kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 306 insertions, 0 deletions

diff --git a/net/bluetooth/selftest.c b/net/bluetooth/selftest.c
new file mode 100644
index 000000000..ae5b44bb9
--- /dev/null
+++ b/net/bluetooth/selftest.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+   BlueZ - Bluetooth protocol stack for Linux
+
+   Copyright (C) 2014 Intel Corporation
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
+   IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
+   CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
+   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+   ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
+   COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
+   SOFTWARE IS DISCLAIMED.
+*/
+
+#include <linux/debugfs.h>
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+
+#include "ecdh_helper.h"
+#include "smp.h"
+#include "selftest.h"
+
+#if IS_ENABLED(CONFIG_BT_SELFTEST_ECDH)
+
+static const u8 priv_a_1[32] __initconst = {
+	0xbd, 0x1a, 0x3c, 0xcd, 0xa6, 0xb8, 0x99, 0x58,
+	0x99, 0xb7, 0x40, 0xeb, 0x7b, 0x60, 0xff, 0x4a,
+	0x50, 0x3f, 0x10, 0xd2, 0xe3, 0xb3, 0xc9, 0x74,
+	0x38, 0x5f, 0xc5, 0xa3, 0xd4, 0xf6, 0x49, 0x3f,
+};
+static const u8 priv_b_1[32] __initconst = {
+	0xfd, 0xc5, 0x7f, 0xf4, 0x49, 0xdd, 0x4f, 0x6b,
+	0xfb, 0x7c, 0x9d, 0xf1, 0xc2, 0x9a, 0xcb, 0x59,
+	0x2a, 0xe7, 0xd4, 0xee, 0xfb, 0xfc, 0x0a, 0x90,
+	0x9a, 0xbb, 0xf6, 0x32, 0x3d, 0x8b, 0x18, 0x55,
+};
+static const u8 pub_a_1[64] __initconst = {
+	0xe6, 0x9d, 0x35, 0x0e, 0x48, 0x01, 0x03, 0xcc,
+	0xdb, 0xfd, 0xf4, 0xac, 0x11, 0x91, 0xf4, 0xef,
+	0xb9, 0xa5, 0xf9, 0xe9, 0xa7, 0x83, 0x2c, 0x5e,
+	0x2c, 0xbe, 0x97, 0xf2, 0xd2, 0x03, 0xb0, 0x20,
+
+	0x8b, 0xd2, 0x89, 0x15, 0xd0, 0x8e, 0x1c, 0x74,
+	0x24, 0x30, 0xed, 0x8f, 0xc2, 0x45, 0x63, 0x76,
+	0x5c, 0x15, 0x52, 0x5a, 0xbf, 0x9a, 0x32, 0x63,
+	0x6d, 0xeb, 0x2a, 0x65, 0x49, 0x9c, 0x80, 0xdc,
+};
+static const u8 pub_b_1[64] __initconst = {
+	0x90, 0xa1, 0xaa, 0x2f, 0xb2, 0x77, 0x90, 0x55,
+	0x9f, 0xa6, 0x15, 0x86, 0xfd, 0x8a, 0xb5, 0x47,
+	0x00, 0x4c, 0x9e, 0xf1, 0x84, 0x22, 0x59, 0x09,
+	0x96, 0x1d, 0xaf, 0x1f, 0xf0, 0xf0, 0xa1, 0x1e,
+
+	0x4a, 0x21, 0xb1, 0x15, 0xf9, 0xaf, 0x89, 0x5f,
+	0x76, 0x36, 0x8e, 0xe2, 0x30, 0x11, 0x2d, 0x47,
+	0x60, 0x51, 0xb8, 0x9a, 0x3a, 0x70, 0x56, 0x73,
+	0x37, 0xad, 0x9d, 0x42, 0x3e, 0xf3, 0x55, 0x4c,
+};
+static const u8 dhkey_1[32] __initconst = {
+	0x98, 0xa6, 0xbf, 0x73, 0xf3, 0x34, 0x8d, 0x86,
+	0xf1, 0x66, 0xf8, 0xb4, 0x13, 0x6b, 0x79, 0x99,
+	0x9b, 0x7d, 0x39, 0x0a, 0xa6, 0x10, 0x10, 0x34,
+	0x05, 0xad, 0xc8, 0x57, 0xa3, 0x34, 0x02, 0xec,
+};
+
+static const u8 priv_a_2[32] __initconst = {
+	0x63, 0x76, 0x45, 0xd0, 0xf7, 0x73, 0xac, 0xb7,
+	0xff, 0xdd, 0x03, 0x72, 0xb9, 0x72, 0x85, 0xb4,
+	0x41, 0xb6, 0x5d, 0x0c, 0x5d, 0x54, 0x84, 0x60,
+	0x1a, 0xa3, 0x9a, 0x3c, 0x69, 0x16, 0xa5, 0x06,
+};
+static const u8 priv_b_2[32] __initconst = {
