From 9cc8ba53f694dd7e2c2255e0caaa264bfa39a6fa Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Wed, 1 Sep 2004 21:43:20 +0000 Subject: [PATCH] Clean up interrupts.[ch]. --- src/threads/interrupt.c | 428 ++++++++++++++++++++++++---------------- src/threads/interrupt.h | 2 - 2 files changed, 263 insertions(+), 167 deletions(-) diff --git a/src/threads/interrupt.c b/src/threads/interrupt.c index 9020b0e..268e3b5 100644 --- a/src/threads/interrupt.c +++ b/src/threads/interrupt.c @@ -8,7 +8,44 @@ #include "mmu.h" #include "thread.h" #include "timer.h" + +/* Number of x86 interrupts. */ +#define INTR_CNT 256 + +/* The Interrupt Descriptor Table (IDT). The format is fixed by + the CPU. See [IA32-v3] sections 5.10, 5.11, 5.12.1.2. */ +static uint64_t idt[INTR_CNT]; + +/* Interrupt handler functions for each interrupt. */ +static intr_handler_func *intr_handlers[INTR_CNT]; + +/* Names for each interrupt, for debugging purposes. */ +static const char *intr_names[INTR_CNT]; + +/* External interrupts are those generated by devices outside the + CPU, such as the timer. External interrupts run with + interrupts turned off, so they never nest, nor are they ever + pre-empted. Handlers for external interrupts also may not + sleep, although they may invoke intr_yield_on_return() to + request that a new process be scheduled just before the + interrupt returns. */ +static bool in_external_intr; /* Are we processing an external interrupt? */ +static bool yield_on_return; /* Should we yield on interrupt return? */ + +/* Programmable Interrupt Controller helpers. */ +static void pic_init (void); +static void pic_end_of_interrupt (int irq); + +/* Interrupt Descriptor Table helpers. */ +static uint64_t make_intr_gate (void (*) (void), int dpl); +static uint64_t make_trap_gate (void (*) (void), int dpl); + +/* Interrupt handlers. */ +void intr_handler (struct intr_frame *args); +static intr_handler_func panic NO_RETURN; +static intr_handler_func kill NO_RETURN; +/* Returns the current interrupt status. */ enum intr_level intr_get_level (void) { @@ -16,20 +53,18 @@ intr_get_level (void) asm ("pushfl; popl %0" : "=g" (flags)); - return flags & (1 << 9) ? INTR_ON : INTR_OFF; + return flags & FLAG_IF ? INTR_ON : INTR_OFF; } +/* Enables or disables interrupts as specified by LEVEL and + returns the previous interrupt status. */ enum intr_level intr_set_level (enum intr_level level) { - enum intr_level old_level = intr_get_level (); - if (level == INTR_ON) - intr_enable (); - else - intr_disable (); - return old_level; + return level == INTR_ON ? intr_enable () : intr_disable (); } +/* Enables interrupts and returns the previous interrupt status. */ enum intr_level intr_enable (void) { @@ -38,6 +73,7 @@ intr_enable (void) return old_level; } +/* Disables interrupts and returns the previous interrupt status. */ enum intr_level intr_disable (void) { @@ -46,23 +82,122 @@ intr_disable (void) return old_level; } +/* Initializes the interrupt system. */ +void +intr_init (void) +{ + uint64_t idtr_operand; + int i; + + pic_init (); + + /* Initialize intr_names. */ + for (i = 0; i < INTR_CNT; i++) + intr_names[i] = "unknown"; + + /* Most exceptions require ring 0. + Exceptions 3, 4, and 5 can be caused by ring 3 directly. */ + intr_register (0, 0, INTR_ON, kill, "#DE Divide Error"); + intr_register (1, 0, INTR_ON, kill, "#DB Debug Exception"); + intr_register (2, 0, INTR_ON, panic, "NMI Interrupt"); + intr_register (3, 3, INTR_ON, kill, "#BP Breakpoint Exception"); + intr_register (4, 3, INTR_ON, kill, "#OF Overflow Exception"); + intr_register (5, 3, INTR_ON, kill, "#BR BOUND Range Exceeded Exception"); + intr_register (6, 0, INTR_ON, kill, "#UD Invalid Opcode Exception"); + intr_register (7, 0, INTR_ON, kill, "#NM Device Not Available Exception"); + intr_register (8, 0, INTR_ON, panic, "#DF Double Fault Exception"); + intr_register (9, 0, INTR_ON, panic, "Coprocessor Segment Overrun"); + intr_register (10, 0, INTR_ON, panic, "#TS Invalid TSS Exception"); + intr_register (11, 0, INTR_ON, kill, "#NP Segment Not Present"); + intr_register (12, 0, INTR_ON, kill, "#SS Stack Fault Exception"); + intr_register (13, 0, INTR_ON, kill, "#GP General Protection Exception"); + intr_register (16, 0, INTR_ON, kill, "#MF x87 FPU Floating-Point Error"); + intr_register (17, 0, INTR_ON, panic, "#AC Alignment Check Exception"); + intr_register (18, 0, INTR_ON, panic, "#MC Machine-Check Exception"); + intr_register (19, 0, INTR_ON, kill, "#XF SIMD Floating-Point Exception"); + + /* Most exceptions can be handled with interrupts turned on. + We need to disable interrupts for page faults because the + fault address is stored in CR2 and needs to be preserved. */ + intr_register (14, 0, INTR_OFF, kill, "#PF Page-Fault Exception"); + + idtr_operand = make_dtr_operand (sizeof idt - 1, idt); + asm volatile ("lidt %0" :: "m" (idtr_operand)); +} + +/* Registers interrupt VEC_NO to invoke HANDLER, which is named + NAME for debugging purposes. The interrupt handler will be + invoked with interrupt status set to LEVEL. + + The handler will have descriptor privilege level DPL, meaning + that it can be invoked intentionally when the processor is in + the DPL or lower-numbered ring. In practice, DPL==3 allows + user mode to invoke the interrupts and DPL==0 prevents such + invocation. Faults and exceptions that occur in user mode + still cause interrupts with DPL==0 to be invoked. See + [IA32-v3] sections 4.5 and 4.8.1.1 for further discussion. */ +void +intr_register (uint8_t vec_no, int dpl, enum intr_level level, + intr_handler_func *handler, + const char *name) +{ + /* Make sure this handler isn't already registered to someone + else. */ + ASSERT (intr_handlers[vec_no] == NULL); + + /* Interrupts generated by external hardware (0x20 <= VEC_NO <= + 0x2f) should specify INTR_OFF for LEVEL. Otherwise a timer + interrupt could cause a task switch during interrupt + handling. Most other interrupts can and should be handled + with interrupts enabled. */ + ASSERT (vec_no < 0x20 || vec_no > 0x2f || level == INTR_OFF); + + if (level == INTR_ON) + idt[vec_no] = make_trap_gate (intr_stubs[vec_no], dpl); + else + idt[vec_no] = make_intr_gate (intr_stubs[vec_no], dpl); + intr_handlers[vec_no] = handler; + intr_names[vec_no] = name; +} + +/* Returns true during processing of an external interrupt + and false at all other times. */ +bool +intr_context (void) +{ + return in_external_intr; +} + +/* During processing of an external interrupt, directs the + interrupt handler to yield to a new process just before + returning from the interrupt. May not be called at any other + time. */ +void +intr_yield_on_return (void) +{ + ASSERT (intr_context ()); + yield_on_return = true; +} + +/* 8259A Programmable Interrupt Controller. */ + +/* Every PC has two 8259A Programmable Interrupt Controller (PIC) + chips. One is a "master" accessible at ports 0x20 and 0x21. + The other is a "slave" cascaded onto the master's IRQ 2 line + and accessible at ports 0xa0 and 0xa1. Accesses to port 0x20 + set the A0 line to 0 and accesses to 0x21 set the A1 line to + 1. The situation is similar for the slave PIC. + + By default, interrupts 0...15 delivered by the PICs will go to + interrupt vectors 0...15. Unfortunately, those vectors are + also used for CPU traps and exceptions. We reprogram the PICs + so that interrupts 0...15 are delivered to interrupt vectors + 32...47 (0x20...0x2f) instead. */ + +/* Initializes the PICs. Refer to [8259A] for details. */ static void pic_init (void) { - /* Every PC has two 8259A Programmable Interrupt Controller - (PIC) chips. One