54 lines
1.6 KiB
C
54 lines
1.6 KiB
C
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/* Verifies that mmap'd regions are only written back on munmap
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if the data was actually modified in memory. */
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#include <string.h>
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#include <syscall.h>
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#include "tests/vm/sample.inc"
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#include "tests/lib.h"
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#include "tests/main.h"
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void
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test_main (void)
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{
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static const char overwrite[] = "Now is the time for all good...";
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static char buffer[sizeof sample - 1];
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char *actual = (char *) 0x54321000;
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int handle;
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mapid_t map;
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/* Open file, map, verify data. */
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CHECK ((handle = open ("sample.txt")) > 1, "open \"sample.txt\"");
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CHECK ((map = mmap (handle, actual)) != MAP_FAILED, "mmap \"sample.txt\"");
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if (memcmp (actual, sample, strlen (sample)))
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fail ("read of mmap'd file reported bad data");
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/* Modify file. */
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CHECK (write (handle, overwrite, strlen (overwrite))
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== (int) strlen (overwrite),
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"write \"sample.txt\"");
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/* Close mapping. Data should not be written back, because we
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didn't modify it via the mapping. */
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msg ("munmap \"sample.txt\"");
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munmap (map);
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/* Read file back. */
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msg ("seek \"sample.txt\"");
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seek (handle, 0);
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CHECK (read (handle, buffer, sizeof buffer) == sizeof buffer,
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"read \"sample.txt\"");
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/* Verify that file overwrite worked. */
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if (memcmp (buffer, overwrite, strlen (overwrite))
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|| memcmp (buffer + strlen (overwrite), sample + strlen (overwrite),
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strlen (sample) - strlen (overwrite)))
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{
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if (!memcmp (buffer, sample, strlen (sample)))
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fail ("munmap wrote back clean page");
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else
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fail ("read surprising data from file");
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}
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else
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msg ("file change was retained after munmap");
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}
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