+	0xba, 0x30, 0x55, 0x50, 0x19, 0xa2, 0xca, 0xa3,
+	0xa5, 0x29, 0x08, 0xc6, 0xb5, 0x03, 0x88, 0x7e,
+	0x03, 0x2b, 0x50, 0x73, 0xd4, 0x2e, 0x50, 0x97,
+	0x64, 0xcd, 0x72, 0x0d, 0x67, 0xa0, 0x9a, 0x52,
+};
+static const u8 pub_a_2[64] __initconst = {
+	0xdd, 0x78, 0x5c, 0x74, 0x03, 0x9b, 0x7e, 0x98,
+	0xcb, 0x94, 0x87, 0x4a, 0xad, 0xfa, 0xf8, 0xd5,
+	0x43, 0x3e, 0x5c, 0xaf, 0xea, 0xb5, 0x4c, 0xf4,
+	0x9e, 0x80, 0x79, 0x57, 0x7b, 0xa4, 0x31, 0x2c,
+
+	0x4f, 0x5d, 0x71, 0x43, 0x77, 0x43, 0xf8, 0xea,
+	0xd4, 0x3e, 0xbd, 0x17, 0x91, 0x10, 0x21, 0xd0,
+	0x1f, 0x87, 0x43, 0x8e, 0x40, 0xe2, 0x52, 0xcd,
+	0xbe, 0xdf, 0x98, 0x38, 0x18, 0x12, 0x95, 0x91,
+};
+static const u8 pub_b_2[64] __initconst = {
+	0xcc, 0x00, 0x65, 0xe1, 0xf5, 0x6c, 0x0d, 0xcf,
+	0xec, 0x96, 0x47, 0x20, 0x66, 0xc9, 0xdb, 0x84,
+	0x81, 0x75, 0xa8, 0x4d, 0xc0, 0xdf, 0xc7, 0x9d,
+	0x1b, 0x3f, 0x3d, 0xf2, 0x3f, 0xe4, 0x65, 0xf4,
+
+	0x79, 0xb2, 0xec, 0xd8, 0xca, 0x55, 0xa1, 0xa8,
+	0x43, 0x4d, 0x6b, 0xca, 0x10, 0xb0, 0xc2, 0x01,
+	0xc2, 0x33, 0x4e, 0x16, 0x24, 0xc4, 0xef, 0xee,
+	0x99, 0xd8, 0xbb, 0xbc, 0x48, 0xd0, 0x01, 0x02,
+};
+static const u8 dhkey_2[32] __initconst = {
+	0x69, 0xeb, 0x21, 0x32, 0xf2, 0xc6, 0x05, 0x41,
+	0x60, 0x19, 0xcd, 0x5e, 0x94, 0xe1, 0xe6, 0x5f,
+	0x33, 0x07, 0xe3, 0x38, 0x4b, 0x68, 0xe5, 0x62,
+	0x3f, 0x88, 0x6d, 0x2f, 0x3a, 0x84, 0x85, 0xab,
+};
+
+static const u8 priv_a_3[32] __initconst = {
+	0xbd, 0x1a, 0x3c, 0xcd, 0xa6, 0xb8, 0x99, 0x58,
+	0x99, 0xb7, 0x40, 0xeb, 0x7b, 0x60, 0xff, 0x4a,
+	0x50, 0x3f, 0x10, 0xd2, 0xe3, 0xb3, 0xc9, 0x74,
+	0x38, 0x5f, 0xc5, 0xa3, 0xd4, 0xf6, 0x49, 0x3f,
+};
+static const u8 pub_a_3[64] __initconst = {
+	0xe6, 0x9d, 0x35, 0x0e, 0x48, 0x01, 0x03, 0xcc,
+	0xdb, 0xfd, 0xf4, 0xac, 0x11, 0x91, 0xf4, 0xef,
+	0xb9, 0xa5, 0xf9, 0xe9, 0xa7, 0x83, 0x2c, 0x5e,
+	0x2c, 0xbe, 0x97, 0xf2, 0xd2, 0x03, 0xb0, 0x20,
+
+	0x8b, 0xd2, 0x89, 0x15, 0xd0, 0x8e, 0x1c, 0x74,
+	0x24, 0x30, 0xed, 0x8f, 0xc2, 0x45, 0x63, 0x76,
+	0x5c, 0x15, 0x52, 0x5a, 0xbf, 0x9a, 0x32, 0x63,
+	0x6d, 0xeb, 0x2a, 0x65, 0x49, 0x9c, 0x80, 0xdc,
+};
+static const u8 dhkey_3[32] __initconst = {
+	0x2d, 0xab, 0x00, 0x48, 0xcb, 0xb3, 0x7b, 0xda,
+	0x55, 0x7b, 0x8b, 0x72, 0xa8, 0x57, 0x87, 0xc3,
+	0x87, 0x27, 0x99, 0x32, 0xfc, 0x79, 0x5f, 0xae,
+	0x7c, 0x1c, 0xf9, 0x49, 0xe6, 0xd7, 0xaa, 0x70,
+};
+
+static int __init test_ecdh_sample(struct crypto_kpp *tfm, const u8 priv_a[32],
+				   const u8 priv_b[32], const u8 pub_a[64],
+				   const u8 pub_b[64], const u8 dhkey[32])
+{
+	u8 *tmp, *dhkey_a, *dhkey_b;
+	int ret;
+
+	tmp = kmalloc(64, GFP_KERNEL);
+	if (!tmp)
+		return -EINVAL;
+
+	dhkey_a = &tmp[0];
+	dhkey_b = &tmp[32];
+
+	ret = set_ecdh_privkey(tfm, priv_a);
+	if (ret)
+		goto out;
+
+	ret = compute_ecdh_secret(tfm, pub_b, dhkey_a);
+	if (ret)
+		goto out;
+
+	if (memcmp(dhkey_a, dhkey, 32)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = set_ecdh_privkey(tfm, priv_b);
