alistair23-linux/arch/um/kernel/um_arch.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <linux/delay.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/utsname.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/kmsg_dump.h>

#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <as-layout.h>
#include <arch.h>
#include <init.h>
#include <kern.h>
#include <kern_util.h>
#include <mem_user.h>
#include <os.h>

#define DEFAULT_COMMAND_LINE "root=98:0"

/* Changed in add_arg and setup_arch, which run before SMP is started */
static char __initdata command_line[COMMAND_LINE_SIZE] = { 0 };

static void __init add_arg(char *arg)
{
	if (strlen(command_line) + strlen(arg) + 1 > COMMAND_LINE_SIZE) {
		os_warn("add_arg: Too many command line arguments!\n");
		exit(1);
	}
	if (strlen(command_line) > 0)
		strcat(command_line, " ");
	strcat(command_line, arg);
}

/*
 * These fields are initialized at boot time and not changed.
 * XXX This structure is used only in the non-SMP case.  Maybe this
 * should be moved to smp.c.
 */
struct cpuinfo_um boot_cpu_data = {
	.loops_per_jiffy	= 0,
	.ipi_pipe		= { -1, -1 }
};

union thread_union cpu0_irqstack
	__attribute__((__section__(".data..init_irqstack"))) =
		{ .thread_info = INIT_THREAD_INFO(init_task) };

/* Changed in setup_arch, which is called in early boot */
static char host_info[(__NEW_UTS_LEN + 1) * 5];

static int show_cpuinfo(struct seq_file *m, void *v)
{
	int index = 0;

	seq_printf(m, "processor\t: %d\n", index);
	seq_printf(m, "vendor_id\t: User Mode Linux\n");
	seq_printf(m, "model name\t: UML\n");
	seq_printf(m, "mode\t\t: skas\n");
	seq_printf(m, "host\t\t: %s\n", host_info);
	seq_printf(m, "bogomips\t: %lu.%02lu\n\n",
		   loops_per_jiffy/(500000/HZ),
		   (loops_per_jiffy/(5000/HZ)) % 100);

	return 0;
}

static void *c_start(struct seq_file *m, loff_t *pos)
{
	return *pos < NR_CPUS ? cpu_data + *pos : NULL;
}

static void *c_next(struct seq_file *m, void *v, loff_t *pos)
{
	++*pos;
	return c_start(m, pos);
}

static void c_stop(struct seq_file *m, void *v)
{
}

const struct seq_operations cpuinfo_op = {
	.start	= c_start,
	.next	= c_next,
	.stop	= c_stop,
	.show	= show_cpuinfo,
};

/* Set in linux_main */
unsigned long uml_physmem;
EXPORT_SYMBOL(uml_physmem);

unsigned long uml_reserved; /* Also modified in mem_init */
unsigned long start_vm;
unsigned long end_vm;

/* Set in uml_ncpus_setup */
int ncpus = 1;

/* Set in early boot */
static int have_root __initdata = 0;

/* Set in uml_mem_setup and modified in linux_main */
long long physmem_size = 32 * 1024 * 1024;
EXPORT_SYMBOL(physmem_size);

static const char *usage_string =
"User Mode Linux v%s\n"
"	available at http://user-mode-linux.sourceforge.net/\n\n";

static int __init uml_version_setup(char *line, int *add)
{
	/* Explicitly use printf() to show version in stdout */
	printf("%s\n", init_utsname()->release);
	exit(0);

	return 0;
}

__uml_setup("--version", uml_version_setup,
"--version\n"
"    Prints the version number of the kernel.\n\n"
);

static int __init uml_root_setup(char *line, int *add)
{
	have_root = 1;
	return 0;
}

__uml_setup("root=", uml_root_setup,
"root=<file containing the root fs>\n"
"    This is actually used by the generic kernel in exactly the same\n"
"    way as in any other kernel. If you configure a number of block\n"
"    devices and want to boot off something other than ubd0, you \n"
"    would use something like:\n"
"        root=/dev/ubd5\n\n"
);

static int __init no_skas_debug_setup(char *line, int *add)
{
	os_warn("'debug' is not necessary to gdb UML in skas mode - run\n");
	os_warn("'gdb linux'\n");

	return 0;
}

__uml_setup("debug", no_skas_debug_setup,
"debug\n"
"    this flag is not needed to run gdb on UML in skas mode\n\n"
);

static int __init Usage(char *line, int *add)
{
	const char **p;

	printf(usage_string, init_utsname()->release);
	p = &__uml_help_start;
	/* Explicitly use printf() to show help in stdout */
	while (p < &__uml_help_end) {
		printf("%s", *p);
		p++;
	}
	exit(0);
	return 0;
}

