stage0 compiler doesn't work on x86_64 debian wheezy

[brson]

It hangs before the Rust main function when building core.

[shizmob]

Runtime log (RUST_LOG=::rt):

rust: new dom 0x1fbfbb0
rust: created task thread: 0x1fbfba0, id: 0, live_threads: 1
rust: Disallowing osmain scheduler to exit
rust: new dom 0x1fc1150
rust: created task thread: 0x1fc1140, id: 0, live_threads: 1
rust: Creating task main, on thread 0.
rust: Registering task
rust: New non-weak tasks 1
rust: new task 0x1fc25b0
rust: sizeof(task) = 736 (0x2e0)
rust: creating new stack for task 1fc25b0
rust: calculating new stack size for 0x1fc25b0
rust: min: 768 current: 0 requested: 768
rust: next stack size: 768
rust: new stk 0x1fc28f0
rust: stk end 0x1fc3420
rust: created task: 0x1fc25b0, spawner: (none), name: main
rust: startup: 8 args in 0x1fc3460
rust: startup: arg[0] = 'x86_64-unknown-linux-gnu/stage0/bin/rustc'
rust: startup: arg[1] = '--cfg'
rust: startup: arg[2] = 'stage0'
rust: startup: arg[3] = '-O'
rust: startup: arg[4] = '--target=x86_64-unknown-linux-gnu'
rust: startup: arg[5] = '-o'
rust: startup: arg[6] = 'x86_64-unknown-linux-gnu/stage0/lib/rustc/x86_64-unknown-linux-gnu/lib/libcore.so'
rust: startup: arg[7] = '/root/rust/rust/src/libcore/core.rc'
rust: starting task from fn 0x4110a0 with env 0x0 and arg 0x1fc3460
rust: task main 0x1fc1150 state change 'newborn' -> 'running' while in 'newborn'
rust: pumping scheduler
rust: scheduler 0 resuming ...
rust: worker 0, number_of_live_tasks = 0
rust: all tasks are blocked, scheduler id 0 yielding ...
rust: blocking scheduler

It seems to be some kind of deadlock as the only thread is hanging in pthread_wait.

[shizmob]

The machine is also running on a GRSecurity-patched kernel, although I don't get any grsec kernel logs during the compilation progress it might be an obscure intervention.

[brson]

Oh, that's interesting. We have another report that rustc doesn't work with PAX kernels.

[brson]

I guess GRSecurity and PAX are the same thing? #1708

[shizmob]

PaX is generally a part of GRSecurity, yes.
Marking the rustc binary with MPROTECT disabled (paxctl -cm /path/to/rustc) causes the compiler to work fine. :)

I'd recommend detecting if paxctl is installed and if GRSecurity is activated (you could try probing if /proc/sys/kernel/grsecurity exists) and then mark appropriately? You do need root privileges to use paxctl.

[graydon]

We should fix this in general. I'll try to remember to put a grsec kernel into the buildbot cluster for part of the breadth testing. It's common enough and we really ought to be able to live with it.

[graydon]

Fixed.