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thermosphere: properly implement guest timer stuff

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This commit is contained in:
TuxSH 2020-01-12 21:51:50 +00:00
parent 388c245ce4
commit 68a1ce6dd2
12 changed files with 180 additions and 53 deletions
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2
thermosphere/linker.ld
View file

@ -23,6 +23,8 @@ SECTIONS
. = ALIGN(0x800);
__vectors_start__ = ABSOLUTE(.);
KEEP(*(.vectors*));
__vectors_end__ = ABSOLUTE(.);
ASSERT(__vectors_end__ - __vectors_start__ <= 0x800, "Exception vectors section should be max 0x800 in size!");
. = ALIGN(8);
} >main :main

5
thermosphere/src/core_ctx.h
View file

@ -37,11 +37,12 @@ typedef struct CoreCtx {
bool executedFunctionSync; // @0x3C
// Timer stuff
u64 emulPtimerOffsetThen; // @0x40. When setting cntp_cval_el0 and on interrupt
u64 totalTimeInHypervisor; // @0x40. cntvoff_el2 is updated to that value.
u64 emulPtimerOffsetThen; // @0x48. When setting cntp_cval_el0 and on interrupt
} CoreCtx;
static_assert(offsetof(CoreCtx, executedFunctionSync) == 0x3C, "Wrong definition for CoreCtx");
static_assert(offsetof(CoreCtx, emulPtimerOffsetThen) == 0x40, "Wrong definition for CoreCtx");
static_assert(offsetof(CoreCtx, emulPtimerOffsetThen) == 0x48, "Wrong definition for CoreCtx");
extern CoreCtx g_coreCtxs[4];
register CoreCtx *currentCoreCtx asm("x18");

54
thermosphere/src/exception_vectors.s
View file

@ -6,6 +6,8 @@
*/
#define STACK_FRAME_SIZE 0x140
/*
* Declare the exception vector table, enforcing it is aligned on a
* 2KB boundary, as required by the ARMv8 architecture.
@ -50,9 +52,14 @@
.endif
.endm
.macro SAVE_ALL_REGISTERS
stp x30, xzr, [sp, #-0x130]
bl _saveAllRegisters
.macro SAVE_MOST_REGISTERS
sub sp, sp, #STACK_FRAME_SIZE
stp x28, x29, [sp, #-0x20]
stp x30, xzr, [sp, #-0x10]
mrs x28, far_el2
mrs x29, cntpct_el0
bl _saveMostRegisters
.endm
.macro PIVOT_STACK_FOR_CRASH
@ -76,15 +83,23 @@ vector_entry \name
PIVOT_STACK_FOR_CRASH
.endif
SAVE_ALL_REGISTERS
SAVE_MOST_REGISTERS
.if \type == EXCEPTION_TYPE_GUEST
ldp x18, xzr, [sp, #0x120]
ldp x18, xzr, [sp, #STACK_FRAME_SIZE]
mov w1, #1
.else
mov w1, #0
.endif
mov x0, sp
bl exceptionEntryPostprocess
.endm
.macro EXCEPTION_HANDLER_END name, type
.if \type != EXCEPTION_TYPE_HOST_CRASH
mov x0, sp
bl exceptionReturnPreprocess
b _restoreAllRegisters
.else
b .
@ -117,8 +132,7 @@ _unknownException:
UNKNOWN_EXCEPTION _irqSp0
/* To save space, insert in an unused vector segment. */
_saveAllRegisters:
sub sp, sp, #0x120
_saveMostRegisters:
stp x0, x1, [sp, #0x00]
stp x2, x3, [sp, #0x10]
stp x4, x5, [sp, #0x20]
@ -133,22 +147,23 @@ _saveAllRegisters:
stp x22, x23, [sp, #0xB0]
stp x24, x25, [sp, #0xC0]
stp x26, x27, [sp, #0xD0]
stp x28, x29, [sp, #0xE0]
mov x29, x30
ldp x30, xzr, [sp, #-0x10] // See SAVE_ALL_REGISTERS macro
mrs x20, sp_el1
mrs x21, sp_el0
mrs x22, elr_el2
mrs x23, spsr_el2
mrs x24, cntvct_el0
mov x24, x28 // far_el2
mov x25, x29 // cntpct_el0
stp x30, x20, [sp, #0xF0]
// See SAVE_MOST_REGISTERS macro
ldp x28, x29, [sp, #-0x20]
ldp x19, xzr, [sp, #-0x10]
stp x28, x29, [sp, #0xE0]
stp x19, x20, [sp, #0xF0]
stp x21, x22, [sp, #0x100]
stp x23, x24, [sp, #0x110]
mov x30, x29
stp x25, xzr, [sp, #0x120]
ret
@ -162,18 +177,13 @@ UNKNOWN_EXCEPTION _fiqSp0
_restoreAllRegisters:
ldp x30, x20, [sp, #0xF0]
ldp x21, x22, [sp, #0x100]
ldp x23, x24, [sp, #0x110]
ldp x23, xzr, [sp, #0x110]
msr sp_el1, x20
msr sp_el0, x21
msr elr_el2, x22
msr spsr_el2, x23
// Update timer offset: offset = ptimer - vtimer; here the time elapsed is vct(now) - vct(before)
mrs x23, cntvct_el0
sub x24, x23, x24
msr cntvoff_el2, x24
ldp x0, x1, [sp, #0x00]
ldp x2, x3, [sp, #0x10]
ldp x4, x5, [sp, #0x20]
@ -190,7 +200,7 @@ _restoreAllRegisters:
ldp x26, x27, [sp, #0xD0]
ldp x28, x29, [sp, #0xE0]
add sp, sp, #0x120
add sp, sp, #STACK_FRAME_SIZE
eret
UNKNOWN_EXCEPTION _serrorSp0

