all_services.cpp

#include <string.h>
#include <stdlib.h>
#include <stdio.h>

#include <3ds.h>

static const u32 KPROC_OFFSET_PID = 0xB4;

static u32 self_pid;
static u32 curr_kproc;

int __attribute__((naked))
    arm11_kernel_execute(int (*func)(void))
{
    asm volatile ("svc #0x7B \t\n"
                  "bx lr     \t\n");
}

int patch_pid() {
    // 0xFFFF9004 always points to the current KProcess
    curr_kproc = *(u32*)0xFFFF9004;
    *(u32*)(curr_kproc + KPROC_OFFSET_PID) = 0;
    return 0;
}

int unpatch_pid() {
    *(u32*)(curr_kproc + KPROC_OFFSET_PID) = self_pid;
    return 0;
}

void reinit_srv() {
    srvExit();
    srvInit();
}

void patch_srv_access() {
    svcGetProcessId(&self_pid, 0xFFFF8001);
    printf("Current process id: %lu\n", self_pid);

    printf("Patching srv access...");
    arm11_kernel_execute(patch_pid);
    reinit_srv();

    u32 new_pid;
    svcGetProcessId(&new_pid, 0xFFFF8001);
    printf("%s\n", new_pid == 0 ? "succeeded!" : "failed!");

    // Cleanup; won't take effect until srv is reinitialized
    arm11_kernel_execute(unpatch_pid);
}

int main(int argc, char** argv)
{
    gfxInitDefault();
    consoleInit(GFX_TOP, NULL);
    patch_srv_access();

    // Insert fun service stuff here

    // Main loop
    while (aptMainLoop())
    {
        hidScanInput();

        u32 kDown = hidKeysDown();
        if (kDown & KEY_START)
            break;
        gspWaitForVBlank();
    }

    gfxExit();
    return 0;
}