[PATCH] Fallback to direct access if lacking pemission for linux namespaces

[Tyson Whitehead <twhitehead@gmail.com>]

The case where gdb and the target had the same path always used to
work. Now it fails if gdb and the target are in different namespaces
and gdb doesn't have permission to enter the target namespace.

This commit causes gdb to fall back to trying direct access should
it lack permission to enter the namespace. This way it does not
break a case that used to work or require capabilites not required.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30113
---
 gdb/nat/linux-namespaces.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gdb/nat/linux-namespaces.c b/gdb/nat/linux-namespaces.c
index 4b1fee18425..8922717be10 100644
--- a/gdb/nat/linux-namespaces.c
+++ b/gdb/nat/linux-namespaces.c
@@ -935,6 +935,13 @@ linux_mntns_access_fs (pid_t pid)
 	  if (error == ENOSYS)
 	    error = ENOTSUP;
 
+	  /* EPERM indicates the required capabilites are not available
+	     for this. Fall back to the old direct gdb behaviour in
+	     order to not break cases where this used to work as the
+	     path could still be the same in both namespaces. */
+	  if (error == EPERM)
+	    return MNSH_FS_DIRECT;
+
 	  errno = error;
 	  return MNSH_FS_ERROR;
 	}
-- 
2.40.1