The documentation states that if LSB MSB in BFI instruction behaviour
is unpredictable. Currently QEMU crashes because of assertion failure in
this case:
tcg/tcg-op.h:2061: tcg_gen_deposit_i32: Assertion `len = 32' failed.
While assertion failure may meet the unpredictable definition this
behaviour is undesirable because it allows an unprivileged guest program
to crash the emulator with the OS and other programs.
This patch addresses the issue by throwing illegal instruction exception
if LSB MSB. Only ARM decoder is affected because Thumb decoder already
has this check in place.
To reproduce issue run the following program
int main(void) {
asm volatile (.long 0x07c00c12 :: );
return 0;
}
compiled with
gcc -marm -static badop_arm.c -o badop_arm
Signed-off-by: Kirill Batuzov batuz...@ispras.ru
---
target-arm/translate.c |4
1 file changed, 4 insertions(+)
diff --git a/target-arm/translate.c b/target-arm/translate.c
index bdfcdf1..2c1c2a7 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -8739,6 +8739,10 @@ static void disas_arm_insn(DisasContext *s, unsigned int
insn)
ARCH(6T2);
shift = (insn 7) 0x1f;
i = (insn 16) 0x1f;
+if (i shift) {
+/* UNPREDICTABLE; we choose to UNDEF */
+goto illegal_op;
+}
i = i + 1 - shift;
if (rm == 15) {
tmp = tcg_temp_new_i32();
--
1.7.10.4