is a "master" accessible at ports 0x20 and - 0x21. The other is a "slave" cascaded onto the master's IRQ - 2 line and accessible at ports 0xa0 and 0xa1. Accesses to - port 0x20 set the A0 line to 0 and accesses to 0x21 set the - A1 line to 1. The situation is similar for the slave PIC. - Refer to the 8259A datasheet for details. - - By default, interrupts 0...15 delivered by the PICs will go - to interrupt vectors 0...15. Unfortunately, those vectors - are also used for CPU traps and exceptions. We reprogram - the PICs so that interrupts 0...15 are delivered to - interrupt vectors 32...47 instead. */ - /* Mask all interrupts on both PICs. */ outb (0x21, 0xff); outb (0xa1, 0xff); @@ -85,84 +220,40 @@ pic_init (void) } /* Sends an end-of-interrupt signal to the PIC for the given IRQ. - If we don't acknowledge the IRQ, we'll never get it again, so - this is important. */ + If we don't acknowledge the IRQ, it will never be delivered to + us again, so this is important. */ static void -pic_eoi (int irq) +pic_end_of_interrupt (int irq) { - /* FIXME? The Linux code is much more complicated. */ ASSERT (irq >= 0x20 && irq < 0x30); + + /* Acknowledge master PIC. */ outb (0x20, 0x20); + + /* Acknowledge slave PIC if this is a slave interrupt. */ if (irq >= 0x28) outb (0xa0, 0x20); } -#define INTR_CNT 256 - -static uint64_t idt[INTR_CNT]; -static intr_handler_func *intr_handlers[INTR_CNT]; -static const char *intr_names[INTR_CNT]; - -void intr_handler (struct intr_frame *args); - -static bool intr_in_progress; -static bool yield_on_return; - -const char * -intr_name (int vec) -{ - if (vec < 0 || vec >= INTR_CNT || intr_names[vec] == NULL) - return "unknown"; - else - return intr_names[vec]; -} - -void -intr_handler (struct intr_frame *args) -{ - bool external = args->vec_no >= 0x20 && args->vec_no < 0x30; - if (external) - { - ASSERT (intr_get_level () == INTR_OFF); - ASSERT (!intr_context ()); - intr_in_progress = true; - yield_on_return = false; - } - - intr_handlers[args->vec_no] (args); - - if (external) - { - ASSERT (intr_get_level () == INTR_OFF); - ASSERT (intr_context ()); - intr_in_progress = false; - pic_eoi (args->vec_no); - - if (yield_on_return) - thread_yield (); - } -} - -bool -intr_context (void) -{ - return intr_in_progress; -} - -void -intr_yield_on_return (void) -{ - ASSERT (intr_context ()); - yield_on_return = true; -} - -static intr_handler_func panic NO_RETURN; -static intr_handler_func kill NO_RETURN; - +/* Creates an gate that invokes FUNCTION. + + The gate has descriptor privilege level DPL, meaning that it + can be invoked intentionally when the processor is in the DPL + or lower-numbered ring. In practice, DPL==3 allows user mode + to call into the gate and DPL==0 prevents such calls. Faults + and exceptions that occur in user mode still cause gates with + DPL==0 to be invoked. See [IA32-v3] sections 4.5 and 4.8.1.1 + for further discussion. + + TYPE must be either TYPE_INT_32 (for an interrupt gate) or + TYPE_TRAP_32 (for a trap gate). The difference is that + entering an interrupt gate disables interrupts, but entering a + trap gate does not. See [IA32-v3] section 5.12.1.2 for + discussion. */ static uint64_t -make_gate (void (*target) (void), int dpl, enum seg_type type) +make_gate (void (*function) (void), int dpl, enum seg_type type) { - uint32_t offset = (uint32_t) target; + uint32_t offset = (uint32_t) function; uint32_t e0 = ((offset & 0xffff) /* Offset 15:0. */ | (SEL_KCSEG << 16)); /* Target code segment. */ uint32_t e1 = ((offset & 0xffff0000) /* Offset 31:16. */ @@ -173,98 +264,69 @@ make_gate (void (*target) (void), int dpl, enum seg_type type) return e0 | ((uint64_t) e1 << 32); } +/* Creates an interrupt gate that invokes FUNCTION with the given + DPL. */ static uint64_t -make_intr_gate (void (*target) (void), int dpl) +make_intr_gate (void (*function) (void), int dpl) { - return make_gate (target, dpl, TYPE_INT_32); + return make_gate (function, dpl, TYPE_INT_32); } +/* Creates a trap gate that invokes FUNCTION with the given + DPL. */ static uint64_t -make_trap_gate (void (*target) (void), int dpl) +make_trap_gate (void (*function) (void), int dpl) { - return make_gate (target, dpl, TYPE_TRAP_32); + return make_gate (function, dpl, TYPE_TRAP_32); } + +/* Interrupt handlers. */ -void -intr_register (uint8_t vec_no, int dpl, enum intr_level level, - intr_handler_func *handler, - const char *name) -{ - /* Interrupts generated by external hardware (0x20 <= VEC_NO <= - 0x2f) should specify INTR_OFF for LEVEL. Otherwise a timer - interrupt could cause a task switch during interrupt - handling. Most other interrupts can and should be handled - with interrupts enabled. */ - ASSERT (vec_no < 0x20 || vec_no > 0x2f || level == INTR_OFF); - - if (level == INTR_ON) - idt[vec_no] = make_trap_gate (intr_stubs[vec_no], dpl); - else - idt[vec_no] = make_intr_gate (intr_stubs[vec_no], dpl); - intr_handlers[vec_no] = handler; - intr_names[vec_no] = name; -} +static void dump_intr_frame (struct intr_frame *); +/* Handler for all interrupts, faults, and exceptions. This + function is called by the assembly language interrupt stubs in + intr-stubs.S (see intr-stubs.pl). ARGS describes the + interrupt and the interrupted thread's registers. */ void -intr_init (void) +intr_handler (struct intr_frame *args) { - uint64_t idtr_operand; - int i; - - pic_init (); + bool external; + intr_handler_func *handler; - /* Install default handlers. */ - for (i = 0; i < 256; i++) - intr_register (i, 0, INTR_OFF, panic, NULL); + external = args->vec_no >= 0x20 && args->vec_no < 0x30; + if (external) + { + ASSERT (intr_get_level () == INTR_OFF); + ASSERT (!intr_context ()); - /* Most exceptions require ring 0. - Exceptions 3, 4, and 5 can be caused by ring 3 directly. */ - intr_register (0, 0, INTR_ON, kill, "#DE Divide Error"); - intr_register (1, 0, INTR_ON, kill, "#DB Debug Exception"); - intr_register (2, 0, INTR_ON, panic, "NMI Interrupt"); - intr_register (3, 3, INTR_ON, kill, "#BP Breakpoint Exception"); - intr_register (4, 3, INTR_ON, kill, "#OF Overflow Exception"); - intr_register (5, 3, INTR_ON, kill, "#BR BOUND Range Exceeded Exception"); - intr_register (6, 0, INTR_ON, kill, "#UD Invalid Opcode Exception"); - intr_register (7, 0, INTR_ON, kill, "#NM Device Not Available Exception"); - intr_register (8, 0, INTR_ON, panic, "#DF Double Fault Exception"); - intr_register (9, 0, INTR_ON, panic, "Coprocessor Segment Overrun"); - intr_register (10, 0, INTR_ON, panic, "#TS Invalid TSS Exception"); - intr_register (11, 0, INTR_ON, kill, "#NP Segment Not Present"); - intr_register (12, 0, INTR_ON, kill, "#SS Stack Fault Exception"); - intr_register (13, 0, INTR_ON, kill, "#GP General Protection Exception"); - intr_register (16, 0, INTR_ON, kill, "#MF x87 FPU Floating-Point Error"); - intr_register (17, 0, INTR_ON, panic, "#AC Alignment Check Exception"); - intr_register (18, 0, INTR_ON, panic, "#MC Machine-Check Exception"); - intr_register (19, 0, INTR_ON, kill, "#XF SIMD Floating-Point Exception"); + in_external_intr = true; + yield_on_return = false; + } - /* Most exceptions can be handled with interrupts turned on. - We need to disable interrupts for page faults because the - fault address is stored in CR2 and needs to be preserved. */ - intr_register (14, 0, INTR_OFF, kill, "#PF Page-Fault Exception"); + /* Invoke the interrupt's handler. + If there is no handler, invoke the unexpected interrupt + handler. */ + handler = intr_handlers[args->vec_no]; + if (handler == NULL) + handler = panic; + handler (args); - idtr_operand = make_dtr_operand (sizeof