PR 20569, segv in follow_exec
authorSandra Loosemore <sandra@codesourcery.com>
Wed, 26 Oct 2016 17:12:01 +0000 (12:12 -0500)
committerPedro Alves <palves@redhat.com>
Wed, 26 Oct 2016 15:47:46 +0000 (16:47 +0100)
commitecf45d2cc7667ed4692d07e52fc77a2c9a8adf1c
treeabc757e04ab221b35d3d0db5afba7f9f82da645a
parentb15cc25cbe7c13e450f77b4a309223b9b3da3936
PR 20569, segv in follow_exec

The following testcases make GDB crash whenever an invalid sysroot is
provided, when GDB is unable to find a valid path to the symbol file:

 gdb.base/catch-syscall.exp
 gdb.base/execl-update-breakpoints.exp
 gdb.base/foll-exec-mode.exp
 gdb.base/foll-exec.exp
 gdb.base/foll-vfork.exp
 gdb.base/pie-execl.exp
 gdb.multi/bkpt-multi-exec.exp
 gdb.python/py-finish-breakpoint.exp
 gdb.threads/execl.exp
 gdb.threads/non-ldr-exc-1.exp
 gdb.threads/non-ldr-exc-2.exp
 gdb.threads/non-ldr-exc-3.exp
 gdb.threads/non-ldr-exc-4.exp
 gdb.threads/thread-execl.exp

The immediate cause of the segv is that follow_exec is passing a NULL
argument (the result of exec_file_find) to strlen.

However, the problem is deeper than that: follow_exec simply isn't
prepared for the case where sysroot translation fails to locate the
new executable.  Actually all callers of exec_file_find have bugs due
to confusion between host and target pathnames.  This commit attempts
to fix all that.

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.

A new representative test is added which exercises the ne wwarning
code path even with native testing.

Tested on x86_64 Fedora 23, native and gdbserver.

gdb/ChangeLog:
2016-10-25  Sandra Loosemore  <sandra@codesourcery.com>
    Luis Machado  <lgustavo@codesourcery.com>
    Pedro Alves  <palves@redhat.com>

PR gdb/20569
* exceptions.c (exception_print_same): Moved here from exec.c.
* exceptions.h (exception_print_same): Declare.
* exec.h: Include "symfile-add-flags.h".
(try_open_exec_file): New declaration.
* exec.c (exception_print_same): Moved to exceptions.c.
(try_open_exec_file): New function.
(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; Call try_open_exec_file.
* infrun.c (follow_exec): Split and rename execd_pathname variable
to avoid confusion between target and host pathnames.  Warn if
pathname lookup fails.  Pass target pathname to
target_follow_exec, not hostpathname.  Call try_open_exec_file.
* main.c (symbol_file_add_main_adapter): New function.
(captured_main_1): Use it.
* solib-svr4.c (open_symbol_file_object): Adjust to pass
symfile_add_flags to symbol_file_add_main.
* solib.c (exec_file_find): Incorporate fallback logic for relative
pathnames formerly in exec_file_locate_attach.
* symfile.c (symbol_file_add_main, symbol_file_add_main_1):
Replace 'from_tty' parameter with a symfile_add_file.
(symbol_file_command): Adjust to pass symfile_add_flags to
symbol_file_add_main.
* symfile.h (symbol_file_add_main): Replace 'from_tty' parameter
with a symfile_add_file.

gdb/testsuite/ChangeLog:
2016-10-25  Luis Machado  <lgustavo@codesourcery.com>

* gdb.base/exec-invalid-sysroot.exp: New file.
14 files changed:
gdb/ChangeLog
gdb/exceptions.c
gdb/exceptions.h
gdb/exec.c
gdb/exec.h
gdb/inferior.c
gdb/infrun.c
gdb/main.c
gdb/solib-svr4.c
gdb/solib.c
gdb/symfile.c
gdb/symfile.h
gdb/testsuite/ChangeLog
gdb/testsuite/gdb.base/exec-invalid-sysroot.exp [new file with mode: 0644]