[PATCH 16/17] arm: asm/syscall.h (unfinished)

[Roland McGrath <roland@redhat.com>]

This provides the user_stack_pointer() macro in asm/ptrace.h,
which some new arch-independent code wants to be able to use.

It also adds the asm/syscall.h header to let arch-independent
code interpret the registers as system call arguments or return.

The syscall_get_nr() function here is not really right.  I don't
know enough about ARM to finish it correctly.  It needs to figure
out if the blocked user task is really in the kernel for a system
call and return -1 if not.  I also did not try to handle all the
different ABI variants, which I don't really understand.

Until this is fixed, /proc/pid/syscall can show bogus results
for a process that is blocked inside a fault or something else
that's not a system call.  (It's probably all wrong for !AEABI too.)

Signed-off-by: Roland McGrath <roland@redhat.com>
---
 arch/arm/include/asm/ptrace.h  |    4 +-
 arch/arm/include/asm/syscall.h |   65 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 arch/arm/include/asm/syscall.h

diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index 236a06b..34075dc 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -140,7 +140,8 @@ static inline int valid_user_regs(struct pt_regs *regs)
 	return 0;
 }
 
-#define instruction_pointer(regs)	(regs)->ARM_pc
+#define instruction_pointer(regs)	((regs)->ARM_pc)
+#define user_stack_pointer(regs)	((regs)->ARM_sp)
 
 #ifdef CONFIG_SMP
 extern unsigned long profile_pc(struct pt_regs *regs);
@@ -156,4 +157,3 @@ extern unsigned long profile_pc(struct pt_regs *regs);
 #endif /* __ASSEMBLY__ */
 
 #endif
-
diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
new file mode 100644
index 0000000..56aefe6
--- /dev/null
+++ b/arch/arm/include/asm/syscall.h
@@ -0,0 +1,65 @@
+/*
+ * Access to user system call parameters and results
+ *
+ * See asm-generic/syscall.h for descriptions of what we must do here.
+ */
+
+#ifndef _ASM_SYSCALL_H
+#define _ASM_SYSCALL_H	1
+
+#include <linux/sched.h>
+#include <linux/err.h>
+
+static inline long syscall_get_nr(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	/* XXX how to figure out if blocked in a syscall or not?? */
+
+	return regs->ARM_r7;	/* XXX apparently */
+	return task_thread_info(task)->syscall; /* XXX if changed via ptrace */
+}
+
+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)
+{
+	return IS_ERR_VALUE(regs->ARM_r0) ? regs->ARM_r0 : 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->uregs[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->uregs[i], args, n * sizeof(args[0]));
+}
+
+#endif	/* _ASM_SYSCALL_H */