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`if NCPUS > 1` stuff is not being considered so far.

grub starts the execution at boot\_entry

> i386/i386at/boothdr.S: boot\_entry: sets up C environment, i.e. sets up a basic stack and clears BSS, fixes ifunc.

> i386/i386at/model\_dep.c: c\_boot\_entry: gets multiboot parameters

>> i386/i386at/boothdr.S: discover\_x86\_cpu\_type: detect processor type

>> i386/i386at/model\_dep.c: i386at\_init: initialize PC-specific stuff

>>> i386/i386/pic.c: picinit: initialize 8259 PIC

>>> i386/i386at/model\_dep.c: mem\_size\_init: compute memory size

>>> i386/intel/pmap.c: pmap\_bootstrap: initialize x86 page table

>>> i386/i386/gdt.c: gdt\_init: initialize x86 segmentation

>>> i386/i386/idt.c: idt\_init: initialize x86 traps

>>> i386/i386at/int\_init.c: int\_init: initialize PC interrupts

>>> i386/i386/ldt.c: ldt\_init: initialize x86 segmentation

>>> i386/i386/ktss.c: ktss\_init: initialize x86 task switching

>> kern/startup.c: setup\_main: set up non-hardware specific stuff

>>> kern/debug.c: panic\_init: initialize panic data

>>> kern/printf.c: printf\_init: initialize printf

>>> kern/sched\_prim.c: sched\_init: initialize scheduler

>>>> kern/processor.c: pset\_sys\_bootstrap: initialize processor sets

>>>> kern/ast.c: ast\_init: initialize Asychronous System Traps

>>> vm/vm\_init.c: vm\_mem\_bootstrap: initialize virtual memory

>>>> vm/vm\_resident.c: vm\_page\_bootstrap: turn physical pages into virtually allocatable pages

>>>>> vm/vm\_resident.c: pmap\_startup: initialize pages

>>>> kern/slab.c: slab\_bootstrap: early-initialize SLAB

>>>> vm/vm\_object.c: vm\_object\_bootstrap: initialize VM object management

>>>>> vm/vm\_external.c: vm\_external\_module\_initialize: initialize VM external object management

>>>> vm/vm\_map.c: vm\_map\_init: initialize VM maps

>>>> vm/vm\_kern.c: kmem\_init: initialize kernel's virtual memory

>>>> i386/intel/pmap.c: pmap\_init: initialize remainder of x86 page table

>>>> kern/slab.c: slab\_init: initialize remainder of SLAB

>>>> kern/kalloc.c: kalloc\_init: initialize kallocator

>>>> vm/vm\_fault.c: vm\_fault\_init: initialize VM fault management

>>>> vm/vm\_resident.c: vm\_page\_module\_init: initialize remainder of virtual memory

>>>> vm/memory\_object.c: memory\_manager\_default\_init: initialize remainder of VM object management

>>> ipc/ipc\_init.c: ipc\_bootstrap: initialize IPC

>>>> ipc/ipc\_table.c: ipc\_table\_init: initialize IPC tables

>>>> ipc/ipc\_notify.c: ipc\_notify\_init: initialize IPC notification

>>>> ipc/ipc\_hash.c: ipc\_hash\_init: initialize IPC reverse hash table

>>>> ipc/ipc\_marequest.c: ipc\_marequest\_init: initialize msg-accepted request

>>> vm/vm\_init.c: vm\_mem\_init: finish initializing VM

>>>> vm/vm\_object.c: vm\_object\_init: finish initializing kernel object

>>>> vm/memory\_object\_proxy: memory\_object\_proxy\_init: initialize memory object proxy

>>> ipc/ipc\_init.c: ipc\_init: finish initializing IPC

>>>> kern/ipc\_host.c: ipc\_host\_init: initialize host IPC

>>>>> kern/ipc\_host.c: ipc\_pset\_init: initialize processor sets ports

>>>>> kern/ipc\_host.c: ipc\_processor\_init: initialize processor ports

>>> i386/intel/pmap.h: PMAP\_ACTIVATE\_KERNEL: activate kernel page table

>>> kern/timer.c: init\_timers: initialize timers

>>> kern/mach\_clock.c: init\_timeout: initialize timeout

>>> kern/xpr.c: xprbootstrap: initialize xpr buffer

>>> kern/time\_stamp.c: timestamp\_init: initialize tick

>>> kern/mach\_clock.c: [[mapable\_time\_init|interface/device/time]]

>>> i386/i386at/model\_dep.c: machine\_init: initialize x86 machine

>>>> device/cons.c: cninit: initialize console

>>>> i386/i386/fpu.c: init\_fpu: initialize 8087 FPU

>>>> linux/dev/init/main.c: linux\_init: initialize linux drivers

>>>>> linux/dev/arch/i386/kernel/irq.c: init\_IRQ: initialize IRQs

>>>>>> linux/dev/arch/i386/kernel/irq.c: reserve\_mach\_irqs: register IRQs to mach

