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move GOOS=tamago MMU initialization and exception handling to linked …
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…application
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@abarisani
abarisani committed Apr 12, 2021
1 parent f419902 commit cabc6f7
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Showing 2 changed files with 97 additions and 418 deletions.
288 changes: 35 additions & 253 deletions src/runtime/os_tamago_arm.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,55 +10,8 @@ import (
"unsafe"
)

const tamagoDebug = true

const _PAGESIZE uintptr = 0x1000

// ARM processor modes
// Table B1-1 ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition
const (
USR_MODE = 0b10000
FIQ_MODE = 0b10001
IRQ_MODE = 0b10010
SVC_MODE = 0b10011
MON_MODE = 0b10110
ABT_MODE = 0b10111
HYP_MODE = 0b11010
UND_MODE = 0b11011
SYS_MODE = 0b11111
)

// Memory region attributes
// Table B3-10 ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition
const (
TTE_SECTION_1MB uint32 = 0x2
TTE_SECTION_16MB uint32 = 0x40002
TTE_EXECUTE_NEVER uint32 = 0x10
TTE_CACHEABLE uint32 = 0x8
TTE_BUFFERABLE uint32 = 0x4
)

// MMU access permissions
// Table B3-8 ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition
const (
// PL1: no access PL0: no access
TTE_AP_000 uint32 = 0b000000 << 10
// PL1: read/write PL0: no access
TTE_AP_001 uint32 = 0b000001 << 10
// PL1: read/write PL0: read only
TTE_AP_010 uint32 = 0b000010 << 10
// PL1: read/write PL0: read/write
TTE_AP_011 uint32 = 0b000011 << 10
// Reserved
TTE_AP_100 uint32 = 0b100000 << 10
// PL1: read only PL0: no access
TTE_AP_101 uint32 = 0b100001 << 10
// PL1: read only PL0: read only
TTE_AP_110 uint32 = 0b100010 << 10
// PL1: read only PL0: read only
TTE_AP_111 uint32 = 0b100011 << 10
)

// the following variables must be provided externally
var ramStart uint32
var ramStackOffset uint32
Expand All @@ -70,83 +23,53 @@ var ramStackOffset uint32
// the following functions must be provided externally
func hwinit()
func printk(byte)
func exceptionHandler()
func getRandomData([]byte)
func initRNG()

// the following functions must be provided externally
// (but are already stubbed somewhere else in the runtime)
//func nanotime1() int64

// the following functions are defined in sys_tamago_arm.s
func set_vbar(addr unsafe.Pointer)
func set_ttbr0(addr unsafe.Pointer)
func set_exc_stack(addr unsafe.Pointer)
func processor_mode() uint32
// GetRandomData generates len(r) random bytes from the random source provided
// externally by the linked application.
func GetRandomData(r []byte) {
getRandomData(r)
}

// CallOnG0 calls a function (func(off int)) on g0 stack.
//
// The function arguments must be passed through the following registers
// (rather than on the frame pointer):
//
// * R0: fn argument (vector table offset)
// * R1: fn pointer
// * R2: size of stack area reserved for caller registers
// * R3: caller program counter
func CallOnG0()

//go:nosplit
func dmb()
// MemRegion returns the start and end addresses of the physical RAM assigned
// to the Go runtime.
func MemRegion() (start uint32, end uint32) {
return ramStart, ramStart + ramSize
}

// stubs for unused/unimplemented functionality
type mOS struct{}
type sigset struct{}
type gsignalStack struct{}

func goenvs() {}
func sigsave(p *sigset) {}
func msigrestore(sigmask sigset) {}
func clearSignalHandlers() {}
func sigblock(exiting bool) {}
func minit() {}
func unminit() {}
func mdestroy(mp *m) {}
func madvise(addr unsafe.Pointer, n uintptr, flags int32) {}
func munmap(addr unsafe.Pointer, n uintptr) {}
func setProcessCPUProfiler(hz int32) {}
func setThreadCPUProfiler(hz int32) {}
func initsig(preinit bool) {}
func sigdisable(uint32) {}
func sigenable(uint32) {}
func sigignore(uint32) {}
func closeonexec(int32) {}
func osyield() {}

