misc.c

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/*
 * misc.c
 *
 * This is a collection of several routines from gzip-1.0.3
 * adapted for Linux.
 *
 * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
 * puts by Nick Holloway 1993, better puts by Martin Mares 1995
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
 */

#include "misc.h"

/* WARNING!!
 * This code is compiled with -fPIC and it is relocated dynamically
 * at run time, but no relocation processing is performed.
 * This means that it is not safe to place pointers in static structures.
 */

/*
 * Getting to provable safe in place decompression is hard.
 * Worst case behaviours need to be analyzed.
 * Background information:
 *
 * The file layout is:
 *    magic[2]
 *    method[1]
 *    flags[1]
 *    timestamp[4]
 *    extraflags[1]
 *    os[1]
 *    compressed data blocks[N]
 *    crc[4] orig_len[4]
 *
 * resulting in 18 bytes of non compressed data overhead.
 *
 * Files divided into blocks
 * 1 bit (last block flag)
 * 2 bits (block type)
 *
 * 1 block occurs every 32K -1 bytes or when there 50% compression
 * has been achieved. The smallest block type encoding is always used.
 *
 * stored:
 *    32 bits length in bytes.
 *
 * fixed:
 *    magic fixed tree.
 *    symbols.
 *
 * dynamic:
 *    dynamic tree encoding.
 *    symbols.
 *
 *
 * The buffer for decompression in place is the length of the
 * uncompressed data, plus a small amount extra to keep the algorithm safe.
 * The compressed data is placed at the end of the buffer.  The output
 * pointer is placed at the start of the buffer and the input pointer
 * is placed where the compressed data starts.  Problems will occur
 * when the output pointer overruns the input pointer.
 *
 * The output pointer can only overrun the input pointer if the input
 * pointer is moving faster than the output pointer.  A condition only
 * triggered by data whose compressed form is larger than the uncompressed
 * form.
 *
 * The worst case at the block level is a growth of the compressed data
 * of 5 bytes per 32767 bytes.
 *
 * The worst case internal to a compressed block is very hard to figure.
 * The worst case can at least be boundined by having one bit that represents
 * 32764 bytes and then all of the rest of the bytes representing the very
 * very last byte.
 *
 * All of which is enough to compute an amount of extra data that is required
 * to be safe.  To avoid problems at the block level allocating 5 extra bytes
 * per 32767 bytes of data is sufficient.  To avoind problems internal to a
 * block adding an extra 32767 bytes (the worst case uncompressed block size)
 * is sufficient, to ensure that in the worst case the decompressed data for
 * block will stop the byte before the compressed data for a block begins.
 * To avoid problems with the compressed data's meta information an extra 18
 * bytes are needed.  Leading to the formula:
 *
 * extra_bytes = (uncompressed_size >> 12) + 32768 + 18 + decompressor_size.
 *
 * Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
 * Adding 32768 instead of 32767 just makes for round numbers.
 * Adding the decompressor_size is necessary as it musht live after all
 * of the data as well.  Last I measured the decompressor is about 14K.
 * 10K of actual data and 4K of bss.
 *
 */

/*
 * gzip declarations
 */
#define STATIC      static

#undef memset
#undef memcpy
#define memzero(s, n)   memset((s), 0, (n))


static void error(char *m);

/*
 * This is set up by the setup-routine at boot-time
 */
struct boot_params *real_mode;      /* Pointer to real-mode data */

void *memset(void *s, int c, size_t n);
void *memcpy(void *dest, const void *src, size_t n);

#ifdef CONFIG_X86_64
#define memptr long
#else
#define memptr unsigned
#endif

static memptr free_mem_ptr;
static memptr free_mem_end_ptr;

static char *vidmem;
static int vidport;
static int lines, cols;

#ifdef CONFIG_KERNEL_GZIP
#include "../../../../lib/decompress_inflate.c"
#endif

#ifdef CONFIG_KERNEL_BZIP2
#include "../../../../lib/decompress_bunzip2.c"
#endif

#ifdef CONFIG_KERNEL_LZMA
#include "../../../../lib/decompress_unlzma.c"
#endif

#ifdef CONFIG_KERNEL_XZ
#include "../../../../lib/decompress_unxz.c"
#endif

#ifdef CONFIG_KERNEL_LZO
#include "../../../../lib/decompress_unlzo.c"
#endif

static void scroll(void)
{
    int i;

    memcpy(vidmem, vidmem + cols * 2, (lines - 1) * cols * 2);
    for (i = (lines - 1) * cols * 2; i < lines * cols * 2; i += 2)
        vidmem[i] = ' ';
}