>>>>> linux/dev/kernel/sched.c: linux\_sched\_init: initialize dumb scheduler

>>>>> linux/dev/init/main.c: calibrate\_delay: calibrate delay loop

>>>>> linux/dev/glue/kmem.c: linux\_kmem\_init: initialize memory management

>>>>> linux/src/drivers/pci/pci.c: pci\_init: initialize PCI bus

>>>>>> linux/src/arch/i386/kernel/bios32.c: pcibios\_init: call PCI BIOS32 initialization

>>>>>> linux/src/drivers/pci/pci.c: scan\_bus: enumerate PCI devices

>>>>>> linux/src/arch/i386/kernel/bios32.c: pcibios\_fixup: apply platform-specific fixes

>>>>> linux/dev/glue/net.c: linux\_net\_emulation\_init: initialize network glue

>>>>> linux/dev/drivers/block/genhd.c: device\_setup: initialize block devices

>>>>>> linux/dev/glue/block.c: blk\_dev\_init: initialize linux block devices

>>>>>>> linux/src/drivers/block/ide.c: ide\_init: initialize IDE driver

>>>>>>> linux/dev/drivers/block/floppy.c: floppy\_init: initialize floppy driver

>>>>>> linux/src/drivers/scsi/scsi.c: scsi\_dev\_init: initialize SCSI drivers

>>>>>> linux/dev/net/core/dev.c: net\_dev\_init: initialize network drivers

>>>>> linux/pcmcia-cs/glue/pcmcia.c: pcmcia\_init: initialize PCMCIA drivers

>>>> i386/i386at/autoconf.c: probeio: probe mach-managed devices (com, lpr)

>>>> i386/i386at/model\_dep.c: inittodr: get RTC time

>>>> i386/intel/pmap.c: pmap\_unmap\_page\_zero: unmap address 0

>>>> kern/mach\_clock.c: mapable\_time\_init: initialize mappable time

>>> kern/task.c: task\_init: initialize gnuamch atsk

>>>> kern/syscall\_emulation.c: eml\_init: initialize user space emulation code

>>> kern/thread.c: thread\_init: initialize thread management

>>>> i386/i386/pcb.c: pcb\_module\_init: initialize PCB management

>>>>> i386/i386/fpu.c: fpu\_module\_init: initialize FPU management

>>> kern/thread\_swap.c: swapper\_init: initialize thread swapper

>>> kern/sched\_prim.c: recompute\_priorities: initial priorities computation

>>> kern/mach\_factor.c: compute\_mach\_factor: initial mach factor computation

>>> kern/startup.c: thread\_start: create initial kernel thread

>>> kern/startup.c: cpu\_launch\_first\_thread: start first user thread

>>>> i386/intel/pmap.h: PMAP\_ACTIVATE\_KERNEL: activate kernel page table

>>>> i386/i386at/model\_dep.c: startrtclock: start clock

>>>>> i386/i386/pit.c: clkstart: start 8254 PIT

>>>> i386/intel/pmap.h: PMAP\_ACTIVATE\_KERNEL: activate user page table

>>>> i386/i386/pcb.c: load\_context: load first context

[...]

> kern/startup.c: start\_kernel\_threads

> Threads get created.

>> kern/sched\_prim.c: idle\_thread

>> One for each CPU.

>> kern/thread.c: reaper\_thread 

>> kern/thread\_swap.c: swapin\_thread

>> kern/sched\_prim.c: sched\_thread

>> [...]

>> kern/bootstrap.c: bootstrap\_create

>>> The [[grub/multiboot]] modules have been put somewhere into memory by
>>> [[GRUB]].  The boot scripts are parsed.  The modules' ELF image's `PT_LOAD`
>>> sections are \`\`read'' (that is, `vm_allocate` and `copyout`) and turned
>>> into real [[task]]s.  The multiboot modules' memory regions can be
>>> deallocated then.

>> [...]

>> vm\_pageout: run the paging out daemon

>> Does not return.


# IRC, freenode, #hurd, 2013-10-07

    <cureOS> look, where should i dig or where from should i start from, if i
      have desire to know how the kernel was written from baremetal? Can it be
      ever done nowadays?
    <youpi> cureOS: the boot entry of the kernel is i386/i386at/boothdr.S ,
      boot_entry
    <youpi> that's what grub jumps to
    <youpi> then that jumps to c_boot_entry
    <youpi> and everything else is C
    <cureOS> grub loads it somehow. how does it prepare cpu and memoty, cpu
      cache control if any... segments for stack..
    <youpi> see the grub documentation
    <youpi> basically it's all flat linear space
    <cureOS> does kernel transform it after that?
    <youpi> see the ldt/gdt initialization
    <youpi> from i386at_init and children
    <youpi> nothing much fancy, a kernel cs/ds, and user cs/ds
    <braunr> and paging, naturally
    <youpi> sure