290 lines
8 KiB
ArmAsm
290 lines
8 KiB
ArmAsm
/* This file is part of the lowest layer of the MINIX kernel. (The other part
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* is "proc.c".) The lowest layer does process switching and message handling.
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*
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* Kernel is entered either because of kernel-calls, ipc-calls, interrupts or
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* exceptions. TSS is set so that the kernel stack is loaded. The user context is
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* saved to the proc table and the handler of the event is called. Once the
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* handler is done, switch_to_user() function is called to pick a new process,
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* finish what needs to be done for the next process to run, sets its context
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* and switch to userspace.
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*/
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#include "kernel/kernel.h" /* configures the kernel */
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/* sections */
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#include <machine/vm.h>
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#include "kernel/kernel.h"
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#include <minix/config.h>
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#include <minix/const.h>
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#include <minix/com.h>
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#include <machine/asm.h>
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#include <machine/interrupt.h>
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#include "archconst.h"
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#include "kernel/const.h"
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#include "kernel/proc.h"
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#include "sconst.h"
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#include <machine/multiboot.h>
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#include <machine/ipcconst.h>
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#include <machine/cpu.h>
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#include <arm/armreg.h>
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#include "bsp_intr.h"
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#include "arch_proto.h" /* K_STACK_SIZE */
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IMPORT(svc_stack)
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/*
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* Adjust lr, push pc/psr when exception triggered and switch to SVC mode
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* The 'lr_offset' argument holds the adjustment.
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*
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* When an instruction causes the ARM core to enter the exception handler
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* the value of pc is stored in the link register (lr). By default on ARM
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* the program counter is 3 instruction a head of the current instruction
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* being executed (because of the 3 stage pipeline). Depending on where in
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* the pipeline the exception happens lr will need to de adjusted to find
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* the proper return address.
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*/
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.macro switch_to_svc lr_offset
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sub lr, lr, #\lr_offset /* do the adjustment */
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srsdb sp!, #PSR_SVC32_MODE /* store the saved the return */
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/* address and program status */
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/* register onto the kernel stack */
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/* Also modify the stack pointer. */
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cps #PSR_SVC32_MODE /* do the switch to SVC. */
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.endm
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/*
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* Test if the exception/interrupt occurred in the kernel.
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* Jump to 'label' argument if it occurred in the kernel.
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*
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* NOTE: switch_to_svc must be called first */
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.macro test_int_in_kernel, label
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push {r3}
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ldr r3, [sp, #8] /* get spsr. */
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orr r3, r3, #(PSR_F | PSR_I) /* mask interrupts on return. */
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str r3, [sp, #8] /* store spsr. */
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and r3, r3, #PSR_MODE /* mask the ARM mode. */
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cmp r3, #PSR_USR32_MODE /* compare it to user mode. */
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pop {r3}
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bne \label /* In-kernel handling. */
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.endm
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/* Save the register context to the proc structure */
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.macro save_process_ctx
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add sp, sp, #8 /* We expect srsdb pushed cpsr and lr on */
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/* the stack. */
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ldr lr, [sp] /* lr = proc_ptr. */
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stm lr, {r0-r14}^ /* store the user mode registers */
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/* proc_ptr->p_reg.r0-r14 = r0-r14. */
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ldr r12, [sp, #-8] /* r12 = pc stored on the stack. */
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str r12, [lr, #PCREG] /* proc_ptr->p_reg.pc = r12. */
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ldr r12, [sp, #-4] /* r12 = cpsr stored on the stack. */
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str r12, [lr, #PSREG] /* proc_ptr->p_reg.psr = r12. */
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.endm
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.macro exception_handler exc_name, exc_num, lr_offset
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ENTRY(\exc_name\()_entry)
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switch_to_svc \lr_offset
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test_int_in_kernel \exc_name\()_entry_nested
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\exc_name\()entry_from_user:
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save_process_ctx
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ldr fp, [sp] /* save the pointer to the current process. */
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add r4, fp, #PCREG /* save the exception pc (saved lr_user) */
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/* r4-r9 are callee save. */
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/* stop user process cycles */
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mov r0, fp /* first param: caller proc ptr. */
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mov fp, #0 /* for stack trace. */
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bl _C_LABEL(context_stop)
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/*
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* push a pointer to the interrupt state pushed by the cpu and the
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* vector number pushed by the vector handler just before calling
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* exception_entry and call the exception handler.
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*/
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mov r0, #0 /* it is not a nested exception. */
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mov r1, r4 /* saved lr. */
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mov r2, #\exc_num /* vector number */
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bl _C_LABEL(exception_handler)
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b _C_LABEL(switch_to_user)
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\exc_name\()_entry_nested:
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push {r0-r12, lr}
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mov r0, #1 /* it is a nested exception. */
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add r1, sp, #56 /* saved lr */
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mov r2, #\exc_num /* vector number */
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bl _C_LABEL(exception_handler)
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pop {r0-r12, lr}
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rfeia sp!
