arch/microblaze/include/asm/entry.h

   1 /*
   2  * Definitions used by low-level trap handlers
   3  *
   4  * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
   5  * Copyright (C) 2007-2009 PetaLogix
   6  * Copyright (C) 2007 John Williams <john.williams@petalogix.com>
   7  *
   8  * This file is subject to the terms and conditions of the GNU General
   9  * Public License. See the file COPYING in the main directory of this
  10  * archive for more details.
  11  */
  12
  13 #ifndef _ASM_MICROBLAZE_ENTRY_H
  14 #define _ASM_MICROBLAZE_ENTRY_H
  15
  16 #include <asm/percpu.h>
  17 #include <asm/ptrace.h>
  18
  19 /*
  20  * These are per-cpu variables required in entry.S, among other
  21  * places
  22  */
  23
  24 #define PER_CPU(var) per_cpu__##var
  25
  26 # ifndef __ASSEMBLY__
  27 DECLARE_PER_CPU(unsigned int, KSP); /* Saved kernel stack pointer */
  28 DECLARE_PER_CPU(unsigned int, KM); /* Kernel/user mode */
  29 DECLARE_PER_CPU(unsigned int, ENTRY_SP); /* Saved SP on kernel entry */
  30 DECLARE_PER_CPU(unsigned int, R11_SAVE); /* Temp variable for entry */
  31 DECLARE_PER_CPU(unsigned int, CURRENT_SAVE); /* Saved current pointer */
  32 # endif /* __ASSEMBLY__ */
  33
  34 #ifndef CONFIG_MMU
  35
  36 /* noMMU hasn't any space for args */
  37 # define STATE_SAVE_ARG_SPACE   (0)
  38
  39 #else /* CONFIG_MMU */
  40
  41 /* If true, system calls save and restore all registers (except result
  42  * registers, of course).  If false, then `call clobbered' registers
  43  * will not be preserved, on the theory that system calls are basically
  44  * function calls anyway, and the caller should be able to deal with it.
  45  * This is a security risk, of course, as `internal' values may leak out
  46  * after a system call, but that certainly doesn't matter very much for
  47  * a processor with no MMU protection!  For a protected-mode kernel, it
  48  * would be faster to just zero those registers before returning.
  49  *
  50  * I can not rely on the glibc implementation. If you turn it off make
  51  * sure that r11/r12 is saved in user-space. --KAA
  52  *
  53  * These are special variables using by the kernel trap/interrupt code
  54  * to save registers in, at a time when there are no spare registers we
  55  * can use to do so, and we can't depend on the value of the stack
  56  * pointer.  This means that they must be within a signed 16-bit
  57  * displacement of 0x00000000.
  58  */
  59
  60 /* A `state save frame' is a struct pt_regs preceded by some extra space
  61  * suitable for a function call stack frame. */
  62
  63 /* Amount of room on the stack reserved for arguments and to satisfy the
  64  * C calling conventions, in addition to the space used by the struct
  65  * pt_regs that actually holds saved values. */
  66 #define STATE_SAVE_ARG_SPACE    (6*4) /* Up to six arguments */
  67
  68 #endif /* CONFIG_MMU */
  69
  70 #endif /* _ASM_MICROBLAZE_ENTRY_H */