[PATCH] target/m68k: implement fmove.l #<data>,FPCR

[Laurent Vivier <laurent@vivier.eu>]

The immediate value mode was ignored and instruction execution
ends to an invalid access mode.

This was found running 'R' that set FPSR to 0 at startup with
a 'fmove.l #0,FPSR' in qemu-system-m68k emulation and triggers a
kernel crash:

[   56.640000] *** ADDRESS ERROR ***   FORMAT=2
[   56.640000] Current process id is 728
[   56.640000] BAD KERNEL TRAP: 00000000
[   56.640000] Modules linked in: sg evdev mac_hid ip_tables x_tables sha1_generic hmac ipv6 nf_defrag_ipv6 autofs4 ext4 crc16 mbcache jbd2 crc32c_generic sd_mod t10_pi crc_t10dif crct10dif_generic crct10dif_common sr_mod cdrom mac_esp macsonic esp_scsi
[   56.640000] PC: [<00016a2c>] X_UNSUPP+0x2c/0x3c
[   56.640000] SR: 2004  SP: 3eb5e68c  a2: c02e239a
[   56.640000] d0: 00000040    d1: 00000002    d2: 8002adec    d3: 8002ad50
[   56.640000] d4: 8002c768    d5: 0000000d    a0: ffffffc2    a1: ffffffc1
[   56.640000] Process R (pid: 728, task=a3dfda5d)
[   56.640000] Frame format=2 instr addr=00000000
[   56.650000] Stack from 3a4d9f30:
[   56.650000]         41000000 00000002 00000002 ffffffc2 ffffffc1 1fff0000 80000000 00000000
[   56.650000]         3fbf0000 80000000 00000000 00000000 20000000 00000000 7fff0000 ffffffff
[   56.650000]         ffffffff 00000000 00050008 00000000 8000067c c02c2000 efffee20 000002d8
[   56.650000]         00002a28 3a4d9f98 00000002 00000014 fffffffe 8002c768 00000002 00000041
[   56.650000]         00000002 c041fc58 c0743758 ffffffff 00000000 0008c075 00002b24 00000012
[   56.650000]         000007d0 00000024 00000002 c05bef04 c05bef04 0000005e 00000077 c28aca70
[   56.650000] Call Trace: [<00050008>] copy_overflow+0x10/0x28
[   56.650000]  [<00002a28>] buserr+0x20/0x28
[   56.650000]  [<0008c075>] bpf_check+0x57f/0x1cfa
[   56.650000]  [<00002b24>] syscall+0x8/0xc
[   56.650000]  [<0000c019>] dn_sched_init+0x75/0x88
[   56.650000] Code: 1017 0200 00f0 0c00 0040 66ff 0000 05ac <f23c> 8800 0000 0000 f23c 9000 0000 0000 222e ff84 082e 0005 ff1c 6600 000a 0281
[   56.650000] Disabling lock debugging due to kernel taint
...

Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 target/m68k/translate.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index 0f80888203d3..c093f6c683e8 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -4936,6 +4936,20 @@ static void gen_op_fmove_fcr(CPUM68KState *env, DisasContext *s,
             gen_store_fcr(s, AREG(insn, 0), mask);
         }
         return;
+    case 7: /* Immediate */
+        if (REG(insn, 0) == 4) {
+            if (is_write ||
+                (mask != M68K_FPIAR && mask != M68K_FPSR &&
+                 mask != M68K_FPCR)) {
+                gen_exception(s, s->base.pc_next, EXCP_ILLEGAL);
+                return;
+            }
+            tmp = tcg_const_i32(read_im32(env, s));
+            gen_store_fcr(s, tmp, mask);
+            tcg_temp_free(tmp);
+            return;
+        }
+        break;
     default:
         break;
     }
-- 
2.26.2