root / prex-0.9.0 / bsp / hal / arm / arch / context.c @ 03e9c04a
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/*-
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* Copyright (c) 2005-2009, Kohsuke Ohtani
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* context.c - context management routines
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*/
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/*
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* The context consists of kernel/user mode registers, and
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* kernel stack. The user mode registers are always saved to the
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* kernel stack when processor enters kernel mode by H/W or S/W events.
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*
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* The user mode registers are located in the interrupt/trap frame
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* at the top of the kernel stack. Before the control returns to user
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* mode next time, these register value will be restored automatically.
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*
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* All thread owns its context to keep its execution state. The
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* scheduler will switch the context to change an active thread.
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*/
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#include <kernel.h> |
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#include <kmem.h> |
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#include <cpu.h> |
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#include <context.h> |
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#include <locore.h> |
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#include <trap.h> |
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/*
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* Set data to the specific register stored in context.
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*
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* Note: When user mode program counter is set, all register
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* values except stack pointer are reset to default value.
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*/
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void
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context_set(context_t ctx, int type, register_t val)
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{ |
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struct kern_regs *k;
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struct cpu_regs *u;
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k = &ctx->kregs; |
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switch (type) {
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case CTX_KSTACK:
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/* Set kernel mode stack pointer */
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ctx->uregs = (struct cpu_regs *)
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((vaddr_t)val - sizeof(struct cpu_regs)); |
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k->sp = (uint32_t)ctx->uregs; |
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/* Reset minimum user mode registers */
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u = ctx->uregs; |
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u->r0 = 0;
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u->r1 = 0x11111111;
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u->r2 = 0x22222222;
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u->r3 = 0x33333333;
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u->svc_sp = (uint32_t)val; |
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u->cpsr = PSR_APP_MODE; /* FIQ/IRQ is enabled */
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break;
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case CTX_KENTRY:
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/* Kernel mode program counter */
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k->lr = (uint32_t)&kernel_thread_entry; |
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k->r4 = (uint32_t)val; |
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break;
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case CTX_KARG:
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/* Kernel mode argument */
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k->r5 = (uint32_t)val; |
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break;
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case CTX_USTACK:
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/* User mode stack pointer */
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u = ctx->uregs; |
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u->sp = (uint32_t)val; |
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break;
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case CTX_UENTRY:
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/* User mode program counter */
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u = ctx->uregs; |
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u->cpsr = PSR_APP_MODE; /* FIQ/IRQ is enabled */
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u->pc = (uint32_t)val; |
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u->lr = 0x12345678;
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break;
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case CTX_UARG:
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/* User mode argument */
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u = ctx->uregs; |
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u->r0 = (uint32_t)val; /* Argument 1 */
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break;
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default:
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/* invalid */
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break;
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} |
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} |
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/*
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* Switch to new context
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*
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* Kernel mode registers and kernel stack pointer are switched to
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* the next context.
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*
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* It is assumed all interrupts are disabled by caller.
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*
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* TODO: FPU context is not switched as of now.
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*/
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void
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context_switch(context_t prev, context_t next) |
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{ |
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cpu_switch(&prev->kregs, &next->kregs); |
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} |
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/*
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* Save user mode context to handle exceptions.
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*
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* Copy current user mode registers in the kernel stack to the user
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* mode stack. The user stack pointer is adjusted for this area.
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* So that the exception handler can get the register state of
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* the target thread.
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*
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* It builds arguments for the exception handler in the following
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* format.
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*
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* void exception_handler(int exc, void *regs);
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*/
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void
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context_save(context_t ctx) |
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{ |
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struct cpu_regs *cur, *sav;
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/* Copy current register context into user mode stack */
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cur = ctx->uregs; |
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sav = (struct cpu_regs *)(cur->sp - sizeof(struct cpu_regs)); |
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copyout(cur, sav, sizeof(*sav));
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ctx->saved_regs = sav; |
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/* Adjust stack pointer */
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cur->sp = (uint32_t)sav - sizeof(uint32_t);
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} |
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/*
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* Restore register context to return from the exception handler.
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*/
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void
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context_restore(context_t ctx) |
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{ |
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struct cpu_regs *cur;
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/* Restore user mode context */
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cur = ctx->uregs; |
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copyin(ctx->saved_regs, cur, sizeof(*cur));
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/* Correct some registers for fail safe */
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cur->cpsr = (cur->cpsr & ~PSR_MODE) | PSR_APP_MODE; |
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} |
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void
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context_dump(context_t ctx) |
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{ |
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#ifdef DEBUG
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trap_dump(ctx->uregs); |
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#endif
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} |