gdb 8.3.1 truncated register in remote g packet

Reinoud Koornstra reinoudkoornstra@gmail.com
Mon Nov 4 17:53:00 GMT 2019


>
>
> You might have gotten lucky. Or GDB wasn't too restrictive on the checks.
>

True

>
> >
> >     Just to confirm, does your arm target have floating point registers?
> >
> > Good point, I did assume it has, because in some cases armeabihf was
> > used to compile, but not in all cases, I'll check whether it is,
> > otherwise I'd have to recompile gdb without hf.
> > I'll get the info and let you know, thanks for helping out!
>

Yes, the arm cpu used has floating point registers


Well, it seems GDB assumes floating point registers are there by
> default, so there wouldn't be a need to build GDB specifically for that.
>

I did compile a gdb 7.7.1,  i compiled earlier 7.0 (failed to compile
without removing Werror in bfd directory Makefile...), then I tried 7.4.1,
but both of these versions didn't support remote baud rate. However 7.7.1
worked nicely, well way better: (I did go echo g > /proc/sysrq-trigger to
get it waiting for gdb).
GNU gdb (GDB) 7.7.1
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>
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--target=arm-linux-gnueabihf".
Type "show configuration" for configuration details.
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Reading symbols from ./vmlinux...done.
(gdb) set serial baud 115200
(gdb) set debug remote 1
(gdb) target remote /dev/ttyUSB4
Remote debugging using /dev/ttyUSB4
Sending packet: $qSupported:multiprocess+;qRelocInsn+#2a...Ack
Packet received:
Packet qSupported (supported-packets) is NOT supported
Sending packet: $Hg0#df...Ack
Packet received: OK
Sending packet: $qTStatus#49...Ack
Packet received:
Packet qTStatus (trace-status) is NOT supported
Sending packet: $?#3f...Ack
Packet received: S05
Sending packet: $Hc-1#09...Ack
Packet received: OK
Sending packet: $qC#b4...Ack
Packet received: QC1fbb
Sending packet: $qAttached#8f...Ack
Packet received:
Packet qAttached (query-attached) is NOT supported
Sending packet: $qOffsets#4b...Ack
Packet received:
Sending packet: $g#67...Ack
Packet received:
0000000001000000b0829e80ac829e8054829880b4a698806700000013000060060000000000000000000000cc5e0bbfd05e0bbfc05e0bbf10200a80581f0a8000000000000000000000000000000000000000000000000000000000000000000000000000000000
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
Sending packet: $m800a1f54,4#c6...Ack
Packet received: 4ef07ff5
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
Sending packet: $m800a1f54,4#c6...Ack
Packet received: 4ef07ff5
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
Sending packet: $m800a1f54,4#c6...Ack
Packet received: 4ef07ff5
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
Sending packet: $m800a1f54,4#c6...Ack
Packet received: 4ef07ff5
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
Sending packet: $m800a1f58,4#ca...Ack
Packet received: ffdeffe7
0x800a1f58 in arch_kgdb_breakpoint () at kernel/debug/debug_core.c:1049
1049    kernel/debug/debug_core.c: No such file or directory.
Sending packet: $qSymbol::#5b...Ack
Packet received:
Packet qSymbol (symbol-lookup) is NOT supported
(gdb) set debug remote 0
(gdb) bt full
#0  0x800a1f58 in arch_kgdb_breakpoint () at kernel/debug/debug_core.c:1049
No locals.
#1  kgdb_breakpoint () at kernel/debug/debug_core.c:1050
No locals.
#2  0x800a2010 in sysrq_handle_dbg (key=0) at kernel/debug/debug_core.c:810
No locals.
#3  0x80367308 in __handle_sysrq (key=103, check_mask=false) at
drivers/tty/sysrq.c:535
        op_p = 0x8098a6b4 <sysrq_dbg_op>
        orig_log_level = 6
        i = -2137479500
        flags = 1610612755
#4  0x8036745c in write_sysrq_trigger (file=0x0 <__vectors_start>, buf=0x1
<__vectors_start> <error: Cannot access memory at address 0x1>, count=2,
ppos=0x809e82ac <kgdb_use_con>) at drivers/tty/sysrq.c:1083
No locals.
#5  0x80177e18 in proc_reg_write (file=0x0 <__vectors_start>, buf=0x1
<__vectors_start> <error: Cannot access memory at address 0x1>,
count=2157871792, ppos=0xbf0b5f78) at fs/proc/inode.c:224
        write = 0xbf0b5ed0
        rv = 0
#6  0x8011fba4 in vfs_write (file=0xbe37bcc0, buf=0xaa408
"g\nyS0,115200\n", '\337' <repeats 186 times>, <incomplete sequence
\337>..., count=2157871792, pos=0xbf0b5f78) at fs/read_write.c:485
No locals.
#7  0x801201d4 in SYSC_write (count=<optimized out>, buf=<optimized out>,
fd=<optimized out>) at fs/read_write.c:534
        pos = 0
#8  SyS_write (fd=0, buf=697352, count=2) at fs/read_write.c:526
        ret = 0
#9  0x8000f760 in ?? ()
No symbol table info available.
Backtrace stopped: previous frame identical to this frame (corrupt stack?)



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