// global variables
var vt *vector_table

var vecTableOffset uint32 = 0
var vecTableSize uint32 = 0x4000 // 16 kB

var l1pageTableOffset uint32 = 0x4000 // 16 kB
var l1pageTableSize uint32 = 0x4000 // 16 kB

var excStackOffset uint32 = 0x8000 // 32 kB
var excStackSize uint32 = 0x4000 // 16 kB

// the following variables are set in sys_tamago_arm.s
var stackBottom uint32

// Table 11-1 ARM® Cortex™ -A Series Programmer’s Guide
type vector_table struct {
// jump entries
reset uint32
undefined uint32
svc uint32
prefetch_abort uint32
data_abort uint32
_unused uint32
irq uint32
fiq uint32
// call pointers
reset_addr uint32
undefined_addr uint32
svc_addr uint32
prefetch_abort_addr uint32
data_abort_addr uint32
_unused_addr uint32
irq_addr uint32
fiq_addr uint32
}
func goenvs() {}
func sigsave(p *sigset) {}
func msigrestore(sigmask sigset) {}
func clearSignalHandlers() {}
func sigblock(exiting bool) {}
func minit() {}
func unminit() {}
func mdestroy(mp *m) {}
func setProcessCPUProfiler(hz int32) {}
func setThreadCPUProfiler(hz int32) {}
func initsig(preinit bool) {}
func osyield() {}

// May run with m.p==nil, so write barriers are not allowed.
//go:nowritebarrier
Expand Down Expand Up @@ -177,10 +100,7 @@ func osinit() {
}

func signame(sig uint32) string {
if sig >= uint32(len(sigtable)) {
return ""
}
return sigtable[sig].name
return ""
}

func checkgoarm() {
Expand Down Expand Up @@ -212,142 +132,6 @@ func crash() {
*(*int32)(nil) = 0
}

func GetRandomData(r []byte) {
getRandomData(r)
}

// the following functions are defined in sys_tamago_arm.s
func resetHandler()
func undefinedHandler()
func svcHandler()
func prefetchAbortHandler()
func dataAbortHandler()
func irqHandler()
func fiqHandler()

func fnAddress(fn func()) uint32 {
return **((**uint32)(unsafe.Pointer(&fn)))
}

//go:nosplit
func vecinit() {
if processor_mode() != SYS_MODE {
return
}

// Allocate the vector table
vecTableStart := ramStart + vecTableOffset
memclrNoHeapPointers(unsafe.Pointer(uintptr(vecTableStart)), uintptr(vecTableSize))
dmb()

// ldr pc, [pc, #24]
resetVectorWord := uint32(0xe59ff018)

vt = (*vector_table)(unsafe.Pointer(uintptr(vecTableStart)))
vt.reset = resetVectorWord
vt.undefined = resetVectorWord
vt.svc = resetVectorWord
vt.prefetch_abort = resetVectorWord
vt.data_abort = resetVectorWord
vt._unused = resetVectorWord
vt.irq = resetVectorWord
vt.fiq = resetVectorWord

vt.reset_addr = fnAddress(resetHandler)
vt.undefined_addr = fnAddress(undefinedHandler)
vt.svc_addr = fnAddress(svcHandler)
vt.prefetch_abort_addr = fnAddress(prefetchAbortHandler)
vt.data_abort_addr = fnAddress(dataAbortHandler)
vt.irq_addr = fnAddress(irqHandler)
vt.fiq_addr = fnAddress(fiqHandler)

set_vbar(unsafe.Pointer(vt))

// Allocate stack pointer for exception modes to provide a stack to the
// g0 goroutine when summoned by exception vectors.
excStackStart := ramStart + excStackOffset
memclrNoHeapPointers(unsafe.Pointer(uintptr(excStackStart)), uintptr(excStackSize))
dmb()

set_exc_stack(unsafe.Pointer(uintptr(excStackStart + excStackSize)))

