objtool: Validate disassembler headers in libopcodes probegrafted

commit 3f2de814c059 ("objtool: Fix libopcodes linking with static libraries")
tested for libopcodes availability by linking a test snippet with a forward
declaration of disassemble_init_for_target().

However, testing symbol linkage with an extern declaration only verifies
the presence of the library (.so/.a) and bypasses checking for development
headers (binutils-dev). On systems where libopcodes is present without
development headers installed, the probe succeeds, enabling BUILD_DISAS.
Subsequent compilation of objtool then fails:

  fatal error: 'bfd.h' file not found
    113 | #include <bfd.h>

Additionally, the probe invokes $(HOSTCC) without $(HOSTCFLAGS), ignoring
any sysroot or include flags specified for the host compiler.

Fix this by including <bfd.h> and <dis-asm.h> directly in the test snippet,
passing $(HOSTCFLAGS) so host compiler options are respected, and defining
PACKAGE="objtool" to satisfy the configuration check in <bfd.h>.

Fixes: 3f2de814c059 ("objtool: Fix libopcodes linking with static libraries")
Fixes: 436326bc525d ("objtool: fix build failure due to missing libopcodes check")
Reported-by: Alice Ryhl <aliceryhl@google.com>
Assisted-by: Antigravity:Gemini-Next
Signed-off-by: Ulises Mendez Martinez <umendez@google.com>
Link: https://patch.msgid.link/20260904150710.2997558-1-umendez@google.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/Documentation/filesystems/devpts.rst b/Documentation/filesystems/devpts.rst
new file mode 100644
index 000000000..b6324ab19
--- /dev/null
+++ b/Documentation/filesystems/devpts.rst
@@ -0,0 +1,36 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================
+The Devpts Filesystem
+=====================
+
+Each mount of the devpts filesystem is now distinct such that ptys
+and their indices allocated in one mount are independent from ptys
+and their indices in all other mounts.
+
+All mounts of the devpts filesystem now create a ``/dev/pts/ptmx`` node
+with permissions ``0000``.
+
+To retain backwards compatibility the a ptmx device node (aka any node
+created with ``mknod name c 5 2``) when opened will look for an instance
+of devpts under the name ``pts`` in the same directory as the ptmx device
+node.
+
+As an option instead of placing a ``/dev/ptmx`` device node at ``/dev/ptmx``
+it is possible to place a symlink to ``/dev/pts/ptmx`` at ``/dev/ptmx`` or
+to bind mount ``/dev/ptx/ptmx`` to ``/dev/ptmx``.  If you opt for using
+the devpts filesystem in this manner devpts should be mounted with
+the ``ptmxmode=0666``, or ``chmod 0666 /dev/pts/ptmx`` should be called.
+
+Total count of pty pairs in all instances is limited by sysctls::
+
+    kernel.pty.max = 4096	- global limit
+    kernel.pty.reserve = 1024	- reserved for filesystems mounted from the initial mount namespace
+    kernel.pty.nr		- current count of ptys
+
+Per-instance limit could be set by adding mount option ``max=<count>``.
+
+This feature was added in kernel 3.4 together with
+``sysctl kernel.pty.reserve``.
+
+In kernels older than 3.4 sysctl ``kernel.pty.max`` works as per-instance limit.