35
thermosphere/src/exceptions.c
View file

@ -24,7 +24,7 @@
#include "single_step.h"
#include "data_abort.h"
#include "debug_log.h"
#include "timer.h"
bool spsrEvaluateConditionCode(u64 spsr, u32 conditionCode)
{
@ -60,13 +60,16 @@ void dumpStackFrame(const ExceptionStackFrame *frame, bool sameEl)
DEBUG("x30\t\t%016llx\n\n", frame->x[30]);
DEBUG("elr_el2\t\t%016llx\n", frame->elr_el2);
DEBUG("spsr_el2\t%016llx\n", frame->spsr_el2);
DEBUG("far_el2\t%016llx\n", frame->far_el2);
if (sameEl) {
DEBUG("sp_el2\t\t%016llx\n", frame->sp_el2);
} else {
DEBUG("sp_el0\t\t%016llx\n", frame->sp_el0);
}
DEBUG("sp_el1\t\t%016llx\n", frame->sp_el1);
DEBUG("cntvct_el0\t\t%016llx\n", frame->cntvct_el0);
DEBUG("cntpct_el0\t%016llx\n", frame->cntpct_el0);
DEBUG("cntp_ctl_el0\t%016llx\n", frame->cntp_ctl_el0);
DEBUG("cntv_ctl_el0\t%016llx\n", frame->cntv_ctl_el0);
#else
(void)frame;
(void)sameEl;
@ -92,6 +95,34 @@ void skipFaultingInstruction(ExceptionStackFrame *frame, u32 size)
frame->elr_el2 += size;
}
void exceptionEnterInterruptibleHypervisorCode(ExceptionStackFrame *frame)
{
(void)frame;
// We don't want the guest to spam us with its timer interrupts. Disable the timers.
SET_SYSREG(cntp_ctl_el0, 0);
SET_SYSREG(cntv_ctl_el0, 0);
}
// Called on exception entry (avoids overflowing a vector section)
void exceptionEntryPostprocess(ExceptionStackFrame *frame, bool isLowerEl)
{
frame->cntp_ctl_el0 = GET_SYSREG(cntp_ctl_el0);
frame->cntv_ctl_el0 = GET_SYSREG(cntv_ctl_el0);
}
// Called on exception return (avoids overflowing a vector section)
void exceptionReturnPreprocess(ExceptionStackFrame *frame)
{
// Update virtual counter
currentCoreCtx->totalTimeInHypervisor += timerGetSystemTick() - frame->cntpct_el0;
SET_SYSREG(cntvoff_el2, currentCoreCtx->totalTimeInHypervisor);
//DEBUG("pct %lu - vct %lu = voff %lu\n", timerGetSystemTick() - GET_SYSREG(cntvct_el0), GET_SYSREG(cntvoff_el2));
// Restore interrupt mask
SET_SYSREG(cntp_ctl_el0, frame->cntp_ctl_el0);
SET_SYSREG(cntv_ctl_el0, frame->cntv_ctl_el0);
}
void handleLowerElSyncException(ExceptionStackFrame *frame, ExceptionSyndromeRegister esr)
{
switch (esr.ec) {

