@@ -50,13 +50,27 @@ static int tszimm_esz(DisasContext *s, int x)
static int tszimm_shr(DisasContext *s, int x)
{
- return (16 << tszimm_esz(s, x)) - x;
+ /*
+ * We won't use the tszimm_shr() value if tszimm_esz() returns -1 (the
+ * trans function will check for esz < 0), so we can return any
+ * value we like from here in that case as long as we avoid UB.
+ */
+ int esz = tszimm_esz(s, x);
+ if (esz < 0) {
+ return esz;
+ }
+ return (16 << esz) - x;
}
/* See e.g. LSL (immediate, predicated). */
static int tszimm_shl(DisasContext *s, int x)
{
- return x - (8 << tszimm_esz(s, x));
+ /* As with tszimm_shr(), value will be unused if esz < 0 */
+ int esz = tszimm_esz(s, x);
+ if (esz < 0) {
+ return esz;
+ }
+ return x - (8 << esz);
}
/* The SH bit is in bit 8. Extract the low 8 and shift. */
The function tszimm_esz() returns a shift amount, or possibly -1 in certain cases that correspond to unallocated encodings in the instruction set. We catch these later in the trans_ functions (generally with an "a-esz < 0" check), but before we do the decodetree-generated code will also call tszimm_shr() or tszimm_sl(), which will use the tszimm_esz() return value as a shift count without checking that it is not negative, which is undefined behaviour. Avoid the UB by checking the return value in tszimm_shr() and tszimm_shl(). Cc: qemu-stable@nongnu.org Resolves: Coverity CID 1547617, 1547694 Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- target/arm/tcg/translate-sve.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)