux
+ *  distribution for more details.
+ */
+
+#define _ERRNO_H	1
+#include <bits/errno.h>
+#include <asm/unistd.h>
+
+
+#define CLONE_VM      0x00000100
+#define CLONE_THREAD  0x00010000
+
+#ifndef __NR_eclone
+#define __NR_eclone 366
+#endif
+
+/*
+ * Implements the following system call wrapper:
+ *
+ *	extern int __eclone(int clone_flags_low,
+ *			    struct clone_args *clone_args,
+ *			    pid_t *pids);
+ *
+ * The system call wrapper and the system call themselves have slightly
+ * different layouts and the following transformation takes place in
+ * the code below:
+ *
+ */
+
+        .text
+	.align 4
+	.globl __eclone
+	.type __eclone,%function
+__eclone:
+	@ save flags
+	mov	ip, r0
+
+	@ do the system call
+#ifdef __ARM_EABI__
+	str	r7, [sp, #-4]!
+	ldr	r7, =__NR_eclone
+	swi	0x0
+#else
+	swi	__NR_eclone
+#endif
+	cmp	r0, #0
+	beq	1f
+#ifdef __ARM_EABI__
+	ldr	r7, [sp], #4
+#endif
+	@ return to caller
+	bx	lr
+
+1:
+	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, =__NR_getpid
+	swieq	0x0
+#else
+	swieq	__NR_getpid
+#endif
+	str	r0, [r1, #-1108]
+	str	r0, [r1, #-1112]
+3:
+	@ pick the function arg and call address off the stack and execute
+	ldr	r0, [sp, #4]
+	mov	lr, pc
+	ldr 	pc, [sp], #8
+
+	@ and we are done, passing the return value through r0
+	@b       PLTJMP(HIDDEN_JUMPTARGET(_exit))
+	b	_exit
+
diff --git a/include/asm-arm/checkpoint_hdr.h b/include/asm-arm/checkpoint_hdr.h
new file mode 100644
index 0000000..9295f85
--- /dev/null
+++ b/include/asm-arm/checkpoint_hdr.h
@@ -0,0 +1,55 @@
+/*
+ * Generated by extract-headers.sh.
+ */
+#ifndef __ASM_ARM_CHECKPOINT_HDR_H_
+#define __ASM_ARM_CHECKPOINT_HDR_H_
+
+/*
+ *  Checkpoint/restart - architecture specific headers ARM
+ *
+ *  Copyright (C) 2008-2010 Oren Laadan
+ *  Copyright (C)      2010 Christoffer Dall
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of the Linux
+ *  distribution for more details.
+ */
+
+#include <linux/types.h>
+
+/* ARM structure seen from kernel/userspace */
+
+#define CKPT_ARCH_ID CKPT_ARCH_ARM
+
+/* arch dependent constants */
+#define CKPT_ARCH_NSIG 64
+#define CKPT_TTY_NCC 8
+
+struct ckpt_hdr_header_arch {
+	struct ckpt_hdr h;
+	__u32	cpu_architecture;
+	__u8	mmu;		/* Checkpointed on mmu system */
+	__u8	aeabi;		/* Checkpointed on AEABI kernel */
+	__u8	oabi_compat;	/* Checkpointed on OABI compat. system */
+} __attribute__((aligned(8)));
+
+struct ckpt_hdr_thread {
+	struct ckpt_hdr h;
+	__u32		syscall;
+	__u32		tp_value;
+	__u32		thumbee_state;
+} __attribute__((aligned(8)));
+
+struct ckpt_hdr_cpu {
+	struct ckpt_hdr h;
+	__u32		uregs[18];
+} __attribute__((aligned(8)));
+
+struct ckpt_hdr_mm_context {
+	struct ckpt_hdr h;
+	__u32		end_brk;
+} __attribute__((aligned(8)));
+
+
+
+#endif /* __ASM_ARM_CHECKPOINT_HDR_H_ */
diff --git a/include/asm/checkpoint_hdr.h b/include/asm/checkpoint_hdr.h
index 859f58e..7f18e0e 100644
--- a/include/asm/checkpoint_hdr.h
+++ b/include/asm/checkpoint_hdr.h
@@ -3,7 +3,9 @@
  */
 #ifndef __ASM_CHECKPOINT_HDR_H_
 #define __ASM_CHECKPOINT_HDR_H_
-#if __powerpc__
+#if __arm__
+#include <asm-arm/checkpoint_hdr.h>
+#elif __powerpc__
 #include <asm-powerpc/checkpoint_hdr.h>
 #elif __s390x__
 #include <asm-s390/checkpoint_hdr.h>
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index f6a6448..359023f 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -31,7 +31,25 @@
 #define CHECKPOINT_FD_NONE -1
 
