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359105bdb0
(This is a VERY IMP change for low level interrupt/exception handling) ----------------------------------------------------------------------- WHAT ----------------------------------------------------------------------- * User 25 now saved in pt_regs->user_r25 (vs. tsk->thread_info.user_r25) * This allows Low level interrupt code to unconditionally save r25 (vs. the prev version which would only do it for U->K transition). Ofcourse for nested interrupts, only the pt_regs->user_r25 of bottom-most frame is useful. * simplifies the interrupt prologue/epilogue * Needed for ARCv2 ISA code and done here to keep design similar with ARCompact event handling ----------------------------------------------------------------------- WHY ------------------------------------------------------------------------- With CONFIG_ARC_CURR_IN_REG, r25 is used to cache "current" task pointer in kernel mode. So when entering kernel mode from User Mode - user r25 is specially safe-kept (it being a callee reg is NOT part of pt_regs which are saved by default on each interrupt/trap/exception) - r25 loaded with current task pointer. Further, if interrupt was taken in kernel mode, this is skipped since we know that r25 already has valid "current" pointer. With 2 level of interrupts in ARCompact ISA, detecting this is difficult but still possible, since we could be in kernel mode but r25 not already saved (in fact the stack itself might not have been switched). A. User mode B. L1 IRQ taken C. L2 IRQ taken (while on 1st line of L1 ISR) So in #C, although in kernel mode, r25 not saved (infact SP not switched at all) Given that ARcompact has manual stack switching, we could use a bit of trickey - The low level code would make sure that SP is only set to kernel mode value at the very end (after saving r25). So a non kernel mode SP, even if in kernel mode, meant r25 was NOT saved. The same paradigm won't work in ARCv2 ISA since SP is auto-switched so it's setting can't be delayed/constrained. Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
153 lines
4.8 KiB
C
153 lines
4.8 KiB
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* vineetg: March 2009
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* -Implemented task_pt_regs( )
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*
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* Amit Bhor, Sameer Dhavale, Ashwin Chaugule: Codito Technologies 2004
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*/
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#ifndef __ASM_ARC_PROCESSOR_H
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#define __ASM_ARC_PROCESSOR_H
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#ifdef __KERNEL__
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#ifndef __ASSEMBLY__
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#include <asm/arcregs.h> /* for STATUS_E1_MASK et all */
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#include <asm/ptrace.h>
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/* Arch specific stuff which needs to be saved per task.
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* However these items are not so important so as to earn a place in
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* struct thread_info
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*/
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struct thread_struct {
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unsigned long ksp; /* kernel mode stack pointer */
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unsigned long callee_reg; /* pointer to callee regs */
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unsigned long fault_address; /* dbls as brkpt holder as well */
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unsigned long cause_code; /* Exception Cause Code (ECR) */
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#ifdef CONFIG_ARC_FPU_SAVE_RESTORE
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struct arc_fpu fpu;
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#endif
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};
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#define INIT_THREAD { \
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.ksp = sizeof(init_stack) + (unsigned long) init_stack, \
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}
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/* Forward declaration, a strange C thing */
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struct task_struct;
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/*
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* Return saved PC of a blocked thread.
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*/
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unsigned long thread_saved_pc(struct task_struct *t);
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#define task_pt_regs(p) \
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((struct pt_regs *)(THREAD_SIZE + (void *)task_stack_page(p)) - 1)
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/* Free all resources held by a thread. */
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#define release_thread(thread) do { } while (0)
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/* Prepare to copy thread state - unlazy all lazy status */
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#define prepare_to_copy(tsk) do { } while (0)
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/*
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* A lot of busy-wait loops in SMP are based off of non-volatile data otherwise
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* get optimised away by gcc
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*/
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#ifdef CONFIG_SMP
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#define cpu_relax() __asm__ __volatile__ ("" : : : "memory")
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#else
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#define cpu_relax() do { } while (0)
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#endif
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#define copy_segments(tsk, mm) do { } while (0)
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#define release_segments(mm) do { } while (0)
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#define KSTK_EIP(tsk) (task_pt_regs(tsk)->ret)
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/*
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* Where abouts of Task's sp, fp, blink when it was last seen in kernel mode.
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* Look in process.c for details of kernel stack layout
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*/
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#define KSTK_ESP(tsk) (tsk->thread.ksp)
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#define KSTK_REG(tsk, off) (*((unsigned int *)(KSTK_ESP(tsk) + \
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sizeof(struct callee_regs) + off)))
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#define KSTK_BLINK(tsk) KSTK_REG(tsk, 4)
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#define KSTK_FP(tsk) KSTK_REG(tsk, 0)
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/*
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* Do necessary setup to start up a newly executed thread.
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*
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* E1,E2 so that Interrupts are enabled in user mode
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* L set, so Loop inhibited to begin with
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* lp_start and lp_end seeded with bogus non-zero values so to easily catch
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* the ARC700 sr to lp_start hardware bug
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*/
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#define start_thread(_regs, _pc, _usp) \
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do { \
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set_fs(USER_DS); /* reads from user space */ \
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(_regs)->ret = (_pc); \
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/* Interrupts enabled in User Mode */ \
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(_regs)->status32 = STATUS_U_MASK | STATUS_L_MASK \
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| STATUS_E1_MASK | STATUS_E2_MASK; \
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(_regs)->sp = (_usp); \
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/* bogus seed values for debugging */ \
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(_regs)->lp_start = 0x10; \
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(_regs)->lp_end = 0x80; \
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} while (0)
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extern unsigned int get_wchan(struct task_struct *p);
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/*
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* Default implementation of macro that returns current
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* instruction pointer ("program counter").
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* Should the PC register be read instead ? This macro does not seem to
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* be used in many places so this wont be all that bad.
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*/
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#define current_text_addr() ({ __label__ _l; _l: &&_l; })
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#endif /* !__ASSEMBLY__ */
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/* Kernels Virtual memory area.
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* Unlike other architectures(MIPS, sh, cris ) ARC 700 does not have a
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* "kernel translated" region (like KSEG2 in MIPS). So we use a upper part
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* of the translated bottom 2GB for kernel virtual memory and protect
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* these pages from user accesses by disabling Ru, Eu and Wu.
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*/
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#define VMALLOC_SIZE (0x10000000) /* 256M */
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#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
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#define VMALLOC_END (PAGE_OFFSET)
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/* Most of the architectures seem to be keeping some kind of padding between
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* userspace TASK_SIZE and PAGE_OFFSET. i.e TASK_SIZE != PAGE_OFFSET.
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*/
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#define USER_KERNEL_GUTTER 0x10000000
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/* User address space:
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* On ARC700, CPU allows the entire lower half of 32 bit address space to be
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* translated. Thus potentially 2G (0:0x7FFF_FFFF) could be User vaddr space.
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* However we steal 256M for kernel addr (0x7000_0000:0x7FFF_FFFF) and another
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* 256M (0x6000_0000:0x6FFF_FFFF) is gutter between user/kernel spaces
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* Thus total User vaddr space is (0:0x5FFF_FFFF)
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*/
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#define TASK_SIZE (PAGE_OFFSET - VMALLOC_SIZE - USER_KERNEL_GUTTER)
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#define STACK_TOP TASK_SIZE
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#define STACK_TOP_MAX STACK_TOP
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/* This decides where the kernel will search for a free chunk of vm
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* space during mmap's.
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*/
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#define TASK_UNMAPPED_BASE (TASK_SIZE / 3)
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#endif /* __KERNEL__ */
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#endif /* __ASM_ARC_PROCESSOR_H */
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