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99 lines
2.3 KiB
99 lines
2.3 KiB
3 months ago
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/*
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* LiZaRd -- Fast compression method based on Lempel-Ziv 77
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*
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* (c) 2004, Robert Spalek <robert@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#include <ucw/lib.h>
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#include <ucw/threads.h>
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#include <ucw/sighandler.h>
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#include <ucw/lizard.h>
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#include <sys/mman.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <setjmp.h>
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#include <errno.h>
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struct lizard_buffer {
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uint len;
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void *ptr;
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};
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struct lizard_buffer *
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lizard_alloc(void)
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{
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struct lizard_buffer *buf = xmalloc(sizeof(struct lizard_buffer));
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buf->len = 0;
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buf->ptr = NULL;
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handle_signal(SIGSEGV);
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return buf;
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}
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void
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lizard_free(struct lizard_buffer *buf)
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{
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unhandle_signal(SIGSEGV);
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if (buf->ptr)
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munmap(buf->ptr, buf->len + CPU_PAGE_SIZE);
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xfree(buf);
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}
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static void
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lizard_realloc(struct lizard_buffer *buf, uint max_len)
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/* max_len needs to be aligned to CPU_PAGE_SIZE */
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{
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if (max_len <= buf->len)
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return;
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if (max_len < 2*buf->len) // to ensure logarithmic cost
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max_len = 2*buf->len;
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if (buf->ptr)
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munmap(buf->ptr, buf->len + CPU_PAGE_SIZE);
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buf->len = max_len;
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buf->ptr = mmap(NULL, buf->len + CPU_PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
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if (buf->ptr == MAP_FAILED)
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die("mmap(anonymous, %d bytes): %m", (uint)(buf->len + CPU_PAGE_SIZE));
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if (mprotect(buf->ptr + buf->len, CPU_PAGE_SIZE, PROT_NONE) < 0)
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die("mprotect: %m");
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}
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static jmp_buf safe_decompress_jump;
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static int
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sigsegv_handler(int signal UNUSED)
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{
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longjmp(safe_decompress_jump, 1);
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return 1;
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}
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byte *
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lizard_decompress_safe(const byte *in, struct lizard_buffer *buf, uint expected_length)
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{
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uint lock_offset = ALIGN_TO(expected_length + 3, CPU_PAGE_SIZE); // +3 due to the unaligned access
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if (lock_offset > buf->len)
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lizard_realloc(buf, lock_offset);
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volatile ucw_sighandler_t old_handler = set_signal_handler(SIGSEGV, sigsegv_handler);
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byte *ptr;
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if (!setjmp(safe_decompress_jump))
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{
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ptr = buf->ptr + buf->len - lock_offset;
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int len = lizard_decompress(in, ptr);
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if (len != (int) expected_length)
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{
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ptr = NULL;
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errno = EINVAL;
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}
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}
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else
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{
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msg(L_ERROR, "SIGSEGV caught in lizard_decompress()");
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ptr = NULL;
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errno = EFAULT;
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}
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set_signal_handler(SIGSEGV, old_handler);
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return ptr;
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}
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