[Qemu-devel] [PULL 03/12] target/arm: Fix vector operation segfault

[Peter Maydell <peter.maydell@linaro.org>]

From: Alistair Francis <alistair.francis@wdc.com>

Commit 89e68b575 "target/arm: Use vector operations for saturation"
causes this abort() when booting QEMU ARM with a Cortex-A15:

0  0x00007ffff4c2382f in raise () at /usr/lib/libc.so.6
1  0x00007ffff4c0e672 in abort () at /usr/lib/libc.so.6
2  0x00005555559c1839 in disas_neon_data_insn (insn=<optimized out>, s=<optimized out>) at ./target/arm/translate.c:6673
3  0x00005555559c1839 in disas_neon_data_insn (s=<optimized out>, insn=<optimized out>) at ./target/arm/translate.c:6386
4  0x00005555559cd8a4 in disas_arm_insn (insn=4081107068, s=0x7fffe59a9510) at ./target/arm/translate.c:9289
5  0x00005555559cd8a4 in arm_tr_translate_insn (dcbase=0x7fffe59a9510, cpu=<optimized out>) at ./target/arm/translate.c:13612
6  0x00005555558d1d39 in translator_loop (ops=0x5555561cc580 <arm_translator_ops>, db=0x7fffe59a9510, cpu=0x55555686a2f0, tb=<optimized out>, max_insns=<optimized out>) at ./accel/tcg/translator.c:96
7  0x00005555559d10d4 in gen_intermediate_code (cpu=cpu@entry=0x55555686a2f0, tb=tb@entry=0x7fffd7840080 <code_gen_buffer+126091347>, max_insns=max_insns@entry=512) at ./target/arm/translate.c:13901
8  0x00005555558d06b9 in tb_gen_code (cpu=cpu@entry=0x55555686a2f0, pc=3067096216, cs_base=0, flags=192, cflags=-16252928, cflags@entry=524288) at ./accel/tcg/translate-all.c:1736
9  0x00005555558ce467 in tb_find (cf_mask=524288, tb_exit=1, last_tb=0x7fffd783e640 <code_gen_buffer+126084627>, cpu=0x1) at ./accel/tcg/cpu-exec.c:407
10 0x00005555558ce467 in cpu_exec (cpu=cpu@entry=0x55555686a2f0) at ./accel/tcg/cpu-exec.c:728
11 0x000055555588b0cf in tcg_cpu_exec (cpu=0x55555686a2f0) at ./cpus.c:1431
12 0x000055555588d223 in qemu_tcg_cpu_thread_fn (arg=0x55555686a2f0) at ./cpus.c:1735
13 0x000055555588d223 in qemu_tcg_cpu_thread_fn (arg=arg@entry=0x55555686a2f0) at ./cpus.c:1709
14 0x0000555555d2629a in qemu_thread_start (args=<optimized out>) at ./util/qemu-thread-posix.c:502
15 0x00007ffff4db8a92 in start_thread () at /usr/lib/libpthread.

This patch ensures that we don't hit the abort() in the second switch
case in disas_neon_data_insn() as we will return from the first case.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: ad91b397f360b2fc7f4087e476f7df5b04d42ddb.1558021877.git.alistair.francis@wdc.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/translate.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/arm/translate.c b/target/arm/translate.c
index dd053c80d62..298c262825d 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -6598,13 +6598,13 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
             tcg_gen_gvec_4(rd_ofs, offsetof(CPUARMState, vfp.qc),
                            rn_ofs, rm_ofs, vec_size, vec_size,
                            (u ? uqadd_op : sqadd_op) + size);
-            break;
+            return 0;
 
         case NEON_3R_VQSUB:
             tcg_gen_gvec_4(rd_ofs, offsetof(CPUARMState, vfp.qc),
                            rn_ofs, rm_ofs, vec_size, vec_size,
                            (u ? uqsub_op : sqsub_op) + size);
-            break;
+            return 0;
 
         case NEON_3R_VMUL: /* VMUL */
             if (u) {
-- 
2.20.1