arm-refactor:document ARM assembly code.
Change-Id: I8540a09cdaf45431ad163954ce41d36f4b72cad5
This commit is contained in:
Kees Jongenburger
parent
9dec6c12f1
commit
3df19a0671
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@ -28,20 +28,20 @@ MINIX:
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b multiboot_init
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multiboot_init:
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ldr sp, =load_stack_start /* make usable stack */
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ldr sp, =load_stack_start /* make usable stack */
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mov fp, #0
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bl _C_LABEL(pre_init)
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/* Kernel is mapped high now and ready to go, with
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* the boot info pointer returned in r0. Set the
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* highly mapped stack, initialize it, push the boot
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* info pointer and jump to the highly mapped kernel.
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* the boot info pointer returned by pre_init in r0.
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* Set the highly mapped stack and initialize it.
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*
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* Afther that call kmain with r0 still pointing to boot info
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*/
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ldr sp, =k_initial_stktop
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mov r1, #0
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push {r1} /* Terminate stack */
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/* r0 holds kinfo_t ptr */
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ldr r2, =_C_LABEL(kmain)
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push {r1} /* Terminate stack */
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ldr r2, =_C_LABEL(kmain) /* r0 holds kinfo_t ptr */
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bx r2
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/* not reached */
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@ -34,42 +34,52 @@
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IMPORT(svc_stack)
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/*
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* Adjust lr, switch to SVC mode, and push pc/psr when exception triggered
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* The 'lr_offset' argument holds the adjustment. It differs based on
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* which mode the CPU is in.
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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
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srsdb sp!, #MODE_SVC
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cps #MODE_SVC
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sub lr, lr, #\lr_offset /* do the adjustment */
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srsdb sp!, #MODE_SVC /* 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 #MODE_SVC /* do the switch to SVC. */
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.endm
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/*
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* Test if the exception/interrupt occured in the kernel.
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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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*/
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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] /* spsr */
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orr r3, r3, #(PSR_F | PSR_I) /* mask interrupts on return */
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str r3, [sp, #8] /* spsr */
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and r3, r3, #PSR_MODE_MASK
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cmp r3, #MODE_USR
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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 /* mask the ARM mode. */
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cmp r3, #MODE_USR /* compare it to user mode. */
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pop {r3}
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bne \label /* In-kernel handling */
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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 /* srsdb pushed cpsr and pc on the stack */
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ldr lr, [sp] /* lr = proc_ptr */
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stm lr, {r0-r14}^ /* 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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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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@ -80,14 +90,13 @@ ENTRY(\exc_name\()_entry)
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\exc_name\()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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/* save the exception pc (saved lr_user) */
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add r4, fp, #PCREG
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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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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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@ -95,17 +104,16 @@ ENTRY(\exc_name\()_entry)
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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's not a nested exception */
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mov r1, r4 /* saved lr */
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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's a nested exception */
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add r1, sp, #56 /* saved 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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@ -129,22 +137,20 @@ irq_entry_from_user:
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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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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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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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/* data synchronization barrier */
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dsb
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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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@ -153,11 +159,9 @@ irq_entry_from_kernel:
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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 */
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dsb
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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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@ -166,6 +170,7 @@ irq_entry_from_kernel:
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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!, #MODE_SVC
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save_process_ctx
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@ -187,20 +192,20 @@ ENTRY(svc_entry)
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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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* 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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* 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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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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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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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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@ -214,19 +219,19 @@ ENTRY(ipc_entry)
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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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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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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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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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@ -240,7 +245,7 @@ ENTRY(restore_user_context)
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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
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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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@ -250,7 +255,7 @@ ENTRY(restore_user_context)
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ldr sp, [sp]
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/* To user mode! */
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movs pc, lr
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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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@ -75,6 +75,7 @@ int booting_cpu = 0;
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void prot_init()
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{
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/* tell the HW where we stored our vector table */
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write_vbar((reg_t)&exc_vector_table);
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/* Set up a new post-relocate bootstrap pagetable so that
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