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| author | Tom Tromey <tom@tromey.com> | 2018-04-21 11:51:34 -0600 |
|---|---|---|
| committer | Tom Tromey <tom@tromey.com> | 2018-05-07 08:47:37 -0600 |
| commit | ce887586b48acd02080c36d5495891116f886e8e (patch) | |
| tree | 1e9c2ea9833fbf536b55f56e61de2c4b3ccd0fc3 /gdb/arm-tdep.c | |
| parent | 2ceb7719f763b9e541a379d8ac7d53a72794fdd4 (diff) | |
| download | binutils-gdb-ce887586b48acd02080c36d5495891116f886e8e.tar.gz | |
Fix decoding of ARM VFP instructions
-Wduplicated-cond pointed out that arm_record_vfp_data_proc_insn
checks "opc1 == 0x0b" twice. I filed this a while ago as
PR tdep/20362.
Based on the ARM instruction manual at
https://www.scss.tcd.ie/~waldroj/3d1/arm_arm.pdf, I think the
instruction decoding in this function has two bugs.
First, opc1 is computed as:
opc1 = bits (arm_insn_r->arm_insn, 20, 23);
[...]
opc1 = opc1 & 0x04;
This means that tests like:
else if (opc1 == 0x01)
can never be true.
In the ARM manual, "opc1" corresponds to these bits:
name bit
r 20
q 21
D 22
p 23
... where the D bit is not used for VFP instruction decoding.
So, I believe this code should use ~0x04 instead.
Second, VDIV is recognized by the bits "pqrs" being equal to "1000".
This tranlates to opc1 == 0x08 -- not 0x0b. Note that pqrs==1001 is
an undefined encoding, which is probably why opc2 is not checked here;
this code doesn't seem to really deal with undefined encodings in
general, so I've left that as is.
I don't have an ARM machine or any reasonable way to test this.
ChangeLog
2018-05-07 Tom Tromey <tom@tromey.com>
PR tdep/20362:
* arm-tdep.c (arm_record_vfp_data_proc_insn): Properly mask off D
bit. Use correct value for VDIV.
Diffstat (limited to 'gdb/arm-tdep.c')
| -rw-r--r-- | gdb/arm-tdep.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c index a188f0afcf6..382080a714b 100644 --- a/gdb/arm-tdep.c +++ b/gdb/arm-tdep.c @@ -11421,7 +11421,8 @@ arm_record_vfp_data_proc_insn (insn_decode_record *arm_insn_r) opc3 = bits (arm_insn_r->arm_insn, 6, 7); dp_op_sz = bit (arm_insn_r->arm_insn, 8); bit_d = bit (arm_insn_r->arm_insn, 22); - opc1 = opc1 & 0x04; + /* Mask off the "D" bit. */ + opc1 = opc1 & ~0x04; /* Handle VMLA, VMLS. */ if (opc1 == 0x00) @@ -11486,7 +11487,7 @@ arm_record_vfp_data_proc_insn (insn_decode_record *arm_insn_r) } } /* Handle VDIV. */ - else if (opc1 == 0x0b) + else if (opc1 == 0x08) { if (dp_op_sz) curr_insn_type = INSN_T1; |