Re: [LTP] [EXT] Re: [PATCH v9 00/24] ILP32 for ARM64

[Yury Norov]

On Tue, May 14, 2019 at 12:43:11PM +0200, Cyril Hrubis wrote:
> Hi!
> > > There is a problem with the stack size accounting during execve when
> > > there is no stack limit:
> > >
> > > $ ulimit -s
> > > 8192
> > > $ ./hello.ilp32 
> > > Hello World!
> > > $ ulimit -s unlimited
> > > $ ./hello.ilp32 
> > > Segmentation fault
> > > $ strace ./hello.ilp32 
> > > execve("./hello.ilp32", ["./hello.ilp32"], 0xfffff10548f0 /* 77 vars */) = -1 ENOMEM (Cannot allocate memory)
> > > +++ killed by SIGSEGV +++
> > > Segmentation fault (core dumped)
> > >
> > > Andreas.
> > 
> > Thanks Andreas, I will take a look. Do we have such test in LTP?

So the problem was in not converting new compat-sensitive code:

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 5bdf357169d8..c509f83fa506 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -63,7 +63,7 @@
 				TASK_SIZE_32 : TASK_SIZE_64)
 #define TASK_SIZE_OF(tsk)	(is_compat_thread(tsk) ? \
 				TASK_SIZE_32 : TASK_SIZE_64)
-#define DEFAULT_MAP_WINDOW	(test_thread_flag(TIF_32BIT) ? \
+#define DEFAULT_MAP_WINDOW	(is_compat_task() ? \
 				TASK_SIZE_32 : DEFAULT_MAP_WINDOW_64)
 #else
 #define TASK_SIZE		TASK_SIZE_64

The fix is incorporated in ilp32-5.1.1:
https://github.com/norov/linux/tree/ilp32-5.1.1

> We do have a test that we can run a binary with very small stack size
> i.e. 512kB but there does not seem to be anything that would catch this
> specific problem.
> 
> Can you please open an issue and describe how to reproduce the problem
> at our github tracker:
> 
> https://github.com/linux-test-project/ltp/issues
> 
> Then we can create testcase based on that reproducer later on.
> 
> -- 
> Cyril Hrubis
> chrubis@xxxxxxx

OK, I'll do.

Yury