 
-#if __powerpc__
+#if __arm__
+
+#	define __NR_OABI_SYSCALL_BASE 0x900000
+#	if defined(__thumb__) || defined(__ARM_EABI__)
+#		define __NR_SYSCALL_BASE	0
+#	else
+#		define __NR_SYSCALL_BASE	__NR_OABI_SYSCALL_BASE
+#	endif
+
+
+#	ifndef __NR_checkpoint
+#		define __NR_checkpoint (__NR_SYSCALL_BASE+367)
+#	endif
+
+#	ifndef __NR_restart
+#		define __NR_restart (__NR_SYSCALL_BASE+368)
+#	endif
+
+#elif __powerpc__
 
 #	ifndef __NR_checkpoint
 #		define __NR_checkpoint 324
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 65d5256..214cd11 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -202,6 +202,8 @@ enum {
 #define CKPT_ARCH_PPC32 CKPT_ARCH_PPC32
 	CKPT_ARCH_PPC64,
 #define CKPT_ARCH_PPC64 CKPT_ARCH_PPC64
+	CKPT_ARCH_ARM,
+#define CKPT_ARCH_ARM CKPT_ARCH_ARM
 };
 
 /* shared objrects (objref) */
diff --git a/scripts/extract-headers.sh b/scripts/extract-headers.sh
index 8c8ae69..19f63b4 100755
--- a/scripts/extract-headers.sh
+++ b/scripts/extract-headers.sh
@@ -144,7 +144,27 @@ echo '#endif /* _CHECKPOINT_CKPT_HDR_H_ */' >> "${OUTPUT_INCLUDES}/linux/checkpo
 # We use ARCH_COND to break up architecture-specific sections of the header.
 #
 ARCH_COND='#if'
-REGEX='[[:space:]]*#[[:space:]]*define[[:space:]]*__NR_(checkpoint|restart|clone_with_pids)[[:space:]]+[0-9]+'
+ARM_SYSCALL_BASE="#	define __NR_OABI_SYSCALL_BASE 0x900000\n\
+#	if defined(__thumb__) || defined(__ARM_EABI__)\n\
+#		define __NR_SYSCALL_BASE	0\n\
+#	else\n\
+#		define __NR_SYSCALL_BASE	__NR_OABI_SYSCALL_BASE\n\
+#	endif\n"
+
+# Get the regular expression for the current architecture
+function get_unistd_regex()
+{
+	local SYS_NR_DEF_REGEX='[[:space:]]*#[[:space:]]*define[[:space:]]*__NR_(checkpoint|restart|clone_with_pids)[[:space:]]+'
+
+	case "$1" in
+	arm)	echo -n "${SYS_NR_DEF_REGEX}"
+		echo -n '\(__NR_SYSCALL_BASE\+[[:space:]]*[0-9]*\)'
+		;;
+	*)	echo -n "${SYS_NR_DEF_REGEX}"'[0-9]+'
+		;;
+	esac
+	return 0
+}
 
 cat - <<-EOFOE
 /*
@@ -160,11 +180,15 @@ do_cpp "${KERNELSRC}/include/linux/checkpoint.h" "_LINUX_CHECKPOINT_H_"
 find "${KERNELSRC}/arch" -name 'unistd*.h' -print | sort | \
 while read UNISTDH ; do
 	[ -n "${UNISTDH}" ] || continue
-	grep -q -E "${REGEX}" "${UNISTDH}" || continue
 	KARCH=$(echo "${UNISTDH}" | sed -e 's|.*/arch/\([^/]\+\)/.*|\1|')
+	REGEX="$(get_unistd_regex "${KARCH}")"
+	grep -q -E "${REGEX}" "${UNISTDH}" || continue
 	WORDBITS=$(basename "${UNISTDH}" | sed -e 's/unistd_*\([[:digit:]]\+\)\.h/\1/')
 	CPPARCH="$(karch_to_cpparch "${KARCH}" "${WORDBITS}")"
 	echo -e "${ARCH_COND} __${CPPARCH}__\\n"
+
+	[ "${KARCH}" == "arm" ] && echo -e "${ARM_SYSCALL_BASE}\n"
+
 	grep -E "${REGEX}" "${UNISTDH}" | \
 	sed -e 's/^[ \t]*#[ \t]*define[ \t]*__NR_\([^ \t]\+\)[ \t]\+\([^ \t]\+\).*$/#\tifndef __NR_\1\n#\t\tdefine __NR_\1 \2\n#\tendif\n/'
 	ARCH_COND='#elif'
diff --git a/test/Makefile b/test/Makefile
index cad40e0..516eee8 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,3 +1,9 @@
+# handle cross-compilation
+AR = ${CROSS_COMPILE}ar
+AS = ${CROSS_COMPILE}as
+CC = ${CROSS_COMPILE}gcc
+CPP = ${CROSS_COMPILE}cpp
+LD = ${CROSS_COMPILE}ld
 
 # extra warnings and fun
 WARNS := -Wall -Wstrict-prototypes -Wno-trigraphs
-- 
1.5.6.5



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