[Bug remote/23893] New: Search paths for debug files for remote debuggee checks are broken

[autkin at undo dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=23893

Bug ID: 23893
Summary: Search paths for debug files for remote debuggee
checks are broken
Product: gdb
Version: HEAD
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: remote
Assignee: unassigned at sourceware dot org
Reporter: autkin at undo dot io
Target Milestone: ---

Created attachment 11401
--> https://sourceware.org/bugzilla/attachment.cgi?id=11401&action=edit
proposed patch

Originally submitted just as a patch:
https://sourceware.org/ml/gdb-patches/2018-11/msg00168.html

When using remote debugging server, and when debuggee filename is
inferred via qXfer:exec-file:read request, or sysroot starts with
"target:", this "target:" prefix of filepaths is not treated correctly
during debug file search - it appears in the middle of the looked up
paths.

In the following example, unpatched GDB can't find separate debug files for
neither the executable, nor standard libraries:

$ gdb -ex 'set debug separate-debug-file 1' -ex 'set sysroot target:/' -ex
'set debug-file-directory /usr/lib/debug:/home/j/hide' -ex 'target remote
:3333' -ex 'break main' -ex 'continue' -ex 'bt' -ex 'info sharedlibrary' -ex
'set confirm off' -ex 'quit'
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Remote debugging using :3333
Reading /home/j/test from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot"
to access files locally instead.
Reading /home/j/test from remote target...
Reading symbols from target:/home/j/test...

Looking for separate debug info (debug link) for target:/home/j/test
Trying target:/home/j/test.debug
Reading /home/j/test.debug from remote target...
Trying target:/home/j/.debug/test.debug
Reading /home/j/.debug/test.debug from remote target...
Trying /usr/lib/debug/target:/home/j/test.debug
Trying /home/j/hide/target:/home/j/test.debug
(No debugging symbols found in target:/home/j/test)
Reading /lib64/ld-linux-x86-64.so.2 from remote target...
Reading /lib64/ld-linux-x86-64.so.2 from remote target...
Reading symbols from target:/lib64/ld-linux-x86-64.so.2...

Looking for separate debug info (debug link) for
target:/lib64/ld-linux-x86-64.so.2
Trying target:/lib64/ld-2.27.so.debug
Reading /lib64/ld-2.27.so.debug from remote target...
Trying target:/lib64/.debug/ld-2.27.so.debug
Reading /lib64/.debug/ld-2.27.so.debug from remote target...
Trying /usr/lib/debug/target:/lib64/ld-2.27.so.debug
Trying /home/j/hide/target:/lib64/ld-2.27.so.debug
(No debugging symbols found in target:/lib64/ld-linux-x86-64.so.2)

Looking for separate debug info (build-id) for system-supplied DSO at
0x7ffff7ffa000
Trying
/usr/lib/debug/.build-id/fd/03d584bc1a90ba28be457635a02662c9f9c1f2.debug
Trying
/home/j/hide/.build-id/fd/03d584bc1a90ba28be457635a02662c9f9c1f2.debug
0x00007ffff7dd7000 in ?? () from target:/lib64/ld-linux-x86-64.so.2
Breakpoint 1 at 0x4005eb
Continuing.
Reading /lib64/libpthread.so.0 from remote target...
Reading /lib64/libc.so.6 from remote target...

Looking for separate debug info (debug link) for
target:/lib64/libpthread.so.0
Trying target:/lib64/libpthread-2.27.so.debug
Reading /lib64/libpthread-2.27.so.debug from remote target...
Trying target:/lib64/.debug/libpthread-2.27.so.debug
Reading /lib64/.debug/libpthread-2.27.so.debug from remote target...
Trying /usr/lib/debug/target:/lib64/libpthread-2.27.so.debug
Trying /home/j/hide/target:/lib64/libpthread-2.27.so.debug

Looking for separate debug info (debug link) for target:/lib64/libc.so.6
Trying target:/lib64/libc-2.27.so.debug
Reading /lib64/libc-2.27.so.debug from remote target...
Trying target:/lib64/.debug/libc-2.27.so.debug
Reading /lib64/.debug/libc-2.27.so.debug from remote target...
Trying /usr/lib/debug/target:/lib64/libc-2.27.so.debug
Trying /home/j/hide/target:/lib64/libc-2.27.so.debug

Breakpoint 1, 0x00000000004005eb in main ()
#0 0x00000000004005eb in main ()
From To Syms Read Shared Object Library
0x00007ffff7dd6e80 0x00007ffff7df4650 Yes (*)
target:/lib64/ld-linux-x86-64.so.2
0x00007ffff7bbbb70 0x00007ffff7bcbfee Yes (*)
target:/lib64/libpthread.so.0
0x00007ffff780f200 0x00007ffff7962d7c Yes (*) target:/lib64/libc.so.6
(*): Shared library is missing debugging information.

With the proposed fix (see patch attached), the paths used always have target:
in the beginning and this helps to find all debug files.