scripts/gdb: fix debugging modules compiled with hot/cold partitioning

gcc's -freorder-blocks-and-partition option makes it group frequently
and infrequently used code in .text.hot and .text.unlikely sections
respectively.  At least when building modules on s390, this option is
used by default.

gdb assumes that all code is located in .text section, and that .text
section is located at module load address.  With such modules this is no
longer the case: there is code in .text.hot and .text.unlikely, and
either of them might precede .text.

Fix by explicitly telling gdb the addresses of code sections.

It might be tempting to do this for all sections, not only the ones in
the white list.  Unfortunately, gdb appears to have an issue, when
telling it about e.g. loadable .note.gnu.build-id section causes it to
think that non-loadable .note.Linux section is loaded at address 0,
which in turn causes NULL pointers to be resolved to bogus symbols.  So
keep using the white list approach for the time being.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ilya Leoshkevich <[email protected]>
Reviewed-by: Jan Kiszka <[email protected]>
Cc: Kieran Bingham <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

scripts/gdb/linux/symbols.py

@@ -99,7 +99,8 @@ def _section_arguments(self, module):
             attrs[n]['name'].string(): attrs[n]['address']
             for n in range(int(sect_attrs['nsections']))}
         args = []
-        for section_name in [".data", ".data..read_mostly", ".rodata", ".bss"]:
+        for section_name in [".data", ".data..read_mostly", ".rodata", ".bss",
+                             ".text", ".text.hot", ".text.unlikely"]:
             address = section_name_to_address.get(section_name)
             if address:
                 args.append(" -s {name} {addr}".format(