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, 74 insertions, 0 deletions

diff --git a/Documentation/userspace-api/dma-buf-heaps.rst b/Documentation/userspace-api/dma-buf-heaps.rst
new file mode 100644
index 000000000..f56b743cd
--- /dev/null
+++ b/Documentation/userspace-api/dma-buf-heaps.rst
@@ -0,0 +1,74 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================
+Allocating dma-buf using heaps
+==============================
+
+Dma-buf Heaps are a way for userspace to allocate dma-buf objects. They are
+typically used to allocate buffers from a specific allocation pool, or to share
+buffers across frameworks.
+
+Heaps
+=====
+
+A heap represents a specific allocator. The Linux kernel currently supports the
+following heaps:
+
+ - The ``system`` heap allocates virtually contiguous, cacheable, buffers.
+
+ - The ``system_cc_shared`` heap allocates virtually contiguous, cacheable,
+   buffers using shared (decrypted) memory. It is only present on
+   confidential computing (CoCo) VMs where memory encryption is active
+   (e.g., AMD SEV, Intel TDX). The allocated pages have the encryption
+   bit cleared, making them accessible for device DMA without TDISP
+   support. On non-CoCo VM configurations, this heap is not registered.
+
+ - The ``default_cma_region`` heap allocates physically contiguous,
+   cacheable, buffers. Only present if a CMA region is present. Such a
+   region is usually created either through the kernel commandline
+   through the ``cma`` parameter, a memory region Device-Tree node with
+   the ``linux,cma-default`` property set, or through the
+   ``CMA_SIZE_MBYTES`` or ``CMA_SIZE_PERCENTAGE`` Kconfig options. Prior
+   to Linux 6.17, its name wasn't stable and could be called
+   ``reserved``, ``linux,cma``, or ``default-pool``, depending on the
+   platform.
+
+ - A heap will be created for each reusable region in the device tree
+   with the ``shared-dma-pool`` compatible, using the full device tree
+   node name as its name. The buffer semantics are identical to
+   ``default-cma-region``.
+
+Naming Convention
+=================
+
+``dma-buf`` heaps name should meet a number of constraints:
+
+- The name must be stable, and must not change from one version to the other.
+  Userspace identifies heaps by their name, so if the names ever change, we
+  would be likely to introduce regressions.
+
+- The name must describe the memory region the heap will allocate from, and
+  must uniquely identify it in a given platform. Since userspace applications
+  use the heap name as the discriminant, it must be able to tell which heap it
+  wants to use reliably if there's multiple heaps.
+
+- The name must not mention implementation details, such as the allocator. The
+  heap driver will change over time, and implementation details when it was
+  introduced might not be relevant in the future.
+
+- The name should describe properties of the buffers that would be allocated.
+  Doing so will make heap identification easier for userspace. Such properties
+  are:
+
+  - ``contiguous`` for physically contiguous buffers;
+
+  - ``protected`` for encrypted buffers not accessible the OS;
+
+- The name may describe intended usage. Doing so will make heap identification
+  easier for userspace applications and users.
+
+For example, assuming a platform with a reserved memory region located
+at the RAM address 0x42000000, intended to allocate video framebuffers,
+physically contiguous, and backed by the CMA kernel allocator, good
+names would be ``memory@42000000-contiguous`` or ``video@42000000``, but
+``cma-video`` wouldn't.