diff options
author | Peter Maydell <peter.maydell@linaro.org> | 2021-09-01 15:10:08 +0100 |
---|---|---|
committer | Peter Maydell <peter.maydell@linaro.org> | 2021-12-15 10:35:26 +0000 |
commit | e0e875a68a1cc699658a40b8449267c7460de60f (patch) | |
tree | 16ad4244076077ee3bd25675aff0ae0e5b4ef14c /target/i386/tcg | |
parent | 0bdce4861f924a5efd5c57a7a40f2d8a4269fa80 (diff) | |
download | qemu-e0e875a68a1cc699658a40b8449267c7460de60f.zip qemu-e0e875a68a1cc699658a40b8449267c7460de60f.tar.gz qemu-e0e875a68a1cc699658a40b8449267c7460de60f.tar.bz2 |
target/i386: Use assert() to sanity-check b1 in SSE decode
In the SSE decode function gen_sse(), we combine a byte
'b' and a value 'b1' which can be [0..3], and switch on them:
b |= (b1 << 8);
switch (b) {
...
default:
unknown_op:
gen_unknown_opcode(env, s);
return;
}
In three cases inside this switch, we were then also checking for
"if (b1 >= 2) { goto unknown_op; }".
However, this can never happen, because the 'case' values in each place
are 0x0nn or 0x1nn and the switch will have directed the b1 == (2, 3)
cases to the default already.
This check was added in commit c045af25a52e9 in 2010; the added code
was unnecessary then as well, and was apparently intended only to
ensure that we never accidentally ended up indexing off the end
of an sse_op_table with only 2 entries as a result of future bugs
in the decode logic.
Change the checks to assert() instead, and make sure they're always
immediately before the array access they are protecting.
Fixes: Coverity CID 1460207
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'target/i386/tcg')
-rw-r--r-- | target/i386/tcg/translate.c | 12 |
1 files changed, 3 insertions, 9 deletions
diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c index e9e1451..05f9336 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -3519,9 +3519,6 @@ static void gen_sse(CPUX86State *env, DisasContext *s, int b, case 0x171: /* shift xmm, im */ case 0x172: case 0x173: - if (b1 >= 2) { - goto unknown_op; - } val = x86_ldub_code(env, s); if (is_xmm) { tcg_gen_movi_tl(s->T0, val); @@ -3540,6 +3537,7 @@ static void gen_sse(CPUX86State *env, DisasContext *s, int b, offsetof(CPUX86State, mmx_t0.MMX_L(1))); op1_offset = offsetof(CPUX86State,mmx_t0); } + assert(b1 < 2); sse_fn_epp = sse_op_table2[((b - 1) & 3) * 8 + (((modrm >> 3)) & 7)][b1]; if (!sse_fn_epp) { @@ -3770,10 +3768,8 @@ static void gen_sse(CPUX86State *env, DisasContext *s, int b, rm = modrm & 7; reg = ((modrm >> 3) & 7) | REX_R(s); mod = (modrm >> 6) & 3; - if (b1 >= 2) { - goto unknown_op; - } + assert(b1 < 2); sse_fn_epp = sse_op_table6[b].op[b1]; if (!sse_fn_epp) { goto unknown_op; @@ -4200,10 +4196,8 @@ static void gen_sse(CPUX86State *env, DisasContext *s, int b, rm = modrm & 7; reg = ((modrm >> 3) & 7) | REX_R(s); mod = (modrm >> 6) & 3; - if (b1 >= 2) { - goto unknown_op; - } + assert(b1 < 2); sse_fn_eppi = sse_op_table7[b].op[b1]; if (!sse_fn_eppi) { goto unknown_op; |