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  1. /*
  2.  * Copyright (c) 2007 Petr Stepan
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup arm32
  30.  * @{
  31.  */
  32. /** @file
  33.  *  @brief Exception handlers and exception initialization routines.
  34.  */
  35.  
  36. #include <arch/exception.h>
  37. #include <arch/debug/print.h>
  38. #include <arch/memstr.h>
  39. #include <arch/regutils.h>
  40. #include <interrupt.h>
  41. #include <arch/machine.h>
  42. #include <arch/mm/page_fault.h>
  43. #include <arch/barrier.h>
  44. #include <print.h>
  45. #include <syscall/syscall.h>
  46.  
  47. /** Offset used in calculation of exception handler's relative address.
  48.  *
  49.  * @see install_handler()
  50.  */
  51. #define PREFETCH_OFFSET      0x8
  52.  
  53. /** LDR instruction's code */
  54. #define LDR_OPCODE           0xe59ff000
  55.  
  56. /** Number of exception vectors. */
  57. #define EXC_VECTORS          8
  58.  
  59. /** Size of memory block occupied by exception vectors. */
  60. #define EXC_VECTORS_SIZE     (EXC_VECTORS * 4)
  61.  
  62. /** Switches to kernel stack and saves all registers there.
  63.  *
  64.  * Temporary exception stack is used to save a few registers
  65.  * before stack switch takes place.
  66.  */
  67. inline static void setup_stack_and_save_regs()
  68. {
  69.     asm volatile(
  70.         "ldr r13, =exc_stack        \n"
  71.         "stmfd r13!, {r0}       \n"
  72.         "mrs r0, spsr           \n"
  73.         "and r0, r0, #0x1f      \n"
  74.         "cmp r0, #0x10          \n"
  75.         "bne 1f             \n"
  76.  
  77.         /* prev mode was usermode */
  78.         "ldmfd r13!, {r0}       \n"
  79.         "ldr r13, =supervisor_sp    \n"
  80.         "ldr r13, [r13]         \n"
  81.         "stmfd r13!, {lr}       \n"
  82.         "stmfd r13!, {r0-r12}       \n"
  83.         "stmfd r13!, {r13, lr}^     \n"
  84.         "mrs r0, spsr           \n"
  85.         "stmfd r13!, {r0}       \n"
  86.         "b 2f               \n"
  87.  
  88.         /* mode was not usermode */
  89.     "1:\n"
  90.         "stmfd r13!, {r1, r2, r3}   \n"
  91.         "mrs r1, cpsr           \n"
  92.         "mov r2, lr         \n"
  93.         "bic r1, r1, #0x1f      \n"
  94.         "orr r1, r1, r0         \n"
  95.         "mrs r0, cpsr           \n"
  96.         "msr cpsr_c, r1         \n"
  97.  
  98.         "mov r3, r13            \n"
  99.         "stmfd r13!, {r2}       \n"
  100.         "mov r2, lr         \n"
  101.         "stmfd r13!, {r4-r12}       \n"
  102.         "mov r1, r13            \n"
  103.         /* the following two lines are for debugging */
  104.         "mov sp, #0         \n"
  105.         "mov lr, #0         \n"
  106.         "msr cpsr_c, r0         \n"
  107.  
  108.         "ldmfd r13!, {r4, r5, r6, r7}   \n"
  109.         "stmfd r1!, {r4, r5, r6}    \n"
  110.         "stmfd r1!, {r7}        \n"
  111.         "stmfd r1!, {r2}        \n"
  112.         "stmfd r1!, {r3}        \n"
  113.         "mrs r0, spsr           \n"
  114.         "stmfd r1!, {r0}        \n"
  115.         "mov r13, r1            \n"
  116.     "2:\n"
  117.     );
  118. }
  119.  
  120. /** Returns from exception mode.
  121.  *
  122.  * Previously saved state of registers (including control register)
  123.  * is restored from the stack.
  124.  */
  125. inline static void load_regs()
  126. {
  127.     asm volatile(
  128.         "ldmfd r13!, {r0}       \n"
  129.         "msr spsr, r0           \n"
  130.         "and r0, r0, #0x1f      \n"
  131.         "cmp r0, #0x10          \n"
  132.         "bne 1f             \n"
  133.  
  134.         /* return to user mode */
  135.         "ldmfd r13!, {r13, lr}^     \n"
  136.         "b 2f               \n"
  137.  
  138.         /* return to non-user mode */
  139.     "1:\n"
  140.         "ldmfd r13!, {r1, r2}       \n"
  141.         "mrs r3, cpsr           \n"
  142.         "bic r3, r3, #0x1f      \n"
  143.         "orr r3, r3, r0         \n"
  144.         "mrs r0, cpsr           \n"
  145.         "msr cpsr_c, r3         \n"
  146.  
