diff options
Diffstat (limited to 'arch/microblaze/include/asm/entry.h')
| -rw-r--r-- | arch/microblaze/include/asm/entry.h | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/arch/microblaze/include/asm/entry.h b/arch/microblaze/include/asm/entry.h index e4c3aef884df..61abbd232640 100644 --- a/arch/microblaze/include/asm/entry.h +++ b/arch/microblaze/include/asm/entry.h @@ -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 @@ -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 */ |