11
thermosphere/src/exceptions.h
View file

@ -15,6 +15,7 @@
*/
#pragma once
#include <assert.h>
#include "utils.h"
typedef struct ExceptionStackFrame {
@ -26,9 +27,15 @@ typedef struct ExceptionStackFrame {
};
u64 elr_el2;
u64 spsr_el2;
u64 cntvct_el0;
u64 far_el2;
u64 cntpct_el0;
u64 cntp_ctl_el0;
u64 cntv_ctl_el0;
u64 reserved;
} ExceptionStackFrame;
static_assert(sizeof(ExceptionStackFrame) == 0x140, "Wrong size for ExceptionStackFrame");
// Adapted from https://developer.arm.com/docs/ddi0596/a/a64-shared-pseudocode-functions/shared-exceptions-pseudocode
typedef enum ExceptionClass {
Exception_Uncategorized = 0x0,
@ -130,6 +137,8 @@ bool spsrEvaluateConditionCode(u64 spsr, u32 conditionCode);
void skipFaultingInstruction(ExceptionStackFrame *frame, u32 size);
void dumpStackFrame(const ExceptionStackFrame *frame, bool sameEl);
void exceptionEnterInterruptibleHypervisorCode(ExceptionStackFrame *frame);
void handleLowerElSyncException(ExceptionStackFrame *frame, ExceptionSyndromeRegister esr);
void handleSameElSyncException(ExceptionStackFrame *frame, ExceptionSyndromeRegister esr);
void handleUnknownException(u32 offset);

5
thermosphere/src/initSystem.c
View file

@ -36,7 +36,12 @@ static void initSysregs(void)
SET_SYSREG(mdcr_el2, 0x00000000);
SET_SYSREG(mdscr_el1, 0x00000000);
// Timer stuff
SET_SYSREG(cntvoff_el2, 0x00000000);
SET_SYSREG(cnthctl_el2, 0x00000003); // Don't trap anything for now; event streams disabled
SET_SYSREG(cntkctl_el1, 0x00000003); // Don't trap anything for now; event streams disabled
SET_SYSREG(cntp_ctl_el0, 0x00000000);
SET_SYSREG(cntv_ctl_el0, 0x00000000);
}
void initSystem(u32 coreId, bool isBootCore, u64 argument)

31
thermosphere/src/irq.c
View file

@ -103,7 +103,8 @@ static inline bool checkRescheduleEmulatedPtimer(ExceptionStackFrame *frame)
{
// Evaluate if the timer really has expired in the PoV of the guest kernel. If not, reschedule (add missed time delta) it & exit early
u64 cval = GET_SYSREG(cntp_cval_el0);
if (cval > frame->cntvct_el0) {
u64 vct = frame->cntpct_el0 - currentCoreCtx->totalTimeInHypervisor;
if (cval > vct) {
// It has not: reschedule the timer
u64 offsetNow = GET_SYSREG(cntvoff_el2);
SET_SYSREG(cntp_cval_el0, cval + (offsetNow - currentCoreCtx->emulPtimerOffsetThen));
@ -115,6 +116,26 @@ static inline bool checkRescheduleEmulatedPtimer(ExceptionStackFrame *frame)
return true;
}
static inline bool checkGuestTimerInterrupts(ExceptionStackFrame *frame, bool isLowerEl, u16 irqId)
{
if (irqId != TIMER_IRQID(NS_VIRT_TIMER) && irqId != TIMER_IRQID(NS_PHYS_TIMER)) {
return true;
}
// A thing that might have happened is losing the race vs disabling the guest interrupts
// Another thing is that the virtual timer might have fired before us updating voff when executing a top half?
if (!isLowerEl) {
return false;
} else if (irqId == TIMER_IRQID(NS_VIRT_TIMER)) {
u64 cval = GET_SYSREG(cntp_cval_el0);
u64 vct = frame->cntpct_el0 - currentCoreCtx->totalTimeInHypervisor;
return cval <= vct;
} else {
return checkRescheduleEmulatedPtimer(frame);
}
}
static void doConfigureInterrupt(u16 id, u8 prio, bool isLevelSensitive)
{
volatile ArmGicV2Distributor *gicd = g_irqManager.gic.gicd;
@ -186,7 +207,6 @@ bool irqIsGuest(u16 id)
void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
{
(void)isLowerEl;
(void)isA32;
volatile ArmGicV2Controller *gicc = g_irqManager.gic.gicc;
@ -195,13 +215,13 @@ void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
u32 irqId = iar & 0x3FF;
u32 srcCore = (iar >> 10) & 7;
//DEBUG("EL2 [core %d]: Received irq %x\n", (int)currentCoreCtx->coreId, irqId);
DEBUG("EL2 [core %d]: Received irq %x\n", (int)currentCoreCtx->coreId, irqId);
if (irqId == GIC_IRQID_SPURIOUS) {
// Spurious interrupt received
return;
} else if (irqId == GIC_IRQID_NS_PHYS_TIMER && !checkRescheduleEmulatedPtimer(frame)) {
// Deactivate the ptimer interrupt, return early
} else if (!checkGuestTimerInterrupts(frame, isLowerEl, irqId)) {
// Deactivate the interrupt, return early
gicc->eoir = iar;
gicc->dir = iar;
return;
@ -254,6 +274,7 @@ void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
// Bottom half part
if (transportIface != NULL) {
exceptionEnterInterruptibleHypervisorCode(frame);
unmaskIrq();
transportInterfaceIrqHandlerBottomHalf(transportIface);
}