  147.         "mov r13, r1            \n"
  148.         "mov lr, r2         \n"
  149.         "msr cpsr_c, r0         \n"
  150.  
  151.         /* actual return */
  152.     "2:\n"
  153.         "ldmfd r13, {r0-r12, pc}^\n"
  154.     );
  155. }
  156.  
  157.  
  158. /** Switch CPU to mode in which interrupts are serviced (currently it
  159.  * is Undefined mode).
  160.  *
  161.  * The default mode for interrupt servicing (Interrupt Mode)
  162.  * can not be used because of nested interrupts (which can occur
  163.  * because interrupts are enabled in higher levels of interrupt handler).
  164.  */
  165. inline static void switch_to_irq_servicing_mode()
  166. {
  167.     /* switch to Undefined mode */
  168.     asm volatile(
  169.         /* save regs used during switching */
  170.         "stmfd sp!, {r0-r3}     \n"
  171.  
  172.         /* save stack pointer and link register to r1, r2 */
  173.         "mov r1, sp         \n"
  174.         "mov r2, lr         \n"
  175.  
  176.         /* mode switch */
  177.         "mrs r0, cpsr           \n"
  178.         "bic r0, r0, #0x1f      \n"
  179.         "orr r0, r0, #0x1b      \n"
  180.         "msr cpsr_c, r0         \n"
  181.  
  182.         /* restore saved sp and lr */
  183.         "mov sp, r1         \n"
  184.         "mov lr, r2         \n"
  185.  
  186.         /* restore original regs */
  187.         "ldmfd sp!, {r0-r3}     \n"
  188.     );
  189. }
  190.  
  191. /** Calls exception dispatch routine. */
  192. #define CALL_EXC_DISPATCH(exception)        \
  193.     asm("mov r0, %0" : : "i" (exception));  \
  194.     asm("mov r1, r13");         \
  195.     asm("bl exc_dispatch");    
  196.  
  197. /** General exception handler.
  198.  *
  199.  *  Stores registers, dispatches the exception,
  200.  *  and finally restores registers and returns from exception processing.
  201.  *
  202.  *  @param exception Exception number.
  203.  */
  204. #define PROCESS_EXCEPTION(exception)        \
  205.     setup_stack_and_save_regs();        \
  206.     CALL_EXC_DISPATCH(exception)        \
  207.     load_regs();
  208.  
  209. /** Updates specified exception vector to jump to given handler.
  210.  *
  211.  *  Addresses of handlers are stored in memory following exception vectors.
  212.  */
  213. static void install_handler(unsigned handler_addr, unsigned *vector)
  214. {
  215.     /* relative address (related to exc. vector) of the word
  216.      * where handler's address is stored
  217.     */
  218.     volatile uint32_t handler_address_ptr = EXC_VECTORS_SIZE -
  219.         PREFETCH_OFFSET;
  220.    
  221.     /* make it LDR instruction and store at exception vector */
  222.     *vector = handler_address_ptr | LDR_OPCODE;
  223.     smc_coherence(*vector);
  224.    
  225.     /* store handler's address */
  226.     *(vector + EXC_VECTORS) = handler_addr;
  227.  
  228. }
  229.  
  230. /** Low-level Reset Exception handler. */
  231. static void reset_exception_entry(void)
  232. {
  233.     PROCESS_EXCEPTION(EXC_RESET);
  234. }
  235.  
  236. /** Low-level Software Interrupt Exception handler. */
  237. static void swi_exception_entry(void)
  238. {
  239.     PROCESS_EXCEPTION(EXC_SWI);
  240. }
  241.  
  242. /** Low-level Undefined Instruction Exception handler. */
  243. static void undef_instr_exception_entry(void)
  244. {
  245.     PROCESS_EXCEPTION(EXC_UNDEF_INSTR);
  246. }
  247.  
  248. /** Low-level Fast Interrupt Exception handler. */
  249. static void fiq_exception_entry(void)
  250. {
  251.     PROCESS_EXCEPTION(EXC_FIQ);
  252. }
  253.  
  254. /** Low-level Prefetch Abort Exception handler. */
  255. static void prefetch_abort_exception_entry(void)
  256. {
  257.     asm("sub lr, lr, #4");
  258.     PROCESS_EXCEPTION(EXC_PREFETCH_ABORT);
  259. }
  260.  
  261. /** Low-level Data Abort Exception handler. */
  262. static void data_abort_exception_entry(void)
  263. {
  264.     asm("sub lr, lr, #8");
  265.     PROCESS_EXCEPTION(EXC_DATA_ABORT);
  266. }
  267.  
  268. /** Low-level Interrupt Exception handler.
  269.  *
  270.  * CPU is switched to Undefined mode before further interrupt processing
  271.  * because of possible occurence of nested interrupt exception, which
  272.  * would overwrite (and thus spoil) stack pointer.
