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qemu-user: mmap should return failure (MAP_FAILED, -1) instead of success (NULL, 0) when len==0
As shown in https://github.com/beehive-lab/mambo/issues/19#issuecomment-407420602, with len==0 mmap returns success (NULL, 0) instead of failure (MAP_FAILED, -1) in a x86_64 host executing a ELF 64-bit LSB executable, ARM aarch64 binary.
Steps to reproduce the bug:
- (cross-)compile the attached source file:
$ aarch64-linux-gnu-gcc -static -std=gnu99 -lpthread test/mmap_qemu.c -o mmap_qemu
- Execute in a x86_64 host with qemu-user and qemu-user-binfmt:
$ ./mmap_qemu
alloc: 0
MAP_FAILED: -1
errno: 0
mmap_qemu: test/mmap_qemu.c:15: main: Assertion `alloc == MAP_FAILED' failed.
qemu: uncaught target signal 6 (Aborted) - core dumped
Aborted (core dumped)
- Execute in a ARM host without any additional dependecy:
$ ./mmap_qemu
alloc: -1
MAP_FAILED: -1
errno: 22
The bug is present in Fedora:
$ qemu-aarch64 --version
qemu-aarch64 version 2.11.2(qemu-2.11.2-1.fc28)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
$ uname -r
4.17.7-200.fc28.x86_64
And also in Ubuntu:
$ qemu-aarch64 --version
qemu-aarch64 version 2.12.0 (Debian 1:2.12+dfsg-3ubuntu3)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
$ uname -r
4.15.0-23-generic
Possibly related to:
- https://lists.freebsd.org/pipermail/freebsd-hackers/2009-July/029109.html
- https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=203852
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