<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/135839>135839</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
[LLDB] MIPS has missing aliases for register
</td>
</tr>
<tr>
<th>Labels</th>
<td>
new issue
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
patryk4815
</td>
</tr>
</table>
<pre>
Same bug as in:
- https://github.com/llvm/llvm-project/issues/123903
- https://github.com/llvm/llvm-project/issues/124023
When debugging with gdbserver, some registers lack their "standard" aliases.
(btw qemu-mips don't work - I don't know why, probably qemu issue)
Steps to reproduction:
My small openwrt TP-LINK Switch with ~18MB disk space:
```
root@OpenWrt:/tmp# ./gdbserver 0:1234 /bin/sh
Process /bin/sh created; pid = 4445
Listening on port 1234
```
(not possible to build lldb-server, to fit there)
My host:
```
(lldb) file ./sh
Current executable set to '/tmp/dd/sh' (mipsr2).
(lldb) log enable gdb-remote all
(lldb) gdb-remote 192.168.1.1:1234
Process 4445 stopped
* thread #1, stop reason = signal SIGTRAP
frame #0: 0x77f3abc0
-> 0x77f3abc0: bal 0x77f3abd4
0x77f3abc4: move $fp, $zero
(lldb)
(lldb) register read k0
error: Invalid register name 'k0'.
(lldb) register read a0
error: Invalid register name 'a0'.
(lldb) register read v0
error: Invalid register name 'v0'.
```
Gdb protocol:
```
.lldb-wrapped < 42> send packet: $qXfer:features:read:target.xml:0,2001e#73
.lldb-wrapped < 618> read packet: $l<?xml version="1.0"?>
<!-- Copyright (C) 2007-2024 Free Software Foundation, Inc.
*!Copying and distribution of this file, with or without modification,
*!are permitted in any medium without royalty provided the copyright
*!notice and this notice are preserved. -->
<!DOCTYPE target SYSTEM "gdb-target.dtd">
<target>
<architecture>mips</architecture>
<osabi>GNU/Linux</osabi>
<xi:include href="mips-cpu.xml"/>
<xi:include href="mips-cp0.xml"/>
<xi:include href="mips-fpu.xml"/>
<feature name="org.gnu.gdb.mips.linux">
* <reg name="restart" bitsize="32" group="system"/>
</feature>
</target>
#de
.lldb-wrapped < 44> send packet: $qXfer:features:read:mips-cpu.xml:0,2001e#1a
.lldb-wrapped <1559> read packet: $l<?xml version="1.0"?>
<!-- Copyright (C) 2007-2024 Free Software Foundation, Inc.
*!Copying and distribution of this file, with or without modification,
*!are permitted in any medium without royalty provided the copyright
*!notice and this notice are preserved. -->
<!DOCTYPE feature SYSTEM "gdb-target.dtd">
<feature name="org.gnu.gdb.mips.cpu">
<reg name="r0" bitsize="32" regnum="0"/>
<reg name="r1" bitsize="32"/>
<reg name="r2" bitsize="32"/>
<reg name="r3" bitsize="32"/>
<reg name="r4" bitsize="32"/>
<reg name="r5" bitsize="32"/>
<reg name="r6" bitsize="32"/>
<reg name="r7" bitsize="32"/>
<reg name="r8" bitsize="32"/>
<reg name="r9" bitsize="32"/>
<reg name="r10" bitsize="32"/>
<reg name="r11" bitsize="32"/>
<reg name="r12" bitsize="32"/>
<reg name="r13" bitsize="32"/>
<reg name="r14" bitsize="32"/>
<reg name="r15" bitsize="32"/>
<reg name="r16" bitsize="32"/>
<reg name="r17" bitsize="32"/>
<reg name="r18" bitsize="32"/>
<reg name="r19" bitsize="32"/>
<reg name="r20" bitsize="32"/>
<reg name="r21" bitsize="32"/>
<reg name="r22" bitsize="32"/>
<reg name="r23" bitsize="32"/>
<reg name="r24" bitsize="32"/>
<reg name="r25" bitsize="32"/>
<reg name="r26" bitsize="32"/>
<reg name="r27" bitsize="32"/>
<reg name="r28" bitsize="32"/>
<reg name="r29" bitsize="32"/>
<reg name="r30" bitsize="32"/>
<reg name="r31" bitsize="32"/>
<reg name="lo" bitsize="32" regnum="33"/>
<reg name="hi" bitsize="32" regnum="34"/>
<reg name="pc" bitsize="32" regnum="37"/>
</feature>
#9d
.lldb-wrapped < 44> send packet: $qXfer:features:read:mips-cp0.xml:0,2001e#d5
.lldb-wrapped < 514> read packet: $l<?xml version="1.0"?>
<!-- Copyright (C) 2007-2024 Free Software Foundation, Inc.
