We know that all lines from /proc/<PID>/maps end in a newline, so we
trim exactly that one byte, then we put it all back together with
.join('\n') to check if we've read the entire file.
Linux virtual files are usually served in 4 kB increments; tst_qfile's
maps file is about 16000 bytes for me, just short of the QIODevice buffer:
[pid 414315] read(5, "55c6afe04000-55c6afe11000 r--p 0"..., 16384) = 4049
[pid 414315] read(5, "7f215fd25000-7f215fd26000 r--p 0"..., 12335) = 4038
[pid 414315] read(5, "7f2160800000-7f21608c7000 r--p 0"..., 8297) = 4072
[pid 414315] read(5, "7f216119f000-7f21611a0000 rw-p 0"..., 4225) = 3994
It is not a coincidence that the reads are at line boundaries, though
it's not a guarantee from the kernel.
We appear to have accidentally fixed the QEMU emulation bug by reading
another process' /proc/<PID>/maps (hypothesis: QMU emulates the target
system in /proc/self, hiding itself in maps, but makes no translation
for other process map files.
Change-Id: Ifbf974a4d10745b099b1fffd1777ac919b12dc90
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
7ca82250e0