+	if (ret)
+		goto out;
+
+	ret = compute_ecdh_secret(tfm, pub_a, dhkey_b);
+	if (ret)
+		goto out;
+
+	if (memcmp(dhkey_b, dhkey, 32))
+		ret = -EINVAL;
+	/* fall through*/
+out:
+	kfree(tmp);
+	return ret;
+}
+
+static char test_ecdh_buffer[32];
+
+static ssize_t test_ecdh_read(struct file *file, char __user *user_buf,
+			      size_t count, loff_t *ppos)
+{
+	return simple_read_from_buffer(user_buf, count, ppos, test_ecdh_buffer,
+				       strlen(test_ecdh_buffer));
+}
+
+static const struct file_operations test_ecdh_fops = {
+	.open		= simple_open,
+	.read		= test_ecdh_read,
+	.llseek		= default_llseek,
+};
+
+static int __init test_ecdh(void)
+{
+	struct crypto_kpp *tfm;
+	ktime_t calltime, delta, rettime;
+	unsigned long long duration = 0;
+	int err;
+
+	calltime = ktime_get();
+
+	tfm = crypto_alloc_kpp("ecdh-nist-p256", 0, 0);
+	if (IS_ERR(tfm)) {
+		BT_ERR("Unable to create ECDH crypto context");
+		err = PTR_ERR(tfm);
+		goto done;
+	}
+
+	err = test_ecdh_sample(tfm, priv_a_1, priv_b_1, pub_a_1, pub_b_1,
+			       dhkey_1);
+	if (err) {
+		BT_ERR("ECDH sample 1 failed");
+		goto done;
+	}
+
+	err = test_ecdh_sample(tfm, priv_a_2, priv_b_2, pub_a_2, pub_b_2,
+			       dhkey_2);
+	if (err) {
+		BT_ERR("ECDH sample 2 failed");
+		goto done;
+	}
+
+	err = test_ecdh_sample(tfm, priv_a_3, priv_a_3, pub_a_3, pub_a_3,
+			       dhkey_3);
+	if (err) {
+		BT_ERR("ECDH sample 3 failed");
+		goto done;
+	}
+
+	crypto_free_kpp(tfm);
+
+	rettime = ktime_get();
+	delta = ktime_sub(rettime, calltime);
+	duration = (unsigned long long) ktime_to_ns(delta) >> 10;
+
+	BT_INFO("ECDH test passed in %llu usecs", duration);
+
+done:
+	if (!err)
+		snprintf(test_ecdh_buffer, sizeof(test_ecdh_buffer),
+			 "PASS (%llu usecs)\n", duration);
+	else
+		snprintf(test_ecdh_buffer, sizeof(test_ecdh_buffer), "FAIL\n");
+
+	debugfs_create_file("selftest_ecdh", 0444, bt_debugfs, NULL,
+			    &test_ecdh_fops);
+
+	return err;
+}
+
+#else
+
+static inline int test_ecdh(void)
+{
+	return 0;
+}
+
+#endif
+
+static int __init run_selftest(void)
+{
+	int err;
+
+	BT_INFO("Starting self testing");
+
+	err = test_ecdh();
+	if (err)
+		goto done;
+
+	err = bt_selftest_smp();
+
+done:
+	BT_INFO("Finished self testing");
+
+	return err;
+}
+
+#if IS_MODULE(CONFIG_BT)
+
+/* This is run when CONFIG_BT_SELFTEST=y and CONFIG_BT=m and is just a
+ * wrapper to allow running this at module init.
+ *
+ * If CONFIG_BT_SELFTEST=n, then this code is not compiled at all.
+ */
+int __init bt_selftest(void)
+{
+	return run_selftest();
+}
+
+#else
+
+/* This is run when CONFIG_BT_SELFTEST=y and CONFIG_BT=y and is run
+ * via late_initcall() as last item in the initialization sequence.
+ *
+ * If CONFIG_BT_SELFTEST=n, then this code is not compiled at all.
+ */
+static int __init bt_selftest_init(void)
+{
+	return run_selftest();
+}
+late_initcall(bt_selftest_init);
+
+#endif