The following one-line-program can reproduce the bug:
main() { asm(" vmul.f32 q0,q1,q2 "); }
Compiling and assembling this code will result in a 'Segmentation fault" caused
by gas. However the seg.fault seems to appear only when assembling directly on
an ARM device (in my case Nokia N900) or within the scratchbox developing
environment as well, here not using the cross-assembler, but an native ARM
version. I compiles gas with configure -target=arm-linux-gnueabi
Using gdb I found the error producing code in file gas/config/tc-arm.c in
function neon_check_type(), line 12055 (version from beginning Jan 2010):
unsigned regwidth = neon_shape_el_size[regshape], match;
Here regshape has a random value causing unpredictable memory access via
neon_shape_el_size[]. One line before regshape is assigned a value from
neon_shape_tab[ns] with ns=40=NS_NULL, but neon_shape_tab[] has 40 entries only
[0..39], thus accessing the 41st entry will return the random value (64 in my
case) for regshape.
The invalid value ns=NS_NULL=40 is passed to neon_check_type() by function
try_vfp_nsyn() which got this wrong value in before from a call to
neon_select_shape(). This function should catch a value of NS_NULL as error
"invalid instruction shape" but somehow does not. Besides from the uncaught
error the code is valid.
--
Summary: segmentaion fault while processing NEON arithmetric
instructions
Product: binutils
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: gas
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: andre dot bergner dot 0 at googlemail dot com
CC: bug-binutils at gnu dot org
GCC build triplet: arm-linux-gnueabi
GCC host triplet: arm-linux-gnueabi
GCC target triplet: arm-linux-gnueabi
http://sourceware.org/bugzilla/show_bug.cgi?id=11136
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