As I noted in PR20569, several exec-related tests cause GDB to segv when
sysroot translation fails on the executable pathname reported by
gdbserver. The immediate cause of the segv is that follow_exec is
passing a NULL argument (the result of exec_file_find) to strlen, but as
I looked at the code in more detail it seemed like follow_exec simply
isn't prepared for the case where sysroot translation fails to locate
the new executable, and there is no obvious recovery strategy.
I thought I could copy logic from the other caller of exec_file_find,
exec_file_locate_attach, but I think it's doing the wrong thing there as
well. Plus, from reading the code I found other bugs in both callers of
exec_file_find due to confusion between host and target pathnames.
The attached patch attempts to fix all the bugs. In terms of the
testcases that were formerly segv'ing, GDB now prints a warning but
continues execution of the new program, so that the tests now mostly
FAIL instead. You could argue the FAILs are due to a legitimate problem
with the test environment setting up the sysroot translation
incorrectly, but I'm not sure continuing execution rather than leaving
the target stopped is the most user-friendly fallback behavior, either.
E.g. the GDB manual suggests that you can set a breakpoint on main and
GDB will stop on main of the newly exec'ed program, too, but it can't do
that if it can't find the symbol information, and there's no way for the
user to specify the executable file to GDB explicitly before it resumes
execution. But, seemed better not to complicate this
already-too-complicated patch further by trying to address that in the
first cut.
Comments? Suggestions? Etc.
-Sandra
gdb-segv2.log
2016-10-06 Sandra Loosemore <sandra@codesourcery.com>
PR gdb/20569
gdb/
* exceptions.c (exception_print_same): Moved here from exec.c.
Fixed message comparison.
* exceptions.h (exception_print_same): Declare.
* exec_file_locate_attach (exception_print_same): Delete copy here.
(exec_file_locate_attach): Rename exec_file and full_exec_path
variables to avoid confusion between target and host pathnames.
Move pathname processing logic to exec_file_find. Do not return
early if pathname lookup fails; guard symbol_file_add_main call
instead.
* infrun.c (follow_exec): Split and rename execd_pathname variable
to avoid confusion between target and host pathnames. Replace
brokenpathname copy with cleanup to free malloc'ed string. Warn
if pathname lookup fails. Pass target pathname to
target_follow_exec, not hostpathname. Borrow exception-handling
logic from exec_file_locate_attach.
* solib.c (exec_file_find): Incorporate fallback logic for relative
pathnames formerly in exec_file_locate_attach.
gdb-segv2.patch