qemu-user-i386: unable to reserve virtual address space

[easyaspi314]

Problem description

Trying to run any binary in qemu-user-i386 results in this error:

qemu-i386: Unable to reserve 0xfffff000 bytes of virtual address space at 0x1000 (Success) for use as guest address space (check yourvirtual memory ulimit setting, min_mmap_addr or reserve less using -R option)

Note that the -R option does not fix the problem. It is either too small or it throws the same error.

It seems that the "Success" part is the result of strerror(errno), but errno == 0

Steps to reproduce

1. Install qemu-user-i386
2. Compile and try to run any random i386 binary. For example, the bare minimum which just syscalls exit(0):

    .globl _start
_start:
    movl $1, %eax # SYS_exit
    xorl %ebx, %ebx
    int $0x80

$ clang --target=i386-linux-gnu -nostdlib -static -fuse-ld=$(which ld.lld) no-op.s -o no-op
$ qemu-i386 -cpu max ./no-op

Expected behavior

It runs as expected.

Additional information

Note that it is impossible to read the vm.mmap_min_addr sysctl without root on my device.

Packages CPU architecture:
aarch64
Subscribed repositories:
# sources.list
deb https://grimler.se/termux-packages-24/ stable main
# science-repo (sources.list.d/science.list)
deb https://dl.bintray.com/grimler/science-packages-24 science stable
# game-repo (sources.list.d/game.list)
deb https://dl.bintray.com/grimler/game-packages-24 games stable
# x11-repo (sources.list.d/x11.list)
deb https://dl.bintray.com/xeffyr/x11-packages x11 main
# unstable-repo (sources.list.d/unstable.list)
deb https://dl.bintray.com/xeffyr/unstable-packages unstable main
# sources.list.d/pointless.list
deb https://its-pointless.github.io/files/24 termux extras
Updatable packages:
libcairo/stable 1.16.0-7 aarch64 [upgradable from: 1.16.0-2]
pulseaudio/stable 14.0 aarch64 [upgradable from: 12.2-21]
Android version:
11
Kernel build information:
Linux localhost 4.4.223-g52750b8f2138-ab6846512 #1 SMP PREEMPT Fri Sep 18 09:49:34 UTC 2020 aarch64 Android
Device manufacturer:
Google
Device model:
Pixel 2 XL

[ghost]

That's a quite strange error. I didn't observed it on my device and x86 binaries are executed fine both on AArch64 and ARM devices.

[ghost]

Problem is that it tries to read vm.mmap_min_addr which is not accessible on devices where SELinux is strict regarding sysctl.

I have added a patch which changes a fallback value from 4096 (1 page) to 32768 (8 pages) as in sysctl vm.mmap_min_addr on my device.

[easyaspi314]

That seems to work, thanks.