if !tamagoDebug {
return
}

print("vecTableStart ", hex(vecTableStart), "\n")
print("vecTableSize ", hex(vecTableSize), "\n")
print("excStackStart ", hex(excStackStart), "\n")
print("excStackSize ", hex(excStackSize), "\n")
print("stackBottom ", hex(stackBottom), "\n")
print("g0.stackguard0 ", hex(g0.stackguard0), "\n")
print("g0.stackguard1 ", hex(g0.stackguard1), "\n")
print("g0.stack.lo ", hex(g0.stack.lo), "\n")
print("g0.stack.hi ", hex(g0.stack.hi), "\n")
print("-- ELF image layout (firstmoduledata dump) --\n")
print(".text ", hex(firstmoduledata.text), " - ", hex(firstmoduledata.etext), "\n")
print(".noptrdata ", hex(firstmoduledata.noptrdata), " - ", hex(firstmoduledata.enoptrdata), "\n")
print(".data ", hex(firstmoduledata.data), " - ", hex(firstmoduledata.edata), "\n")
print(".bss ", hex(firstmoduledata.bss), " - ", hex(firstmoduledata.ebss), "\n")
print(".noptrbss ", hex(firstmoduledata.noptrbss), " - ", hex(firstmoduledata.enoptrbss), "\n")
print(".end ", hex(firstmoduledata.end), "\n")

imageSize := uint32(firstmoduledata.end - firstmoduledata.text)
heapSize := uint32(g0.stack.lo - firstmoduledata.end)
stackSize := uint32(g0.stack.hi - g0.stack.lo)
unusedSize := uint32(firstmoduledata.text) - (excStackStart + excStackSize) + ramStackOffset
totalSize := vecTableSize + l1pageTableSize + excStackSize + imageSize + heapSize + stackSize + unusedSize

print("-- Memory section sizes ---------------------\n")
print("vector table: ", vecTableSize, " (", vecTableSize/1024, " kB)\n")
print("L1 page table: ", l1pageTableSize, " (", l1pageTableSize/1024, " kB)\n")
print("exception stack: ", excStackSize, " (", excStackSize/1024, " kB)\n")
print("program image: ", imageSize, " (", imageSize/1024, " kB)\n")
print("heap: ", heapSize, " (", heapSize/1024, " kB)\n")
print("g0 stack: ", stackSize, " (", stackSize/1024, " kB)\n")
print("total unused: ", unusedSize, " (", unusedSize/1024, " kB)\n")
print("total: ", totalSize, " (", totalSize/1024, " kB)\n")
print("---------------------------------------------\n")
}

//go:nosplit
func mmuinit() {
// Initialize page tables and map regions in privileged system area.
//
// MMU initialization is required to take advantage of data cache.
//
// Define a flat L1 page table, the MMU is enabled only for caching to work.
// The L1 page table is located 16KB after ramStart.

if processor_mode() != SYS_MODE {
return
}

l1pageTableStart := ramStart + l1pageTableOffset
memclrNoHeapPointers(unsafe.Pointer(uintptr(l1pageTableStart)), uintptr(l1pageTableSize))

memAttr := uint32(TTE_AP_011 | TTE_CACHEABLE | TTE_BUFFERABLE | TTE_SECTION_1MB)
devAttr := uint32(TTE_AP_011 | TTE_SECTION_1MB)

// skip page zero to trap null pointers
for i := uint32(1); i < l1pageTableSize/4; i++ {
if i >= (ramStart>>20) && i < ((ramStart+ramSize)>>20) {
*(*uint32)(unsafe.Pointer(uintptr(l1pageTableStart + 4*i))) = (i << 20) | memAttr
} else {
*(*uint32)(unsafe.Pointer(uintptr(l1pageTableStart + 4*i))) = (i << 20) | devAttr
}
}

dmb()

if tamagoDebug {
print("l1pageTableStart ", hex(l1pageTableStart), "\n")
print("l1pageTableSize ", hex(l1pageTableSize), "\n")
}

set_ttbr0(unsafe.Pointer(uintptr(l1pageTableStart)))
}

//go:linkname syscall
func syscall(number, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
switch number {
Expand Down Expand Up @@ -416,7 +200,5 @@ func exitThread(wait *uint32) {
const preemptMSupported = false

func preemptM(mp *m) {
// Not currently supported.
//
// TODO: Use a note like we use signals on POSIX OSes
// No threads, so nothing to do.
}
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