From cbd2b4e316370ab740433b06ed65786831232c8f Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Mon, 9 Oct 2017 18:11:01 +0100 Subject: [PATCH] Multi-arch exec, more register reading avoidance As mentioned in commit bf93d7ba9931 ("Add thread after updating gdbarch when exec'ing"), we should avoid doing register reads after a process does an exec and before we've updated that inferior's gdbarch. Otherwise, we may interpret the registers using the wrong architecture. There's still (at least) one case where we still read registers post-exec with the pre-exec architecture. That's when infrun decides it needs to switch context to the exec'ing thread. I.e., if the exec event is processed at a time when the current thread is not already the exec'ing thread, then we get (with the test added by this commit): continue Continuing. Truncated register 50 in remote 'g' packet Truncated register 50 in remote 'g' packet (gdb) FAIL: gdb.multi/multi-arch-exec.exp: selected_thread=2: follow_exec_mode=same: continue across exec that changes architecture The fix is to avoid reading registers when switching context in this case. (I'd be nice to get rid of the constant stop_pc reading when switching threads, but that'd be a deeper change.) gdb/ChangeLog: 2017-10-09 Pedro Alves * infrun.c (handle_inferior_event_1) : Skip reading registers when switching context. gdb/testsuite/ChangeLog: 2017-10-09 Pedro Alves * gdb.multi/multi-arch-exec.c: Include and . (barrier): New. (thread_start, all_started): New functions. (main): Spawn new thread and wait until it is scheduled. * gdb.multi/multi-arch-exec.exp: Build $srcfile1 with the pthreads option. (do_test): Add 'selected_thread' parameter. Run to all_started instead of main. Explicitly set the breakpoint at main. Switch to the SELECTED_THREAD thread. (top level): Test handling the exec event with either the main thread or the second thread selected. --- gdb/ChangeLog | 5 ++++ gdb/infrun.c | 5 +++- gdb/testsuite/ChangeLog | 14 ++++++++++ gdb/testsuite/gdb.multi/multi-arch-exec.c | 27 +++++++++++++++++++ gdb/testsuite/gdb.multi/multi-arch-exec.exp | 30 ++++++++++++++++----- 5 files changed, 73 insertions(+), 8 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index b04da8bd443..f1fd73ce201 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2017-10-09 Pedro Alves + + * infrun.c (handle_inferior_event_1) : Skip + reading registers when switching context. + 2017-10-09 John Baldwin * fbsd-nat.c (fbsd_siginfo_size): Use gdbarch_long_bit. diff --git a/gdb/infrun.c b/gdb/infrun.c index e82f61f079f..113add6fed4 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -5307,8 +5307,11 @@ Cannot fill $_exitsignal with the correct signal number.\n")); if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_EXECD\n"); + /* Note we can't read registers yet (the stop_pc), because we + don't yet know the inferior's post-exec architecture. + 'stop_pc' is explicitly read below instead. */ if (!ptid_equal (ecs->ptid, inferior_ptid)) - context_switch (ecs->ptid); + switch_to_thread_no_regs (ecs->event_thread); /* Do whatever is necessary to the parent branch of the vfork. */ handle_vfork_child_exec_or_exit (1); diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index bb62d222ba5..e7b63ff2abc 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,17 @@ +2017-10-09 Pedro Alves + + * gdb.multi/multi-arch-exec.c: Include and . + (barrier): New. + (thread_start, all_started): New functions. + (main): Spawn new thread and wait until it is scheduled. + * gdb.multi/multi-arch-exec.exp: Build $srcfile1 with the pthreads + option. + (do_test): Add 'selected_thread' parameter. Run to all_started + instead of main. Explicitly set the breakpoint at main. Switch + to the SELECTED_THREAD thread. + (top level): Test handling the exec event with either the main + thread or the second thread selected. + 2017-10-09 Pedro Alves * gdb.base/print-file-var-main.c: Fix get_version_2 value check diff --git a/gdb/testsuite/gdb.multi/multi-arch-exec.c b/gdb/testsuite/gdb.multi/multi-arch-exec.c index 1a443dee7bf..f43a5a8b6a7 100644 --- a/gdb/testsuite/gdb.multi/multi-arch-exec.c +++ b/gdb/testsuite/gdb.multi/multi-arch-exec.c @@ -20,11 +20,32 @@ #include #include #include +#include + +#define NUM_THREADS 1 + +static pthread_barrier_t barrier; + +static void * +thread_start (void *arg) +{ + pthread_barrier_wait (&barrier); + + while (1) + sleep (1); + return NULL; +} + +static void +all_started (void) +{ +} int main (int argc, char ** argv) { char prog[PATH_MAX]; + pthread_t thread; int len; strcpy (prog, argv[0]); @@ -33,6 +54,12 @@ main (int argc, char ** argv) memcpy (prog + len - 15, "multi-arch-exec-hello", 21); prog[len + 6] = 0; + pthread_barrier_init (&barrier, NULL, NUM_THREADS + 1); + pthread_create (&thread, NULL, thread_start, NULL); + + pthread_barrier_wait (&barrier); + all_started (); + execl (prog, prog, (char *) NULL); diff --git a/gdb/testsuite/gdb.multi/multi-arch-exec.exp b/gdb/testsuite/gdb.multi/multi-arch-exec.exp index 27a0d602a12..3196cf3f3ad 100644 --- a/gdb/testsuite/gdb.multi/multi-arch-exec.exp +++ b/gdb/testsuite/gdb.multi/multi-arch-exec.exp @@ -53,7 +53,7 @@ if [istarget "s390*-*-*"] { } if { [prepare_for_testing "failed to prepare" ${exec1} "${srcfile1}" \ - [list debug \ + [list debug pthreads \ additional_flags=${march1}]] } { return -1 } @@ -76,22 +76,38 @@ if { [prepare_for_testing "failed to prepare" ${exec2} "${srcfile2}" \ return -1 } -proc do_test { mode } { +proc do_test { mode selected_thread } { global exec1 clean_restart ${exec1} - if ![runto_main] then { - fail "couldn't run to main" + if ![runto all_started] then { + fail "couldn't run to all_started" return -1 } + # Delete the breakpoint at 'all_started' otherwise GDB may + # switch context back to thread 1 to step over the breakpoint. + delete_breakpoints + + # A location for this breakpoint should be found in the new + # post-exec image too. + gdb_breakpoint main + + gdb_test "thread $selected_thread" "Switching to thread $selected_thread .*" + gdb_test_no_output "set follow-exec-mode $mode" # Test that GDB updates the target description / arch successfuly # after the exec. - gdb_test "continue" "Breakpoint 1, main.*" "continue across exec that changes architecture" + gdb_test "continue" "Breakpoint 2, main.*" "continue across exec that changes architecture" } -foreach follow_exec_mode {"same" "new"} { - do_test $follow_exec_mode +# Test handling the exec event with either the main thread or the +# second thread selected. This tries to ensure that GDB doesn't read +# registers off of the execing thread before figuring out its +# architecture. +foreach_with_prefix selected_thread {1 2} { + foreach_with_prefix follow_exec_mode {"same" "new"} { + do_test $follow_exec_mode $selected_thread + } } -- 2.30.2