  273.  */
  274. static void irq_exception_entry(void)
  275. {
  276.     asm("sub lr, lr, #4");
  277.     setup_stack_and_save_regs();
  278.    
  279.     switch_to_irq_servicing_mode();
  280.    
  281.     CALL_EXC_DISPATCH(EXC_IRQ)
  282.  
  283.     load_regs();
  284. }
  285.  
  286. /** Software Interrupt handler.
  287.  *
  288.  * Dispatches the syscall.
  289.  */
  290. static void swi_exception(int exc_no, istate_t *istate)
  291. {
  292.     istate->r0 = syscall_handler(istate->r0, istate->r1, istate->r2,
  293.         istate->r3, istate->r4, istate->r5, istate->r6);
  294. }
  295.  
  296. /** Interrupt Exception handler.
  297.  *
  298.  * Determines the sources of interrupt and calls their handlers.
  299.  */
  300. static void irq_exception(int exc_no, istate_t *istate)
  301. {
  302.     machine_irq_exception(exc_no, istate);
  303. }
  304.  
  305. /** Fills exception vectors with appropriate exception handlers. */
  306. void install_exception_handlers(void)
  307. {
  308.     install_handler((unsigned) reset_exception_entry,
  309.         (unsigned *) EXC_RESET_VEC);
  310.    
  311.     install_handler((unsigned) undef_instr_exception_entry,
  312.         (unsigned *) EXC_UNDEF_INSTR_VEC);
  313.    
  314.     install_handler((unsigned) swi_exception_entry,
  315.         (unsigned *) EXC_SWI_VEC);
  316.    
  317.     install_handler((unsigned) prefetch_abort_exception_entry,
  318.         (unsigned *) EXC_PREFETCH_ABORT_VEC);
  319.    
  320.     install_handler((unsigned) data_abort_exception_entry,
  321.         (unsigned *) EXC_DATA_ABORT_VEC);
  322.    
  323.     install_handler((unsigned) irq_exception_entry,
  324.         (unsigned *) EXC_IRQ_VEC);
  325.    
  326.     install_handler((unsigned)fiq_exception_entry,
  327.         (unsigned *) EXC_FIQ_VEC);
  328. }
  329.  
  330. #ifdef HIGH_EXCEPTION_VECTORS
  331. /** Activates use of high exception vectors addresses. */
  332. static void high_vectors(void)
  333. {
  334.     uint32_t control_reg;
  335.    
  336.     asm volatile("mrc p15, 0, %0, c1, c1" : "=r" (control_reg));
  337.    
  338.     /* switch on the high vectors bit */
  339.     control_reg |= CP15_R1_HIGH_VECTORS_BIT;
  340.    
  341.     asm volatile("mcr p15, 0, %0, c1, c1" : : "r" (control_reg));
  342. }
  343. #endif
  344.  
  345. /** Initializes exception handling.
  346.  *
  347.  * Installs low-level exception handlers and then registers
  348.  * exceptions and their handlers to kernel exception dispatcher.
  349.  */
  350. void exception_init(void)
  351. {
  352. #ifdef HIGH_EXCEPTION_VECTORS
  353.     high_vectors();
  354. #endif
  355.     install_exception_handlers();
  356.    
  357.     exc_register(EXC_IRQ, "interrupt", (iroutine) irq_exception);
  358.     exc_register(EXC_PREFETCH_ABORT, "prefetch abort",
  359.         (iroutine) prefetch_abort);
  360.     exc_register(EXC_DATA_ABORT, "data abort", (iroutine) data_abort);
  361.     exc_register(EXC_SWI, "software interrupt", (iroutine) swi_exception);
  362. }
  363.  
  364. /** Prints #istate_t structure content.
  365.  *
  366.  * @param istate Structure to be printed.
  367.  */
  368. void print_istate(istate_t *istate)
  369. {
  370.     dprintf("istate dump:\n");
  371.  
  372.     dprintf(" r0: %x    r1: %x    r2: %x    r3: %x\n",
  373.         istate->r0, istate->r1, istate->r2, istate->r3);
  374.     dprintf(" r4: %x    r5: %x    r6: %x    r7: %x\n",
  375.         istate->r4, istate->r5, istate->r6, istate->r7);
  376.     dprintf(" r8: %x    r8: %x   r10: %x   r11: %x\n",
  377.         istate->r8, istate->r9, istate->r10, istate->r11);
  378.     dprintf(" r12: %x    sp: %x    lr: %x  spsr: %x\n",
  379.         istate->r12, istate->sp, istate->lr, istate->spsr);
  380.  
  381.     dprintf(" pc: %x\n", istate->pc);
  382. }
  383.  
  384. /** @}
  385.  */
  386.