CHROMIUM: arch/arm: add asm/syscall.h

(I will post this upstream after the 3.5 merge window)

Provide an ARM implementation for asm-generic/syscall.h.
This is a pre-requisite for CONFIG_HAVE_ARCH_TRACEHOOK and
CONFIG_HAVE_ARCH_SECCOMP_FILTER.  The latter is the forcing
function for this patch.

Change-Id: Idc5fa7b72691ec9d75418849733633df33482e53
Signed-off-by: Will Drewry <wad@chromium.org>

BUG=chromium-os:27878
TEST=compiles for arm. Need to test on a live machine.

Change-Id: I7b911b51085424aedd2beaf40683c3348b6cede1
Reviewed-on: https://gerrit.chromium.org/gerrit/21375


Reviewed-by: Will Drewry <wad@chromium.org>
Tested-by: Will Drewry <wad@chromium.org>
Signed-off-by: Sasha Levitskiy <sanek@google.com>

arch/arm/include/asm/syscall.h

+/*
+ * Access to user system call parameters and results
+ *
+ * Copyright (C) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU General Public License v.2.
+ *
+ * See asm-generic/syscall.h for descriptions of what we must do here.
+ */
+#ifndef _ASM_ARM_SYSCALL_H
+#define _ASM_ARM_SYSCALL_H
+
+#include <linux/audit.h> /* for AUDIT_ARCH_* */
+#include <linux/elf.h> /* for ELF_EM */
+#include <linux/sched.h>
+#include <linux/thread_info.h> /* for task_thread_info */
+#include <linux/err.h>
+
+static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
+{
+	return task_thread_info(task)->syscall;
+}
+
+static inline void syscall_rollback(struct task_struct *task,
+				    struct pt_regs *regs)
+{
+	regs->ARM_r0 = regs->ARM_ORIG_r0;
+}
+
+static inline long syscall_get_error(struct task_struct *task,
+				     struct pt_regs *regs)
+{
+	unsigned long error = regs->ARM_r0;
+	return IS_ERR_VALUE(error) ? error : 0;
+}
+
+static inline long syscall_get_return_value(struct task_struct *task,
+					    struct pt_regs *regs)
+{
+	return regs->ARM_r0;
+}
+
+static inline void syscall_set_return_value(struct task_struct *task,
+					    struct pt_regs *regs,
+					    int error, long val)
+{
+	regs->ARM_r0 = (long) error ?: val;
+}
+
+static inline void syscall_get_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 unsigned long *args)
+{
+	BUG_ON(i + n > 6);
+	memcpy(args, &regs->ARM_r1 + i, n * sizeof(args[0]));
+}
+
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 const unsigned long *args)
+{
+	BUG_ON(i + n > 6);
+	memcpy(&regs->ARM_r1 + i, args, n * sizeof(args[0]));
+}
+
+static inline int syscall_get_arch(struct task_struct *task,
+				    struct pt_regs *regs)
+{
+	/* ARM tasks don't change audit architectures on the fly. */
+#ifdef __ARMEB__
+	return AUDIT_ARCH_ARMEB;
+#else
+	return AUDIT_ARCH_ARM;
+#endif
+}
+#endif	/* _ASM_ARM_SYSCALL_H */