lz4_wrapper.c

Go to the documentation of this file.

/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0-only */
 
#include <commonlib/bsd/compression.h>
#include <commonlib/bsd/helpers.h>
#include <commonlib/bsd/sysincludes.h>
#include <stdint.h>
#include <string.h>
 
/* LZ4 comes with its own supposedly portable memory access functions, but they
 * seem to be very inefficient in practice (at least on ARM64). Since coreboot
 * knows about endinaness and allows some basic assumptions (such as unaligned
 * access support), we can easily write the ones we need ourselves. */
static uint16_t LZ4_readLE16(const void *src)
{
        return le16toh(*(const uint16_t *)src);
}
static void LZ4_copy8(void *dst, const void *src)
{
/* ARM32 needs to be a special snowflake to prevent GCC from coalescing the
 * access into LDRD/STRD (which don't support unaligned accesses). */
#ifdef __arm__  /* ARMv < 6 doesn't support unaligned accesses at all. */
        #if defined(__COREBOOT_ARM_ARCH__) && __COREBOOT_ARM_ARCH__ < 6
                int i;
                for (i = 0; i < 8; i++)
                        ((uint8_t *)dst)[i] = ((uint8_t *)src)[i];
        #else
                uint32_t x0, x1;
                __asm__ ("ldr %[x0], [%[src]]"
                        : [x0]"=r"(x0)
                        : [src]"r"(src), "m"(*(const uint32_t *)src));
                __asm__ ("ldr %[x1], [%[src], #4]"
                        : [x1]"=r"(x1)
                        : [src]"r"(src), "m"(*(const uint32_t *)(src + 4)));
                __asm__ ("str %[x0], [%[dst]]"
                        : "=m"(*(uint32_t *)dst)
                        : [x0]"r"(x0), [dst]"r"(dst));
                __asm__ ("str %[x1], [%[dst], #4]"
                        : "=m"(*(uint32_t *)(dst + 4))
                        : [x1]"r"(x1), [dst]"r"(dst));
        #endif
#elif defined(__riscv)
        /* RISC-V implementations may trap on any unaligned access. */
        int i;
        for (i = 0; i < 8; i++)
                ((uint8_t *)dst)[i] = ((uint8_t *)src)[i];
#else
        *(uint64_t *)dst = *(const uint64_t *)src;
#endif
}
 
typedef  uint8_t BYTE;
typedef uint16_t U16;
typedef uint32_t U32;
typedef  int32_t S32;
typedef uint64_t U64;
 
#define FORCE_INLINE static __always_inline
#define likely(expr) __builtin_expect((expr) != 0, 1)
#define unlikely(expr) __builtin_expect((expr) != 0, 0)
 
/* Unaltered (just removed unrelated code) from github.com/Cyan4973/lz4/dev. */
#include "lz4.c.inc"    /* #include for inlining, do not link! */
 
#define LZ4F_MAGICNUMBER 0x184D2204
 
/* Bit field endianness is implementation-defined. Use masks instead.
 * https://stackoverflow.com/a/6044223 */
#define RESERVED0               0x03
#define HAS_CONTENT_CHECKSUM    0x04
#define HAS_CONTENT_SIZE        0x08
#define HAS_BLOCK_CHECKSUM      0x10
#define INDEPENDENT_BLOCKS      0x20
#define VERSION                 0xC0
#define VERSION_SHIFT           6
 
#define RESERVED1_2             0x8F
#define MAX_BLOCK_SIZE          0x70
 
struct lz4_frame_header {
        uint32_t magic;
        uint8_t flags;
        uint8_t block_descriptor;
        /* + uint64_t content_size iff has_content_size is set */
        /* + uint8_t header_checksum */
} __packed;
 
#define BH_SIZE                 0x7FFFFFFF
#define NOT_COMPRESSED          0x80000000
 
struct lz4_block_header {
        uint32_t raw;
        /* + size bytes of data */
        /* + uint32_t block_checksum iff has_block_checksum is set */
} __packed;
 
size_t ulz4fn(const void *src, size_t srcn, void *dst, size_t dstn)
{
        const void *in = src;
        void *out = dst;
        size_t out_size = 0;
        int has_block_checksum;
 
        { /* With in-place decompression the header may become invalid later. */
                const struct lz4_frame_header *h = in;
 
                if (srcn < sizeof(*h) + sizeof(uint64_t) + sizeof(uint8_t))
                        return 0;       /* input overrun */
 
                /* We assume there's always only a single, standard frame. */
                if (le32toh(h->magic) != LZ4F_MAGICNUMBER
                    || (h->flags & VERSION) != (1 << VERSION_SHIFT))
                        return 0;       /* unknown format */
                if ((h->flags & RESERVED0) || (h->block_descriptor & RESERVED1_2))
                        return 0;       /* reserved must be zero */
                if (!(h->flags & INDEPENDENT_BLOCKS))
                        return 0;       /* we don't support block dependency */
                has_block_checksum = h->flags & HAS_BLOCK_CHECKSUM;
 
                in += sizeof(*h);
                if (h->flags & HAS_CONTENT_SIZE)
                        in += sizeof(uint64_t);
                in += sizeof(uint8_t);
        }
 
        while (1) {
                if ((size_t)(in - src) + sizeof(struct lz4_block_header) > srcn)
                        break;          /* input overrun */
 
                struct lz4_block_header b = {
                        .raw = le32toh(*(const uint32_t *)in)
                };
                in += sizeof(struct lz4_block_header);
 
                if ((size_t)(in - src) + (b.raw & BH_SIZE) > srcn)
                        break;                  /* input overrun */
 
                if (!(b.raw & BH_SIZE)) {
                        out_size = out - dst;
                        break;                  /* decompression successful */
                }
 
                if (b.raw & NOT_COMPRESSED) {
                        size_t size = MIN((uintptr_t)(b.raw & BH_SIZE), (uintptr_t)dst
                                + dstn - (uintptr_t)out);
                        memcpy(out, in, size);
                        if (size < (b.raw & BH_SIZE))
                                break;          /* output overrun */
                        out += size;
                } else {
                        /* constant folding essential, do not touch params! */
                        int ret = LZ4_decompress_generic(in, out, (b.raw & BH_SIZE),
                                        dst + dstn - out, endOnInputSize,
                                        full, 0, noDict, out, NULL, 0);
                        if (ret < 0)
                                break;          /* decompression error */
                        out += ret;
                }
 
                in += (b.raw & BH_SIZE);
                if (has_block_checksum)
                        in += sizeof(uint32_t);
        }
 
        return out_size;
}
 
size_t ulz4f(const void *src, void *dst)
{
        /* LZ4 uses signed size parameters, so can't just use ((u32)-1) here. */
        return ulz4fn(src, 1*GiB, dst, 1*GiB);
}