41
thermosphere/src/main.c
View file

@ -38,13 +38,50 @@ static void loadKernelViaSemihosting(void)
currentCoreCtx->kernelEntrypoint = buf;
}
void thermosphereMain(ExceptionStackFrame *frame)
#include "platform/uart.h"
typedef struct TestCtx {
char buf[512+1];
} TestCtx;
static TestCtx g_testCtx;
size_t testReceiveCallback(TransportInterface *iface, void *p)
{
TestCtx *ctx = (TestCtx *)p;
return transportInterfaceReadDataUntil(iface, ctx->buf, 512, '\r');
}
void testProcessDataCallback(TransportInterface *iface, void *p, size_t sz)
{
(void)iface;
(void)sz;
TestCtx *ctx = (TestCtx *)p;
DEBUG("EL2 [core %u]: you typed: %s\n", currentCoreCtx->coreId, ctx->buf);
}
void test(void)
{
TransportInterface *iface = transportInterfaceCreate(
TRANSPORT_INTERFACE_TYPE_UART,
DEFAULT_UART,
DEFAULT_UART_FLAGS,
testReceiveCallback,
testProcessDataCallback,
&g_testCtx
);
transportInterfaceSetInterruptAffinity(iface, BIT(0));
}
void thermosphereMain(ExceptionStackFrame *frame, u64 pct)
{
initIrq();
if (currentCoreCtx->isBootCore) {
transportInterfaceInitLayer();
debugLogInit();
test();
DEBUG("EL2: core %u reached main first!\n", currentCoreCtx->coreId);
}
@ -75,5 +112,5 @@ void thermosphereMain(ExceptionStackFrame *frame)
frame->spsr_el2 = (0xF << 6) | (1 << 2) | 1; // EL1h+DAIF
frame->elr_el2 = currentCoreCtx->kernelEntrypoint;
frame->x[0] = currentCoreCtx->kernelArgument;
frame->cntvct_el0 = GET_SYSREG(cntvct_el0);
frame->cntpct_el0 = pct;
}

5
thermosphere/src/start.s
View file

@ -39,6 +39,8 @@ _startCommon:
msr daifset, 0b1111
msr spsel, #1
mrs x20, cntpct_el0
// Set sctlr_el2 ASAP to disable mmu/caching if not already done.
mov x1, #0x0838
movk x1, #0x30C5,lsl #16
@ -69,12 +71,13 @@ _startCommon:
// Save x18, reserve space for exception frame
stp x18, xzr, [sp, #-0x10]!
sub sp, sp, #0x120
sub sp, sp, #0x140
dsb sy
isb
mov x0, sp
mov x1, x20
bl thermosphereMain
dsb sy

