can't retrieve backtrace on remote i960 target

[Vadim Bendebury]

Hi, I have gdb 5.2.1 built for mips and i960 remote environments.

The problem is with the gdb `bt' command when connecting to i960
targets (mips works fine).

When the target is stopped, all registers' values (by the fp set) are
correctly reported to the gdb host (target's and host's
representation of the registers are identical).

When trying to retrieve the stack backtrace (entering 'bt' command on
the gdb host), the host just displace the current frame and insists
that this is the top frame (which is definitely not the case).

Looking at the communications between the host and the target: the
host requests to read 4 bytes of memory at address pointed at by the
fp register. The target returns the value read at that memory (in
target byte order), which in fact is the contents of the pfp
register. After that the host's gdb interface reprots that we're at
the top frame.

Any clues would be highly appreciated!

Below is a capture of the communications exchange between the host
and the target:

-------------------- cut here --------------------------------
va:/ 36# snoop -x 42 134.112.29.40
Using device /dev/eri (promiscuous mode)
   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=9

           0: 2b                                         +

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=16

           0: 2448 632d 3123 3039                        $Hc-1#09

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=9

           0: 2b00 0000 0000 0000 0000 0000 0000 0000   
+...............
          16: 0000                                       ..

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=51

           0: 2454 3032 3233 3a36 6332 3630 3031 303b   
$T0223:6c260010;
          16: 3031 3a36 3031 6231 3931 303b 3166 3a62   
01:601b1910;1f:b
          32: 3031 6231 3931 303b 2365 38                01b1910;#e8

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=9

           0: 2b                                         +

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=14

           0: 2471 4323 6234                             $qC#b4

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=9

           0: 2b00 0000 0000 0000 0000 0000 0000 0000   
+...............
          16: 0000                                       ..

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=12

           0: 2423 3030 3233 3a36 6332 3630 3031 303b   
$#0023:6c260010;
          16: 3031                                       01

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=9

           0: 2b                                         +

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=20

           0: 2471 4f66 6673 6574 7323 3462              $qOffsets#4b

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=9

           0: 2b00 0000 0000 0000 0000 0000 0000 0000   
+...............
          16: 0000                                       ..

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=12

           0: 2423 3030 3233 3a36 6332 3630 3031 303b   
$#0023:6c260010;
          16: 3031                                       01

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=9

           0: 2b                                         +

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=13

           0: 243f 2333 66                               $?#3f

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=9

           0: 2b00 0000 0000 0000 0000 0000 0000 0000   
+...............
          16: 0000                                       ..

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=51

           0: 2454 3032 3233 3a36 6332 3630 3031 303b   
$T0223:6c260010;
          16: 3031 3a36 3031 6231 3931 303b 3166 3a62   
01:601b1910;1f:b
          32: 3031 6231 3931 303b 2365 38                01b1910;#e8

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=9

           0: 2b                                         +

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=23

           0: 246d 3130 3139 3162 6230 2c34 2362 64     
$m10191bb0,4#bd

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=9

           0: 2b00 0000 0000 0000 0000 0000 0000 0000   
+...............
          16: 0000                                       ..

134.112.29.40 -> vadim-sun    UDP D=49785 S=10117 LEN=20

           0: 2465 3031 6131 3931 3023 6632 3031 303b   
$e01a1910#f2010;
          16: 3031                                       01

   vadim-sun -> 134.112.29.40 UDP D=10117 S=49785 LEN=9

           0: 2b                                         +


---------------- cut here ------------------------------
Regards,
Vadim Bendebury

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