130 lines
4.4 KiB
C
130 lines
4.4 KiB
C
//---
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// fxcg50:initialize - Kernel initialization and C runtime
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//---
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#include "vhex/hardware.h"
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#include "vhex/kernel.h"
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#include <stdint.h>
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#include <stdlib.h>
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#include <setjmp.h>
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/* Constructor and destructor arrays */
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extern void (*bctors)(void), (*ectors)(void);
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extern void (*bdtors)(void), (*edtors)(void);
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/* User-provided main() function */
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extern int main(void);
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/* Jumping there will properly unwind and leave the kernel */
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jmp_buf vhex_exitbuf;
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/* Return value of main() */
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int vhex_exitcode;
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/* callarray(): Call an array of functions (constructors or destructors) */
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static void callarray(void (**f)(void), void (**l)(void))
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{
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while(f < l) (*(*f++))();
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}
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/* initialize() : Where it all starts
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We are currently in a RAM location at a non-constant address due to the
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relocalization performed by the bootloader. Moreover, we are in privileged
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mode with one golden rule:
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Do not disturb the operating system
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Why we should keep this rule in mind? Because, on this particular device,
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none of all hardware and software information are documented. Vhex will
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therefore involve Casio's syscall to perform some interaction, especially
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concerning file manipulation.
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Note that we don't need to change the stack, the kernel will use the one
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given by Casio because it's big enough to store the user-application
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(mainly the vxOS) and the kernel code. However, we need to keep in mind
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that for this device, a lot of hardware supposition will be performed here,
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chiefly concerning the memory discovery.
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+---------------+
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| Reserved Area |
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+ - - - - - - - + <-- virtually mapped at 0x0810000
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| _vxKernel |
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| + |
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| _vxOS |
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+ - - - - - - - + <-- Provided by the vxKernel (variable)
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| Stack |
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+ - - - - - - - + <-- end of the TLB information (variable)
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| kmalloc() |
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+---------------+ <-- variable
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We know that the "user RAM" is *constantly* mapped at 0x08100000 and all the
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memory reserved for the user is completely loaded and all of this information
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is stored at the end of the UTLB. Moreover, the stack provided by Casio start
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at the end of the "user RAM". So, the memory layout is a bit exotic and look
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like above. */
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void initialize(void)
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{
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/* Detect hardware information : This part is important because it will
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tell us if we are running in an emulator or on a real device. */
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hw_detect();
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/* Install Vhex, switch VBR and initialize drivers */
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kinit();
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//TODO: add area for the kmalloc() ?
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/* We are now running on our own in kernel mode. Since we have taken
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control of interrupts, pretty much any interaction with the system
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will break it. We'll limit our use of syscalls and do device driving
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ourselves. (Hopefully we can add cool features in the process!) */
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/* Now that we have initialized the kernel, we are ready to start the
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hosted user application, which has its own constructors and
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destructors to work with. */
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/* Here, we use exit() to allow the standard library to do
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what it wants in exit() after main() finishes executing */
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if(!setjmp(vhex_exitbuf)) {
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callarray(&bctors, &ectors);
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exit(main());
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}
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else {
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callarray(&bdtors, &edtors);
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}
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/* Before leaving the kernel (which will return to the bootloader menu),
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we need to clean everything we changed to hardware settings and
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peripheral modules. The OS is bound to be confused (and hang, or
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crash, or any other kind of giving up) if we don't restore them. */
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/* Unload vhex and give back control to the system. Driver settings
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will be restored while interrupts are disabled */
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kquit();
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//TODO: involve manualy the Casio's OS-menu
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}
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