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authorSimon Marchi <simon.marchi@polymtl.ca>2021-02-22 11:41:32 -0500
committerSimon Marchi <simon.marchi@polymtl.ca>2021-02-22 11:41:32 -0500
commitde146e1946ee45f2552c6b56714793a2eba9b823 (patch)
tree1811fc36f8bbb5e772aefdbab83816e3eb755c28 /gdb/target.h
parente9d18e0649ae83fcfafd325a2366973efde43b38 (diff)
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gdb: push target earlier in procfs_target::attach (PR 27435)
Since this is a GDB 9 -> 10 regression, I would like to push it to gdb-10-branch. This is a follow-up to: https://sourceware.org/pipermail/gdb-patches/2021-February/176202.html This patch fixes a segfault seen when attaching to a process on Solaris. The steps leading to the segfault are: - procfs_target::attach calls do_attach, at this point the inferior's process slot in the target stack is empty. - do_attach adds a thread with `add_thread (&the_procfs_target, ptid)` - in add_thread_silent, the passed target (&the_procfs_target) is passed to find_inferior_ptid - find_inferior_ptid returns nullptr, as there is no inferior with this ptid that has &the_procfs_target as its process target - the nullptr `inf` is passed to find_thread_ptid, which dereferences it, causing a segfault - back in procfs_target::attach, after do_attach, we push the the_procfs_target on the inferior's target stack, although we never reach this because the segfault happens before. To fix this, I think we need to do the same as is done in inf_ptrace_target::attach: push the target early and unpush it in case the attach fails (and keep it if the attach succeeds). Implement it by moving target_unpush_up to target.h, so it can be re-used here. Make procfs_target::attach use it. Note that just like is mentioned in inf_ptrace_target::attach, we should push the target before calling target_pid_to_str, so that calling target_pid_to_str ends up in procfs_target::pid_to_str. Tested by trying to attach on a process on gcc211 on the gcc compile farm. gdb/ChangeLog: PR gdb/27435 * inf-ptrace.c (struct target_unpusher): Move to target.h. (target_unpush_up): Likewise. * procfs.c (procfs_target::attach): Push target early. Use target_unpush_up to unpush target in case of error. * target.h (struct target_unpusher): Move here. (target_unpush_up): Likewise. Change-Id: I88aff8b20204e1ca1d792e27ac6bc34fc1aa0d52
Diffstat (limited to 'gdb/target.h')
-rw-r--r--gdb/target.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/gdb/target.h b/gdb/target.h
index 0de7807..52e23b0 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -2392,6 +2392,20 @@ extern void push_target (target_ops_up &&);
extern int unpush_target (struct target_ops *);
+/* A unique_ptr helper to unpush a target. */
+
+struct target_unpusher
+{
+ void operator() (struct target_ops *ops) const
+ {
+ unpush_target (ops);
+ }
+};
+
+/* A unique_ptr that unpushes a target on destruction. */
+
+typedef std::unique_ptr<struct target_ops, target_unpusher> target_unpush_up;
+
extern void target_pre_inferior (int);
extern void target_preopen (int);