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.endm
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/* Exception handlers */
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exception_handler data_abort DATA_ABORT_VECTOR 8
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exception_handler prefetch_abort PREFETCH_ABORT_VECTOR 4
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exception_handler undefined_inst UNDEFINED_INST_VECTOR 4
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ENTRY(irq_entry)
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switch_to_svc 4
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test_int_in_kernel irq_entry_from_kernel
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irq_entry_from_user:
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save_process_ctx
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/* save the pointer to the current process */
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ldr fp, [sp]
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push {fp} /* save caller proc ptr. */
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sub sp, sp, #4 /* maintain stack alignment. */
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/* stop user process cycles */
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mov r0, fp /* first param: caller proc ptr. */
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mov fp, #0 /* for stack trace. */
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bl _C_LABEL(context_stop)
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/* call handler */
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bl _C_LABEL(bsp_irq_handle) /* bsp_irq_handle(void) */
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add sp, sp, #4
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pop {fp} /* caller proc ptr. */
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dsb /* data synchronization barrier. */
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b _C_LABEL(switch_to_user)
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irq_entry_from_kernel:
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push {r0-r12, lr}
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bl _C_LABEL(context_stop_idle)
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/* call handler */
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bl _C_LABEL(bsp_irq_handle) /* bsp_irq_handle(void). */
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/* data synchronization barrier */ dsb
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pop {r0-r12, lr}
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rfeia sp!
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/*
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* supervisor call (SVC) kernel entry point
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*/
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ENTRY(svc_entry)
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/* Store the LR and the SPSR of the current mode onto the SVC stack */
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srsdb sp!, #PSR_SVC32_MODE
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save_process_ctx
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/* save the pointer to the current process */
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ldr fp, [sp]
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cmp r3, #KERVEC_INTR
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beq kernel_call_entry
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cmp r3, #IPCVEC_INTR
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beq ipc_entry
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/* return -1 to the current process as an invalid SWI was called .*/
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mov r0, #-1
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str r0, [fp, #REG0]
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b _C_LABEL(switch_to_user)
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/*
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* kernel call is only from a process to kernel
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*/
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ENTRY(kernel_call_entry)
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/*
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* pass the syscall arguments from userspace to the handler.
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* save_process_ctx() does not clobber these registers, they are still
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* set as the userspace has set them.
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*/
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push {fp} /* save caller proc ptr. */
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push {r0} /* save msg ptr so it's not clobbered. */
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/* stop user process cycles */
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mov r0, fp /* first param: caller proc ptr */
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mov fp, #0 /* for stack trace */
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bl _C_LABEL(context_stop)
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pop {r0} /* first param: msg ptr. */
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pop {r1} /* second param: caller proc ptr. */
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bl _C_LABEL(kernel_call)
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b _C_LABEL(switch_to_user)
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/*
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* IPC is only from a process to kernel
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*/
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ENTRY(ipc_entry)
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/*
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* pass the syscall arguments from userspace to the handler.
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* save_process_ctx() does not clobber these registers, they are still
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* set as the userspace have set them
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*/
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push {fp} /* save caller proc ptr. */
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push {r0-r2} /* save regs so they're not clobbered. */
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/* stop user process cycles */
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mov r0, fp /* first param: caller proc ptr. */
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mov fp, #0 /* for stack trace. */
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bl _C_LABEL(context_stop)
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pop {r0-r2} /* restore regs */
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bl _C_LABEL(do_ipc)
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/* restore the current process pointer and save the return value */
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pop {fp} /* caller proc ptr. */
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str r0, [fp, #REG0]
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b _C_LABEL(switch_to_user)
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ENTRY(invalid_svc)
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b .
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ENTRY(restore_user_context)
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/* sp holds the proc ptr */
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mov sp, r0
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/* Set SPSR and LR for return */
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ldr r0, [sp, #PSREG]
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msr spsr_fsxc, r0 /* flags , status, extension control. */
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ldr lr, [sp, #PCREG]
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/* Restore user-mode registers from proc struct */
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ldm sp, {r0-r14}^
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ldr sp, =_C_LABEL(svc_stack)
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ldr sp, [sp]
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/* To user mode! */
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movs pc, lr /* preferred way of returning from svc */
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/*===========================================================================*/
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/* data */
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/*===========================================================================*/
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.data
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.short 0x526F /* this must be the first data entry (magic #) */
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.bss
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.data
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.balign 4
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k_initial_stack:
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.space K_STACK_SIZE
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LABEL(__k_unpaged_k_initial_stktop)
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/*
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* the kernel stack
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*/
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k_boot_stack:
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.space K_STACK_SIZE /* kernel stack */ /* FIXME use macro here */
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LABEL(k_boot_stktop) /* top of kernel stack */
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.balign K_STACK_SIZE
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LABEL(k_stacks_start)
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/* two pages for each stack, one for data, other as a sandbox */
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.space 2 * (K_STACK_SIZE * CONFIG_MAX_CPUS)
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LABEL(k_stacks_end)
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/* top of kernel stack */
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