11
thermosphere/src/sysreg_traps.c
View file

@ -27,11 +27,13 @@ static inline u64 doSystemRegisterRead(const ExceptionStackFrame *frame, u32 nor
u64 val;
switch (normalizedIss) {
case ENCODE_SYSREG_ISS(CNTPCT_EL0): {
val = frame->cntvct_el0;
u64 vct = frame->cntpct_el0 - currentCoreCtx->totalTimeInHypervisor;
val = vct;
break;
}
case ENCODE_SYSREG_ISS(CNTP_TVAL_EL0): {
val = (GET_SYSREG(cntp_cval_el0) - frame->cntvct_el0) & 0xFFFFFFFF;
u64 vct = frame->cntpct_el0 - currentCoreCtx->totalTimeInHypervisor;
val = (GET_SYSREG(cntp_cval_el0) - vct) & 0xFFFFFFFF;
break;
}
case ENCODE_SYSREG_ISS(CNTP_CTL_EL0): {
@ -58,7 +60,7 @@ static inline u64 doSystemRegisterRead(const ExceptionStackFrame *frame, u32 nor
static inline void writeEmulatedPhysicalCompareValue(u64 val)
{
currentCoreCtx->emulPtimerOffsetThen = GET_SYSREG(cntvoff_el2);
currentCoreCtx->emulPtimerOffsetThen = currentCoreCtx->totalTimeInHypervisor;
SET_SYSREG(cntp_cval_el0, val);
}
@ -69,7 +71,8 @@ static inline void doSystemRegisterWrite(const ExceptionStackFrame *frame, u32 n
switch (normalizedIss) {
case ENCODE_SYSREG_ISS(CNTP_TVAL_EL0): {
// Sign-extend
writeEmulatedPhysicalCompareValue(frame->cntvct_el0 + (u64)(s32)val);
u64 vct = frame->cntpct_el0 - currentCoreCtx->totalTimeInHypervisor;
writeEmulatedPhysicalCompareValue(vct + (u64)(s32)val);
break;
}
case ENCODE_SYSREG_ISS(CNTP_CTL_EL0): {

6
thermosphere/src/timer.c
View file

@ -21,7 +21,7 @@ u64 g_timerFreq = 0;
void timerInit(void)
{
timerSetInterruptStatus(false, false);
timerConfigure(false, false);
if (currentCoreCtx->isBootCore) {
g_timerFreq = GET_SYSREG(cntfrq_el0);
}
@ -29,8 +29,8 @@ void timerInit(void)
void timerInterruptHandler(void)
{
// Disable timer interrupts until reprogrammed
timerSetInterruptStatus(false, false);
// Disable timer programming until reprogrammed
timerConfigure(false, false);
// For fun
DEBUG("EL2 [core %d]: Timer interrupt at %lums\n", (int)currentCoreCtx->coreId, timerGetSystemTimeMs());

13
thermosphere/src/timer.h
View file

@ -45,6 +45,10 @@
#define TIMER_CVAL_REG(name) EVAL(TIMER_CVAL_REG_FIELDS name)
#define TIMER_TVAL_REG(name) EVAL(TIMER_TVAL_REG_FIELDS name)
#define TIMER_CTL_ISTATUS BITL(2)
#define TIMER_CTL_IMASK BITL(1)
#define TIMER_CTL_ENABLE BITL(0)
#define CURRENT_TIMER NS_PHYS_HYP_TIMER
extern u64 g_timerFreq;
@ -67,17 +71,18 @@ static inline u64 timerGetSystemTimeMs(void)
return timerGetSystemTick() * SECTOMSECS / g_timerFreq;
}
static inline void timerSetInterruptStatus(bool enabled, bool masked)
static inline void timerConfigure(bool enabled, bool interruptMasked)
{
u32 ebit = enabled ? BIT(0) : 0;
u32 mbit = masked ? BIT(1) : 0;
u64 ebit = enabled ? TIMER_CTL_ENABLE : 0;
u64 mbit = interruptMasked ? TIMER_CTL_IMASK : 0;
SET_SYSREG(TIMER_CTL_REG(CURRENT_TIMER), mbit | ebit);
}
static inline void timerSetTimeoutTicks(u64 ticks)
{
timerConfigure(true, true);
SET_SYSREG(TIMER_CVAL_REG(CURRENT_TIMER), timerGetSystemTick() + ticks);
timerSetInterruptStatus(true, false);
timerConfigure(true, false);
}
static inline void timerSetTimeoutNs(u64 ns)