kernel.c

#include "addrs.h"
#include "elf.h"
#include "htif.h"
#include "util.h"

// Include the ELF contents of relocatable apps for us to load.
// All of these apps need to be compiled with -fepic.

// Example app: CoreMark.
__attribute__ ((aligned(8))) const
#include "cm.h"

int main() {
    // Arbitrary SRAM and Flash app relocation offsets.
    // You can change these to relocate the loadable app. Just be sure you
    // don't collide with the kernel (0x80000000-~0x80010000) and that the
    // address range has been made available in spike. The first two pages
    // (0 - 0x2000) are reserved by spike and the third page contains the
    // host-target interface symbols defined in the kernel (0x2000, 0x2008).
    size_t sram_offset = 0x12340000;
    size_t flash_offset = 0x2345000;

    const void* elf_data = cm; // App to load.

    // Simulate programming "Flash" with an app's ELF file contents.
    size_t entry = program_flash_with_elf(elf_data, flash_offset);
    if (entry == 0) {
        print("Failed to load app\n");
        return 1;
    }

    // Set the GP register (the PIC base) to the app's SRAM base address.
    // This is needed every time control is transfered to a different
    // relocatable app.
    asm volatile("mv gp, %0" :: "r"(sram_offset));

    // Transfer control to the app we loaded.
    size_t app_start = FLASH_MEM_START + flash_offset;
    ((int(*)(size_t, size_t, size_t))entry)(app_start, flash_offset, sram_offset);

    return 0;
}