idt - 1, idt); - asm volatile ("lidt %0" :: "m" (idtr_operand)); -} + /* Complete the processing of an external interrupt. */ + if (external) + { + ASSERT (intr_get_level () == INTR_OFF); + ASSERT (intr_context ()); -static void -dump_intr_frame (struct intr_frame *f) -{ - uint32_t cr2, ss; - asm ("movl %%cr2, %0" : "=r" (cr2)); - asm ("movl %%ss, %0" : "=r" (ss)); + in_external_intr = false; + pic_end_of_interrupt (args->vec_no); - printk ("Interrupt %#04x (%s) at eip=%p\n", - f->vec_no, intr_name (f->vec_no), f->eip); - printk (" cr2=%08"PRIx32" error=%08"PRIx32"\n", cr2, f->error_code); - printk (" eax=%08"PRIx32" ebx=%08"PRIx32" ecx=%08"PRIx32" edx=%08"PRIx32"\n", - f->eax, f->ebx, f->ecx, f->edx); - printk (" esi=%08"PRIx32" edi=%08"PRIx32" esp=%08"PRIx32" ebp=%08"PRIx32"\n", - f->esi, f->edi, (uint32_t) f->esp, f->ebp); - printk (" cs=%04"PRIx16" ds=%04"PRIx16" es=%04"PRIx16" ss=%04"PRIx16"\n", - f->cs, f->ds, f->es, f->cs != SEL_KCSEG ? f->ss : ss); + if (yield_on_return) + thread_yield (); + } } +/* Handler for an interrupt that should not have been invoked. */ static void panic (struct intr_frame *regs) { @@ -272,27 +334,63 @@ panic (struct intr_frame *regs) PANIC ("Panic!"); } +/* Handler for an exception (probably) caused by a user process. */ static void kill (struct intr_frame *f) { + /* This interrupt is one (probably) caused by a user process. + For example, the process might have tried to access unmapped + virtual memory (a page fault). For now, we simply kill the + user process. Later, we'll want to handle page faults in + the kernel. Real Unix-like operating systems pass most + exceptions back to the process via signals, but we don't + implement them. */ + + /* The interrupt frame's code segment value tells us where the + exception originated. */ switch (f->cs) { case SEL_UCSEG: + /* User's code segment, so it's a user exception, as we + expected. */ printk ("%s: dying due to interrupt %#04x (%s).\n", thread_name (thread_current ()), - f->vec_no, intr_name (f->vec_no)); + f->vec_no, intr_names[f->vec_no]); dump_intr_frame (f); thread_exit (); case SEL_KCSEG: - printk ("Kernel bug - unexpected interrupt in kernel context\n"); + /* Kernel's code segment, which indicates a kernel bug. + Kernel code shouldn't throw exceptions. (Page faults + may cause kernel exceptions--but they shouldn't arrive + here.) */ + printk ("Kernel bug - unexpected interrupt in kernel\n"); panic (f); default: + /* Some other code segment? Shouldn't happen. */ printk ("Interrupt %#04x (%s) in unknown segment %04x\n", - f->vec_no, intr_name (f->vec_no), f->cs); + f->vec_no, intr_names[f->vec_no], f->cs); thread_exit (); } } +/* Dumps interrupt frame F to the console, for debugging. */ +static void +dump_intr_frame (struct intr_frame *f) +{ + uint32_t cr2, ss; + asm ("movl %%cr2, %0" : "=r" (cr2)); + asm ("movl %%ss, %0" : "=r" (ss)); + + printk ("Interrupt %#04x (%s) at eip=%p\n", + f->vec_no, intr_names[f->vec_no], f->eip); + printk (" cr2=%08"PRIx32" error=%08"PRIx32"\n", cr2, f->error_code); + printk (" eax=%08"PRIx32" ebx=%08"PRIx32" ecx=%08"PRIx32" edx=%08"PRIx32"\n", + f->eax, f->ebx, f->ecx, f->edx); + printk (" esi=%08"PRIx32" edi=%08"PRIx32" esp=%08"PRIx32" ebp=%08"PRIx32"\n", + f->esi, f->edi, (uint32_t) f->esp, f->ebp); + printk (" cs=%04"PRIx16" ds=%04"PRIx16" es=%04"PRIx16" ss=%04"PRIx16"\n", + f->cs, f->ds, f->es, f->cs != SEL_KCSEG ? f->ss : ss); +} diff --git a/src/threads/interrupt.h b/src/threads/interrupt.h index 7084bf1..fe26b3d 100644 --- a/src/threads/interrupt.h +++ b/src/threads/interrupt.h @@ -56,6 +56,4 @@ void intr_register (uint8_t vec, int dpl, enum intr_level, intr_handler_func *, bool intr_context (void); void intr_yield_on_return (void); -const char *intr_name (int vec); - #endif /* interrupt.h */ -- 2.30.2