*!Copying and distribution of this file, with or without modification,
*!are permitted in any medium without royalty provided the copyright
*!notice and this notice are preserved. -->
<!DOCTYPE feature SYSTEM "gdb-target.dtd">
<feature name="org.gnu.gdb.mips.cp0">
<reg name="status" bitsize="32" regnum="32"/>
<reg name="badvaddr" bitsize="32" regnum="35"/>
<reg name="cause" bitsize="32" regnum="36"/>
</feature>
#f0
.lldb-wrapped < 44> send packet: $qXfer:features:read:mips-fpu.xml:0,2001e#1d
.lldb-wrapped <2131> read packet: $l<?xml version="1.0"?>
<!-- Copyright (C) 2007-2024 Free Software Foundation, Inc.
*!Copying and distribution of this file, with or without modification,
*!are permitted in any medium without royalty provided the copyright
*!notice and this notice are preserved. -->
<!DOCTYPE feature SYSTEM "gdb-target.dtd">
<feature name="org.gnu.gdb.mips.fpu">
<reg name="f0" bitsize="32" type="ieee_single" regnum="38"/>
<reg name="f1" bitsize="32" type="ieee_single"/>
<reg name="f2" bitsize="32" type="ieee_single"/>
<reg name="f3" bitsize="32" type="ieee_single"/>
<reg name="f4" bitsize="32" type="ieee_single"/>
<reg name="f5" bitsize="32" type="ieee_single"/>
<reg name="f6" bitsize="32" type="ieee_single"/>
<reg name="f7" bitsize="32" type="ieee_single"/>
<reg name="f8" bitsize="32" type="ieee_single"/>
<reg name="f9" bitsize="32" type="ieee_single"/>
<reg name="f10" bitsize="32" type="ieee_single"/>
<reg name="f11" bitsize="32" type="ieee_single"/>
<reg name="f12" bitsize="32" type="ieee_single"/>
<reg name="f13" bitsize="32" type="ieee_single"/>
<reg name="f14" bitsize="32" type="ieee_single"/>
<reg name="f15" bitsize="32" type="ieee_single"/>
<reg name="f16" bitsize="32" type="ieee_single"/>
<reg name="f17" bitsize="32" type="ieee_single"/>
<reg name="f18" bitsize="32" type="ieee_single"/>
<reg name="f19" bitsize="32" type="ieee_single"/>
<reg name="f20" bitsize="32" type="ieee_single"/>
<reg name="f21" bitsize="32" type="ieee_single"/>
<reg name="f22" bitsize="32" type="ieee_single"/>
<reg name="f23" bitsize="32" type="ieee_single"/>
<reg name="f24" bitsize="32" type="ieee_single"/>
<reg name="f25" bitsize="32" type="ieee_single"/>
<reg name="f26" bitsize="32" type="ieee_single"/>
<reg name="f27" bitsize="32" type="ieee_single"/>
<reg name="f28" bitsize="32" type="ieee_single"/>
<reg name="f29" bitsize="32" type="ieee_single"/>
<reg name="f30" bitsize="32" type="ieee_single"/>
<reg name="f31" bitsize="32" type="ieee_single"/>
<reg name="fcsr" bitsize="32" group="float"/>
<reg name="fir" bitsize="32" group="float"/>
</feature>
#dc
```
Not sure if it is good source: https://mathcs.holycross.edu/~csci226/MIPS/summaryHO.pdf
But I follows this register aliases.
<img width="877" alt="Image" src="https://github.com/user-attachments/assets/22763d91-de79-4e22-81ae-e7c9351f3be6" />
</pre>
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