0256a6ac4b
The dcache (code/stack cache) is supposed to be transparent, but it's actually not in one case. dcache tries to read chunks (cache lines) at a time off of the target. This may end up trying to read unaccessible or unavailable memory. Currently the caller gets an xfer error in this case. But if the specific bits of memory the caller actually wanted are available and accessible, then the caller should get the memory it wanted, not an error. gdb/ 2014-05-21 Pedro Alves <palves@redhat.com> * dcache.c (dcache_read_memory_partial): If reading the cache line fails, fallback to reading just the memory the caller wanted. gdb/testsuite/ 2014-05-21 Pedro Alves <palves@redhat.com> * gdb.base/dcache-line-read-error.c: New. * gdb.base/dcache-line-read-error.exp: New.
107 lines
2.7 KiB
C
107 lines
2.7 KiB
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 2012-2014 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <stdlib.h>
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#include <stdio.h>
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#include <sys/mman.h>
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#include <unistd.h>
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#include <string.h>
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size_t pg_size;
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void *first_mapped_page;
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void *last_mapped_page;
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void
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breakpt (void)
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{
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/* Nothing. */
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}
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int
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main (void)
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{
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void *p;
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int pg_count;
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size_t i;
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/* Map 6 contiguous pages, and then unmap all second first, and
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second last.
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From GDB we will disassemble each of the _mapped_ pages, with a
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code-cache (dcache) line size bigger than the page size (twice
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bigger). This makes GDB try to read one page before the mapped
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page once, and the page after another time. GDB should give no
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error in either case.
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That is, depending on where the kernel aligns the pages, we get
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either:
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.---.---.---.---.---.---.
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| U | M | U | U | M | U |
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'---'---'---'---'---'---.
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| | | | <- line alignment
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^^^^^^^ ^^^^^^^
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| |
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+ line1 + line2
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Or:
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.---.---.---.---.---.---.
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| U | M | U | U | M | U |
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'---'---'---'---'---'---.
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| | | <- line alignment
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^^^^^^^ ^^^^^^^
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line1 + + line2
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Note we really want to test that dcache behaves correctly when
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reading a cache line fails. We're just using unmapped memory as
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proxy for any kind of error. */
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pg_size = getpagesize ();
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pg_count = 6;
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p = mmap (0, pg_count * pg_size, PROT_READ|PROT_WRITE,
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MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
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if (p == MAP_FAILED)
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{
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perror ("mmap");
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return EXIT_FAILURE;
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}
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/* Leave memory zero-initialized. Disassembling 0s should behave on
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all targets. */
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for (i = 0; i < pg_count; i++)
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{
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if (i == 1 || i == 4)
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continue;
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if (munmap (p + (i * pg_size), pg_size) == -1)
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{
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perror ("munmap");
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return EXIT_FAILURE;
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}
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}
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first_mapped_page = p + 1 * pg_size;;
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last_mapped_page = p + 4 * pg_size;
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breakpt ();
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return EXIT_SUCCESS;
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}
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