arch/powerpc/boot/decompress.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Wrapper around the kernel's pre-boot decompression library.
   4  *
   5  * Copyright (C) IBM Corporation 2016.
   6  */
   7
   8 #include "elf.h"
   9 #include "page.h"
  10 #include "string.h"
  11 #include "stdio.h"
  12 #include "ops.h"
  13 #include "reg.h"
  14 #include "types.h"
  15
  16 /*
  17  * The decompressor_*.c files play #ifdef games so they can be used in both
  18  * pre-boot and regular kernel code. We need these definitions to make the
  19  * includes work.
  20  */
  21
  22 #define STATIC static
  23 #define INIT
  24
  25 /*
  26  * The build process will copy the required zlib source files and headers
  27  * out of lib/ and "fix" the includes so they do not pull in other kernel
  28  * headers.
  29  */
  30
  31 #ifdef CONFIG_KERNEL_GZIP
  32 #       include "decompress_inflate.c"
  33 #endif
  34
  35 #ifdef CONFIG_KERNEL_XZ
  36 #       include "xz_config.h"
  37 #       include "../../../lib/decompress_unxz.c"
  38 #endif
  39
  40 /* globals for tracking the state of the decompression */
  41 static unsigned long decompressed_bytes;
  42 static unsigned long limit;
  43 static unsigned long skip;
  44 static char *output_buffer;
  45
  46 /*
  47  * flush() is called by __decompress() when the decompressor's scratch buffer is
  48  * full.
  49  */
  50 static long flush(void *v, unsigned long buffer_size)
  51 {
  52         unsigned long end = decompressed_bytes + buffer_size;
  53         unsigned long size = buffer_size;
  54         unsigned long offset = 0;
  55         char *in = v;
  56         char *out;
  57
  58         /*
  59          * if we hit our decompression limit, we need to fake an error to abort
  60          * the in-progress decompression.
  61          */
  62         if (decompressed_bytes >= limit)
  63                 return -1;
  64
  65         /* skip this entire block */
  66         if (end <= skip) {
  67                 decompressed_bytes += buffer_size;
  68                 return buffer_size;
  69         }
  70
  71         /* skip some data at the start, but keep the rest of the block */
  72         if (decompressed_bytes < skip && end > skip) {
  73                 offset = skip - decompressed_bytes;
  74
  75                 in += offset;
  76                 size -= offset;
  77                 decompressed_bytes += offset;
  78         }
  79
  80         out = &output_buffer[decompressed_bytes - skip];
  81         size = min(decompressed_bytes + size, limit) - decompressed_bytes;
  82
  83         memcpy(out, in, size);
  84         decompressed_bytes += size;
  85
  86         return buffer_size;
  87 }
  88
  89 static void print_err(char *s)
  90 {
  91         /* suppress the "error" when we terminate the decompressor */
  92         if (decompressed_bytes >= limit)
  93                 return;
  94
  95         printf("Decompression error: '%s'\n\r", s);
  96 }
  97
  98 /**
  99  * partial_decompress - decompresses part or all of a compressed buffer
 100  * @inbuf:       input buffer
 101  * @input_size:  length of the input buffer
 102  * @outbuf:      input buffer
 103  * @output_size: length of the input buffer
 104  * @skip         number of output bytes to ignore
 105  *
 106  * This function takes compressed data from inbuf, decompresses and write it to
 107  * outbuf. Once output_size bytes are written to the output buffer, or the
 108  * stream is exhausted the function will return the number of bytes that were
 109  * decompressed. Otherwise it will return whatever error code the decompressor
 110  * reported (NB: This is specific to each decompressor type).
 111  *
 112  * The skip functionality is mainly there so the program and discover
 113  * the size of the compressed image so that it can ask firmware (if present)
 114  * for an appropriately sized buffer.
 115  */
 116 long partial_decompress(void *inbuf, unsigned long input_size,
 117         void *outbuf, unsigned long output_size, unsigned long _skip)
 118 {
 119         int ret;
 120
 121         /*
 122          * The skipped bytes needs to be included in the size of data we want
 123          * to decompress.
 124          */
 125         output_size += _skip;
 126
 127         decompressed_bytes = 0;
 128         output_buffer = outbuf;
 129         limit = output_size;
 130         skip = _skip;
 131
 132         ret = __decompress(inbuf, input_size, NULL, flush, outbuf,
 133                 output_size, NULL, print_err);
 134
 135         /*
 136          * If decompression was aborted due to an actual error rather than
 137          * a fake error that we used to abort, then we should report it.
 138          */
 139         if (decompressed_bytes < limit)
 140                 return ret;
 141
 142         return decompressed_bytes - skip;
 143 }