[Libguestfs] [PATCH nbdkit] pattern: Accurately update b & offset in loop

It's better to update the 'b' pointer and the 'offset' using the calculated increment 'n', rather than using '8-o' which might be larger than the remainder of the buffer. Previously we could create a dangling pointer beyond the end of the output buffer, and this should not matter, but it's best not to do this if we can easily avoid it. Also improve the test by replacing qemu-io with nbdsh. It is able to make non-aligned requests so we can now test those. --- plugins/pattern/pattern.c | 4 +- tests/test-pattern.sh | 98 ++++++++++++++++++--------------------- 2 files changed, 46 insertions(+), 56 deletions(-) diff --git a/plugins/pattern/pattern.c b/plugins/pattern/pattern.c index 3d2bb6040..3db1a21eb 100644 --- a/plugins/pattern/pattern.c +++ b/plugins/pattern/pattern.c @@ -119,8 +119,8 @@ pattern_pread (void *handle, void *buf, uint32_t count, uint64_t offset, o = offset & 7; n = MIN (count, 8-o); memcpy (b, (char *)&d + o, n); - b += 8-o; - offset += 8-o; + b += n; + offset += n; count -= n; } diff --git a/tests/test-pattern.sh b/tests/test-pattern.sh index 1b1bd56fb..6025aea78 100755 --- a/tests/test-pattern.sh +++ b/tests/test-pattern.sh @@ -31,61 +31,51 @@ # SUCH DAMAGE. # Test the pattern plugin. -# -# Note we don't have any client which can issue misaligned NBD -# requests. qemu-io will issue 512-byte aligned requests no matter -# what read parameters we give it. Hence these tests are rather -# limited. (XXX) source ./functions.sh set -e -requires qemu-io --version - -sock=$(mktemp -u /tmp/nbdkit-test-sock.XXXXXX) -files="pattern.out pattern.pid $sock" -rm -f $files -cleanup_fn rm -f $files - -# Run nbdkit with pattern plugin. -start_nbdkit -P pattern.pid -U $sock pattern 1G - -qemu-io -r -f raw "nbd+unix://?socket=$sock" \ - -c 'r -v 0 512' | grep -E '^[[:xdigit:]]+:' > pattern.out -if [ "$(cat pattern.out)" != "00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 ................ -00000010: 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00 18 ................ -00000020: 00 00 00 00 00 00 00 20 00 00 00 00 00 00 00 28 ................ -00000030: 00 00 00 00 00 00 00 30 00 00 00 00 00 00 00 38 .......0.......8 -00000040: 00 00 00 00 00 00 00 40 00 00 00 00 00 00 00 48 ...............H -00000050: 00 00 00 00 00 00 00 50 00 00 00 00 00 00 00 58 .......P.......X -00000060: 00 00 00 00 00 00 00 60 00 00 00 00 00 00 00 68 ...............h -00000070: 00 00 00 00 00 00 00 70 00 00 00 00 00 00 00 78 .......p.......x -00000080: 00 00 00 00 00 00 00 80 00 00 00 00 00 00 00 88 ................ -00000090: 00 00 00 00 00 00 00 90 00 00 00 00 00 00 00 98 ................ -000000a0: 00 00 00 00 00 00 00 a0 00 00 00 00 00 00 00 a8 ................ -000000b0: 00 00 00 00 00 00 00 b0 00 00 00 00 00 00 00 b8 ................ -000000c0: 00 00 00 00 00 00 00 c0 00 00 00 00 00 00 00 c8 ................ -000000d0: 00 00 00 00 00 00 00 d0 00 00 00 00 00 00 00 d8 ................ -000000e0: 00 00 00 00 00 00 00 e0 00 00 00 00 00 00 00 e8 ................ -000000f0: 00 00 00 00 00 00 00 f0 00 00 00 00 00 00 00 f8 ................ -00000100: 00 00 00 00 00 00 01 00 00 00 00 00 00 00 01 08 ................ -00000110: 00 00 00 00 00 00 01 10 00 00 00 00 00 00 01 18 ................ -00000120: 00 00 00 00 00 00 01 20 00 00 00 00 00 00 01 28 ................ -00000130: 00 00 00 00 00 00 01 30 00 00 00 00 00 00 01 38 .......0.......8 -00000140: 00 00 00 00 00 00 01 40 00 00 00 00 00 00 01 48 ...............H -00000150: 00 00 00 00 00 00 01 50 00 00 00 00 00 00 01 58 .......P.......X -00000160: 00 00 00 00 00 00 01 60 00 00 00 00 00 00 01 68 ...............h -00000170: 00 00 00 00 00 00 01 70 00 00 00 00 00 00 01 78 .......p.......x -00000180: 00 00 00 00 00 00 01 80 00 00 00 00 00 00 01 88 ................ -00000190: 00 00 00 00 00 00 01 90 00 00 00 00 00 00 01 98 ................ -000001a0: 00 00 00 00 00 00 01 a0 00 00 00 00 00 00 01 a8 ................ -000001b0: 00 00 00 00 00 00 01 b0 00 00 00 00 00 00 01 b8 ................ -000001c0: 00 00 00 00 00 00 01 c0 00 00 00 00 00 00 01 c8 ................ -000001d0: 00 00 00 00 00 00 01 d0 00 00 00 00 00 00 01 d8 ................ -000001e0: 00 00 00 00 00 00 01 e0 00 00 00 00 00 00 01 e8 ................ -000001f0: 00 00 00 00 00 00 01 f0 00 00 00 00 00 00 01 f8 ................" ] -then - echo "$0: unexpected pattern:" - cat pattern.out - exit 1 -fi +requires_run +requires_nbdsh_uri + +nbdkit pattern 2M --run 'nbdsh -u "$uri" -c -' <<EOF + +# Read from an aligned offset at the beginning of the disk. +expected = bytearray() +for i in range(0,64,8): + expected = expected + i.to_bytes(8, "big") +print("expected = %r" % expected) +actual = h.pread(64, 0) +print("actual = %r" % actual) +assert actual == expected + +# Read from an unaligned offset. +actual = bytearray(4) + h.pread(60, 4) +print("actual = %r" % actual) +assert actual == expected + +# Read to an unaligned offset. +actual = h.pread(60, 0) +print("actual = %r" % actual) +assert actual == expected[:60] + +# Read from an aligned offset further in the disk. +expected = bytearray() +for i in range(1000000,1000064,8): + expected = expected + i.to_bytes(8, "big") +print("expected = %r" % expected) +actual = h.pread(64, 1000000) +print("actual = %r" % actual) +assert actual == expected + +# Read from an unaligned offset. +actual = bytearray(3) + h.pread(61, 1000003) +print("actual = %r" % actual) +assert actual == expected + +# Read to an unaligned offset. +actual = h.pread(60, 1000000) +print("actual = %r" % actual) +assert actual == expected[:60] + +'EOF' -- 2.42.0