[PATCHv4 06/12] kexec: Integrate with the introduced bpf kfuncs

[Pingfan Liu <piliu@redhat.com>]

This patch does two things:
First, register as a listener on bpf_copy_to_kernel()
Second, in order that the hooked bpf-prog can call the sleepable kfuncs,
bpf_handle_pefile and bpf_post_handle_pefile are marked as
KF_SLEEPABLE.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Philipp Rudo <prudo@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: bpf@vger.kernel.org
To: kexec@lists.infradead.org
---
 kernel/kexec_pe_image.c | 67 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/kernel/kexec_pe_image.c b/kernel/kexec_pe_image.c
index b0cf9942e68d2..f8debcde6b516 100644
--- a/kernel/kexec_pe_image.c
+++ b/kernel/kexec_pe_image.c
@@ -38,6 +38,51 @@ static struct kexec_res parsed_resource[3] = {
 	{ KEXEC_RES_CMDLINE_NAME, },
 };
 
+/*
+ * @name should be one of : kernel, initrd, cmdline
+ */
+static int bpf_kexec_carrier(const char *name, struct mem_range_result *r)
+{
+	struct kexec_res *res;
+	int i;
+
+	if (!r || !name)
+		return -EINVAL;
+
+	for (i = 0; i < 3; i++) {
+		if (!strcmp(parsed_resource[i].name, name))
+			break;
+	}
+	if (i >= 3)
+		return -EINVAL;
+
+	res = &parsed_resource[i];
+	/*
+	 * Replace the intermediate resource generated by the previous step.
+	 */
+	if (!!res->r)
+		mem_range_result_put(res->r);
+	mem_range_result_get(r);
+	res->r = r;
+	return 0;
+}
+
+static struct carrier_listener kexec_res_listener[3] = {
+	{ .name = KEXEC_RES_KERNEL_NAME,
+	  .alloc_type = 1,
+	  .handler = bpf_kexec_carrier,
+	},
+	{ .name = KEXEC_RES_INITRD_NAME,
+	  .alloc_type = 1,
+	  .handler = bpf_kexec_carrier,
+	},
+	{ .name = KEXEC_RES_CMDLINE_NAME,
+	  /* kmalloc-ed */
+	  .alloc_type = 0,
+	  .handler = bpf_kexec_carrier,
+	},
+};
+
 static bool pe_has_bpf_section(const char *file_buf, unsigned long pe_sz);
 
 static bool is_valid_pe(const char *kernel_buf, unsigned long kernel_len)
@@ -159,6 +204,22 @@ __attribute__((used, optimize("O0"))) void bpf_post_handle_pefile(struct kexec_c
 	dummy += 2;
 }
 
+BTF_KFUNCS_START(kexec_modify_return_ids)
+BTF_ID_FLAGS(func, bpf_handle_pefile, KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_post_handle_pefile, KF_SLEEPABLE)
+BTF_KFUNCS_END(kexec_modify_return_ids)
+
+static const struct btf_kfunc_id_set kexec_modify_return_set = {
+	.owner = THIS_MODULE,
+	.set = &kexec_modify_return_ids,
+};
+
+static int __init kexec_bpf_prog_run_init(void)
+{
+	return register_btf_fmodret_id_set(&kexec_modify_return_set);
+}
+late_initcall(kexec_bpf_prog_run_init);
+
 /*
  * PE file may be nested and should be unfold one by one.
  * Query 'kernel', 'initrd', 'cmdline' in cur_phase, as they are inputs for the
@@ -213,6 +274,9 @@ static void *pe_image_load(struct kimage *image,
 	cmdline_start = cmdline;
 	cmdline_sz = cmdline_len;
 
+	for (int i = 0; i < ARRAY_SIZE(kexec_res_listener); i++)
+		register_carrier_listener(&kexec_res_listener[i]);
+
 	while (is_valid_format(linux_start, linux_sz) &&
 	       pe_has_bpf_section(linux_start, linux_sz)) {
 		struct kexec_context context;
@@ -250,6 +314,9 @@ static void *pe_image_load(struct kimage *image,
 		disarm_bpf_prog();
 	}
 
+	for (int i = 0; i < ARRAY_SIZE(kexec_res_listener); i++)
+		unregister_carrier_listener(kexec_res_listener[i].name);
+
 	/*
 	 * image's kernel_buf, initrd_buf, cmdline_buf are set. Now they should
 	 * be updated to the new content.
-- 
2.49.0