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microblaze_mmu_v2: entry.S, entry.h
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Signed-off-by: Michal Simek <monstr@monstr.eu>
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Michal Simek committed May 26, 2009
1 parent 23cfc36 commit ca54502
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37 changes: 35 additions & 2 deletions arch/microblaze/include/asm/entry.h
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
/*
* Definitions used by low-level trap handlers
*
* Copyright (C) 2008 Michal Simek
* Copyright (C) 2007 - 2008 PetaLogix
* Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
* Copyright (C) 2007-2009 PetaLogix
* Copyright (C) 2007 John Williams <john.williams@petalogix.com>
*
* This file is subject to the terms and conditions of the GNU General
Expand Down Expand Up @@ -31,7 +31,40 @@ DECLARE_PER_CPU(unsigned int, R11_SAVE); /* Temp variable for entry */
DECLARE_PER_CPU(unsigned int, CURRENT_SAVE); /* Saved current pointer */
# endif /* __ASSEMBLY__ */

#ifndef CONFIG_MMU

/* noMMU hasn't any space for args */
# define STATE_SAVE_ARG_SPACE (0)

#else /* CONFIG_MMU */

/* If true, system calls save and restore all registers (except result
* registers, of course). If false, then `call clobbered' registers
* will not be preserved, on the theory that system calls are basically
* function calls anyway, and the caller should be able to deal with it.
* This is a security risk, of course, as `internal' values may leak out
* after a system call, but that certainly doesn't matter very much for
* a processor with no MMU protection! For a protected-mode kernel, it
* would be faster to just zero those registers before returning.
*
* I can not rely on the glibc implementation. If you turn it off make
* sure that r11/r12 is saved in user-space. --KAA
*
* These are special variables using by the kernel trap/interrupt code
* to save registers in, at a time when there are no spare registers we
* can use to do so, and we can't depend on the value of the stack
* pointer. This means that they must be within a signed 16-bit
* displacement of 0x00000000.
*/

/* A `state save frame' is a struct pt_regs preceded by some extra space
* suitable for a function call stack frame. */

/* Amount of room on the stack reserved for arguments and to satisfy the
* C calling conventions, in addition to the space used by the struct
* pt_regs that actually holds saved values. */
#define STATE_SAVE_ARG_SPACE (6*4) /* Up to six arguments */

#endif /* CONFIG_MMU */

#endif /* _ASM_MICROBLAZE_ENTRY_H */
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