#define XMTRDY          0x20

#define TXR             0       /*  Transmit register (WRITE) */
#define LSR             5       /*  Line Status               */
static void serial_putchar(int ch)
{
    unsigned timeout = 0xffff;

    while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
        cpu_relax();

    outb(ch, early_serial_base + TXR);
}

void __putstr(const char *s)
{
    int x, y, pos;
    char c;

    if (early_serial_base) {
        const char *str = s;
        while (*str) {
            if (*str == '\n')
                serial_putchar('\r');
            serial_putchar(*str++);
        }
    }

    if (real_mode->screen_info.orig_video_mode == 0 &&
        lines == 0 && cols == 0)
        return;

    x = real_mode->screen_info.orig_x;
    y = real_mode->screen_info.orig_y;

    while ((c = *s++) != '\0') {
        if (c == '\n') {
            x = 0;
            if (++y >= lines) {
                scroll();
                y--;
            }
        } else {
            vidmem[(x + cols * y) * 2] = c;
            if (++x >= cols) {
                x = 0;
                if (++y >= lines) {
                    scroll();
                    y--;
                }
            }
        }
    }

    real_mode->screen_info.orig_x = x;
    real_mode->screen_info.orig_y = y;

    pos = (x + cols * y) * 2;   /* Update cursor position */
    outb(14, vidport);
    outb(0xff & (pos >> 9), vidport+1);
    outb(15, vidport);
    outb(0xff & (pos >> 1), vidport+1);
}

void *memset(void *s, int c, size_t n)
{
    int i;
    char *ss = s;

    for (i = 0; i < n; i++)
        ss[i] = c;
    return s;
}
#ifdef CONFIG_X86_32
void *memcpy(void *dest, const void *src, size_t n)
{
    int d0, d1, d2;
    asm volatile(
        "rep ; movsl\n\t"
        "movl %4,%%ecx\n\t"
        "rep ; movsb\n\t"
        : "=&c" (d0), "=&D" (d1), "=&S" (d2)
        : "0" (n >> 2), "g" (n & 3), "1" (dest), "2" (src)
        : "memory");

    return dest;
}
#else
void *memcpy(void *dest, const void *src, size_t n)
{
    long d0, d1, d2;
    asm volatile(
        "rep ; movsq\n\t"
        "movq %4,%%rcx\n\t"
        "rep ; movsb\n\t"
        : "=&c" (d0), "=&D" (d1), "=&S" (d2)
        : "0" (n >> 3), "g" (n & 7), "1" (dest), "2" (src)
        : "memory");

    return dest;
}
#endif

static void error(char *x)
{
    error_putstr("\n\n");
    error_putstr(x);
    error_putstr("\n\n -- System halted");

    while (1)
        asm("hlt");
}

static void parse_elf(void *output)
{
#ifdef CONFIG_X86_64
    Elf64_Ehdr ehdr;
    Elf64_Phdr *phdrs, *phdr;
#else
    Elf32_Ehdr ehdr;
    Elf32_Phdr *phdrs, *phdr;
#endif
    void *dest;
    int i;

    memcpy(&ehdr, output, sizeof(ehdr));
    if (ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
       ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
       ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
       ehdr.e_ident[EI_MAG3] != ELFMAG3) {
        error("Kernel is not a valid ELF file");
        return;
    }

    debug_putstr("Parsing ELF... ");

    phdrs = malloc(sizeof(*phdrs) * ehdr.e_phnum);
    if (!phdrs)
        error("Failed to allocate space for phdrs");

    memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);

    for (i = 0; i < ehdr.e_phnum; i++) {
        phdr = &phdrs[i];

        switch (phdr->p_type) {
        case PT_LOAD:
#ifdef CONFIG_RELOCATABLE
            dest = output;
            dest += (phdr->p_paddr - LOAD_PHYSICAL_ADDR);
#else
            dest = (void *)(phdr->p_paddr);
#endif
            memcpy(dest,
                   output + phdr->p_offset,
                   phdr->p_filesz);
            break;
        default: /* Ignore other PT_* */ break;
        }
    }

    free(phdrs);
}

asmlinkage void decompress_kernel(void *rmode, memptr heap,
                  unsigned char *input_data,
                  unsigned long input_len,
                  unsigned char *output)
{
    real_mode = rmode;

    if (real_mode->screen_info.orig_video_mode == 7) {
        vidmem = (char *) 0xb0000;
        vidport = 0x3b4;
    } else {
        vidmem = (char *) 0xb8000;
        vidport = 0x3d4;
    }

    lines = real_mode->screen_info.orig_video_lines;
    cols = real_mode->screen_info.orig_video_cols;

    console_init();
    debug_putstr("early console in decompress_kernel\n");

    free_mem_ptr     = heap;    /* Heap */
    free_mem_end_ptr = heap + BOOT_HEAP_SIZE;

    if ((unsigned long)output & (MIN_KERNEL_ALIGN - 1))
        error("Destination address inappropriately aligned");
#ifdef CONFIG_X86_64
    if (heap > 0x3fffffffffffUL)
        error("Destination address too large");
#else
    if (heap > ((-__PAGE_OFFSET-(128<<20)-1) & 0x7fffffff))
        error("Destination address too large");
#endif
#ifndef CONFIG_RELOCATABLE
    if ((unsigned long)output != LOAD_PHYSICAL_ADDR)
        error("Wrong destination address");
#endif

    debug_putstr("\nDecompressing Linux... ");
    decompress(input_data, input_len, NULL, NULL, output, NULL, error);
    parse_elf(output);
    debug_putstr("done.\nBooting the kernel.\n");
    return;
}