/*
 * 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"
#include "../string.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 memcpy

/*
 * Use a normal definition of memset() from string.c. There are already
 * included header files which expect a definition of memset() and by
 * the time we define memset macro, it is too late.
 */
#undef memset
#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 */

memptr free_mem_ptr;
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

#ifdef CONFIG_KERNEL_LZ4
#include "../../../../lib/decompress_unlz4.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);
}

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

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

#if CONFIG_X86_NEED_RELOCS
static void handle_relocations(void *output, unsigned long output_len)
{
        int *reloc;
        unsigned long delta, map, ptr;
        unsigned long min_addr = (unsigned long)output;
        unsigned long max_addr = min_addr + output_len;

        /*
         * Calculate the delta between where vmlinux was linked to load
         * and where it was actually loaded.
         */
        delta = min_addr - LOAD_PHYSICAL_ADDR;
        if (!delta) {
                debug_putstr("No relocation needed... ");
                return;
        }
        debug_putstr("Performing relocations... ");

        /*
         * The kernel contains a table of relocation addresses. Those
         * addresses have the final load address of the kernel in virtual
         * memory. We are currently working in the self map. So we need to
         * create an adjustment for kernel memory addresses to the self map.
         * This will involve subtracting out the base address of the kernel.
         */
        map = delta - __START_KERNEL_map;

        /*
         * Process relocations: 32 bit relocations first then 64 bit after.
         * Three sets of binary relocations are added to the end of the kernel
         * before compression. Each relocation table entry is the kernel
         * address of the location which needs to be updated stored as a
         * 32-bit value which is sign extended to 64 bits.
         *
         * Format is:
         *
         * kernel bits...
         * 0 - zero terminator for 64 bit relocations
         * 64 bit relocation repeated
         * 0 - zero terminator for inverse 32 bit relocations
         * 32 bit inverse relocation repeated
         * 0 - zero terminator for 32 bit relocations
         * 32 bit relocation repeated
         *
         * So we work backwards from the end of the decompressed image.
         */
        for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
                int extended = *reloc;
                extended += map;

                ptr = (unsigned long)extended;
                if (ptr < min_addr || ptr > max_addr)
                        error("32-bit relocation outside of kernel!\n");

                *(uint32_t *)ptr += delta;
        }
#ifdef CONFIG_X86_64
        while (*--reloc) {
                long extended = *reloc;
                extended += map;

                ptr = (unsigned long)extended;
                if (ptr < min_addr || ptr > max_addr)
                        error("inverse 32-bit relocation outside of kernel!\n");

                *(int32_t *)ptr -= delta;
        }
        for (reloc--; *reloc; reloc--) {
                long extended = *reloc;
                extended += map;

                ptr = (unsigned long)extended;
                if (ptr < min_addr || ptr > max_addr)
                        error("64-bit relocation outside of kernel!\n");

                *(uint64_t *)ptr += delta;
        }
#endif
}
#else
static inline void handle_relocations(void *output, unsigned long output_len)
{ }
#endif

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 __visible void *decompress_kernel(void *rmode, memptr heap,
                                  unsigned char *input_data,
                                  unsigned long input_len,
                                  unsigned char *output,
                                  unsigned long output_len,
                                  unsigned long run_size)
{
        unsigned char *output_orig = output;

        real_mode = rmode;

        sanitize_boot_params(real_mode);

        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;

        /*
         * The memory hole needed for the kernel is the larger of either
         * the entire decompressed kernel plus relocation table, or the
         * entire decompressed kernel plus .bss and .brk sections.
         */
        output = choose_kernel_location(input_data, input_len, output,
                                        output_len > run_size ? output_len
                                                              : run_size);

        /* Validate memory location choices. */
        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);
        /*
         * 32-bit always performs relocations. 64-bit relocations are only
         * needed if kASLR has chosen a different load address.
         */
        if (!IS_ENABLED(CONFIG_X86_64) || output != output_orig)
                handle_relocations(output, output_len);
        debug_putstr("done.\nBooting the kernel.\n");
        return output;
}