__uml_setup("--help", Usage,
"--help\n"
"    Prints this message.\n\n"
);

static void __init uml_checksetup(char *line, int *add)
{
	struct uml_param *p;

	p = &__uml_setup_start;
	while (p < &__uml_setup_end) {
		size_t n;

		n = strlen(p->str);
		if (!strncmp(line, p->str, n) && p->setup_func(line + n, add))
			return;
		p++;
	}
}

static void __init uml_postsetup(void)
{
	initcall_t *p;

	p = &__uml_postsetup_start;
	while (p < &__uml_postsetup_end) {
		(*p)();
		p++;
	}
	return;
}

static int panic_exit(struct notifier_block *self, unsigned long unused1,
		      void *unused2)
{
	kmsg_dump(KMSG_DUMP_PANIC);
	bust_spinlocks(1);
	bust_spinlocks(0);
	uml_exitcode = 1;
	os_dump_core();
	return 0;
}

static struct notifier_block panic_exit_notifier = {
	.notifier_call 		= panic_exit,
	.next 			= NULL,
	.priority 		= 0
};

void uml_finishsetup(void)
{
	atomic_notifier_chain_register(&panic_notifier_list,
				       &panic_exit_notifier);

	uml_postsetup();

	new_thread_handler();
}

/* Set during early boot */
unsigned long task_size;
EXPORT_SYMBOL(task_size);

unsigned long host_task_size;

unsigned long brk_start;
unsigned long end_iomem;
EXPORT_SYMBOL(end_iomem);

#define MIN_VMALLOC (32 * 1024 * 1024)

int __init linux_main(int argc, char **argv)
{
	unsigned long avail, diff;
	unsigned long virtmem_size, max_physmem;
	unsigned long stack;
	unsigned int i;
	int add;

	for (i = 1; i < argc; i++) {
		if ((i == 1) && (argv[i][0] == ' '))
			continue;
		add = 1;
		uml_checksetup(argv[i], &add);
		if (add)
			add_arg(argv[i]);
	}
	if (have_root == 0)
		add_arg(DEFAULT_COMMAND_LINE);

	host_task_size = os_get_top_address();
	/*
	 * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
	 * out
	 */
	task_size = host_task_size & PGDIR_MASK;

	/* OS sanity checks that need to happen before the kernel runs */
	os_early_checks();

	brk_start = (unsigned long) sbrk(0);

	/*
	 * Increase physical memory size for exec-shield users
	 * so they actually get what they asked for. This should
	 * add zero for non-exec shield users
	 */

	diff = UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
	if (diff > 1024 * 1024) {
		os_info("Adding %ld bytes to physical memory to account for "
			"exec-shield gap\n", diff);
		physmem_size += UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
	}

	uml_physmem = (unsigned long) __binary_start & PAGE_MASK;

	/* Reserve up to 4M after the current brk */
	uml_reserved = ROUND_4M(brk_start) + (1 << 22);

	setup_machinename(init_utsname()->machine);

	highmem = 0;
	iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK;
	max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC;

	/*
	 * Zones have to begin on a 1 << MAX_ORDER page boundary,
	 * so this makes sure that's true for highmem
	 */
	max_physmem &= ~((1 << (PAGE_SHIFT + MAX_ORDER)) - 1);
	if (physmem_size + iomem_size > max_physmem) {
		highmem = physmem_size + iomem_size - max_physmem;
		physmem_size -= highmem;
	}

	high_physmem = uml_physmem + physmem_size;
	end_iomem = high_physmem + iomem_size;
	high_memory = (void *) end_iomem;

	start_vm = VMALLOC_START;

	virtmem_size = physmem_size;
	stack = (unsigned long) argv;
	stack &= ~(1024 * 1024 - 1);
	avail = stack - start_vm;
	if (physmem_size > avail)
		virtmem_size = avail;
	end_vm = start_vm + virtmem_size;

	if (virtmem_size < physmem_size)
		os_info("Kernel virtual memory size shrunk to %lu bytes\n",
			virtmem_size);

	os_flush_stdout();

	return start_uml();
}

int __init __weak read_initrd(void)
{
	return 0;
}

void __init setup_arch(char **cmdline_p)
{
	stack_protections((unsigned long) &init_thread_info);
	setup_physmem(uml_physmem, uml_reserved, physmem_size, highmem);
	mem_total_pages(physmem_size, iomem_size, highmem);
	read_initrd();

	paging_init();
	strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
	*cmdline_p = command_line;
	setup_hostinfo(host_info, sizeof host_info);
}

void __init check_bugs(void)
{
	arch_check_bugs();
	os_check_bugs();
}

void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
}