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, 48 insertions, 0 deletions

diff --git a/lib/test_free_pages.c b/lib/test_free_pages.c
new file mode 100644
index 000000000..48952364c
--- /dev/null
+++ b/lib/test_free_pages.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * test_free_pages.c: Check that free_pages() doesn't leak memory
+ * Copyright (c) 2020 Oracle
+ * Author: Matthew Wilcox <willy@infradead.org>
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+
+static void test_free_pages(gfp_t gfp)
+{
+	unsigned int i;
+
+	for (i = 0; i < 1000 * 1000; i++) {
+		unsigned long addr = __get_free_pages(gfp, 3);
+		struct page *page = virt_to_page((void *)addr);
+
+		/* Simulate page cache getting a speculative reference */
+		get_page(page);
+		free_pages(addr, 3);
+		put_page(page);
+	}
+}
+
+static int m_in(void)
+{
+	pr_info("Testing with GFP_KERNEL\n");
+	test_free_pages(GFP_KERNEL);
+	pr_info("Testing with GFP_KERNEL | __GFP_COMP\n");
+	test_free_pages(GFP_KERNEL | __GFP_COMP);
+	pr_info("Test completed\n");
+
+	return 0;
+}
+
+static void m_ex(void)
+{
+}
+
+module_init(m_in);
+module_exit(m_ex);
+MODULE_AUTHOR("Matthew Wilcox <willy@infradead.org>");
+MODULE_DESCRIPTION("Check that free_pages() doesn't leak memory");
+MODULE_LICENSE("GPL");