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115 lines
4.0 KiB
C++
115 lines
4.0 KiB
C++
/*! \file
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* \brief Startup of additional cores, the application processors (APs)
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*/
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#pragma once
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#include "../compiler/fix.h"
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#include "../types.h"
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/*! \brief Application Processor Boot
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*
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* Interface to boot the APs
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*/
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namespace ApplicationProcessor {
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/*! \brief Address (below 1 MiB) to which the setup code gets relocated
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*/
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constexpr uintptr_t RELOCATED_SETUP = 0x40000;
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/*! \brief Relocate the real mode setup code
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*
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* The application processors (APs) start in real mode, which means that your
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* setup code must be placed within the first megabyte -- your operating system
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* resides currently at a much higher address (16 MiB), so the code has to be
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* copied down there first.
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*
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* Luckily, the code in `setup_ap()` can be relocated by copying -- because it
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* does not use any absolute addressing (except when jumping to the protected
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* mode function `startup_ap()`).
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* The function must be copied to the address of \ref RELOCATED_SETUP (0x40000),
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* so that the APs can start there.
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*
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* The memory section contains a reserved area for the \ref GDT and its
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* descriptor, which has to be assigned first with the contents of \ref ap_gdt.
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*
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* \note You could also tell the linker script to put the code directly
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* at the appropriate place, but unfortunately the Qemu multiboot
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* implementation (via `-kernel` parameter) can't handle it properly.
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*/
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void relocateSetupCode();
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/*! \brief Boot all application processors
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*
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* Performs relocation by calling \ref relocateSetupCode()
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*
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* \see [ISDMv3, 8.4.4.2 Typical AP Initialization
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* Sequence](intel_manual_vol3.pdf#page=276)
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*/
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void boot();
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} // namespace ApplicationProcessor
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/*! \brief Begin of setup code for application processors
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*
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* The setup code has to switch from real mode (16 bit) to protected mode (32
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* bit), hence it is written in assembly and must be executed in low memory (< 1
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* MiB).
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*
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* After kernel start the code is somewhere above 16 MiB (the bootstrap
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* processor was already launched in protected mode by the boot loader).
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* Therefore this symbol is required for relocate the code to the position
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* specified by \ref ApplicationProcessor::RELOCATED_SETUP.
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*
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* Luckily, the `setup_ap` code in `boot/startup_ap.asm` is rather simple and
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* doesn't depend on absolute addressing -- and is therefore relocatable.
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*
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* Relocation is done by the function \ref
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* ApplicationProcessor::relocateSetupCode()
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*
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* The `___SETUP_AP_START__` symbol is defined in the linker script
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* (`compiler/section.ld`)
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*/
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extern char ___SETUP_AP_START__;
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/*! \brief End of startup code for application processors
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*
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* This Symbol is defined in the linker script (`compiler/section.ld`)
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*/
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extern char ___SETUP_AP_END__;
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/*! \brief Memory reserved for a temporary real mode GDT
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* within the relocatable memory area of the setup code
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*/
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extern char setup_ap_gdt;
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/*! \brief Memory reserved for a temporary real mode GDT descriptor
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* within the relocatable memory area of the setup code
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*/
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extern char setup_ap_gdtd;
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/*! \brief Entry point for application processors
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*
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* Unlike the bootstrap processor, the application processors have not been
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* setup by the boot loader -- they start in `Real Mode` (16 bit) and have to be
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* switched manually to `Protected Mode` (32 bit).
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* This is exactly what this real mode function does, handing over control
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* to the (32 bit) function \ref startup_ap()
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*
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* This code is written is assembly (`boot/startup_ap.asm`) and relocated by
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* \ref ApplicationProcessor::relocateSetupCode() during
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* \ref ApplicationProcessor::boot()
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*/
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extern "C" void setup_ap() ERROR_ON_CALL(
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"The setup function for application processors shall never be called from "
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"your code!");
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/*! \brief Startup for application processors
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* \ingroup Startup
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*
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* This function behaves similar to \ref startup_bsp():
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* Initializes stack pointer,
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* switches to long mode
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* and calls the C++ \ref kernel_init function
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*/
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extern "C" void startup_ap() ERROR_ON_CALL(
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"The startup function for application processors shall never be called "
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"from your code!");
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