[RFC PATCH 09/20] x86/virt/seamldr: Allocate and populate a module update request

[Chao Gao <chao.gao@intel.com>]

Allocate and populate a module update request, i.e., struct seamldr_params,
as defined in "SEAM Loader (SEAMLDR) Interface Specification" [1],
Revision 343755-004, Section 3.2.

struct seamldr_params includes a module binary, a sigstruct file, and an
update scenario. Parse the bitstream format, as defined by Intel, to
extract the binary and the sigstruct.

Currently, only the "UPDATE" scenario is supported.

Signed-off-by: Chao Gao <chao.gao@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
Link: https://cdrdv2.intel.com/v1/dl/getContent/733584 [1]
---
 arch/x86/virt/vmx/tdx/seamldr.c | 145 +++++++++++++++++++++++++++++++-
 1 file changed, 144 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index da862e71ebce..cdf85dff6d69 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -11,6 +11,8 @@
 #include <linux/firmware.h>
 #include <linux/gfp.h>
 #include <linux/kobject.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
 #include <linux/sysfs.h>
 
 #include "tdx.h"
@@ -41,6 +43,26 @@ struct tdx_status {
 	DECLARE_BITMAP(fw_state, TDX_FW_STATE_BITS);
 };
 
+/* SEAMLDR can accept up to 496 4KB pages for TDX module binary */
+#define SEAMLDR_MAX_NR_MODULE_4KB_PAGES	496
+
+/* scenario field in struct seamldr_params */
+#define SEAMLDR_SCENARIO_UPDATE		1
+
+/*
+ * Passed to P-SEAMLDR to describe information about the TDX module to install.
+ * Defined in "SEAM Loader (SEAMLDR) Interface Specification", Revision
+ * 343755-003, Section 3.2.
+ */
+struct seamldr_params {
+	u32	version;
+	u32	scenario;
+	u64	sigstruct_pa;
+	u8	reserved[104];
+	u64	num_module_pages;
+	u64	mod_pages_pa_list[SEAMLDR_MAX_NR_MODULE_4KB_PAGES];
+} __packed;
+
 struct fw_upload *tdx_fwl;
 static struct tdx_status tdx_status;
 static struct seamldr_info seamldr_info __aligned(256);
@@ -113,9 +135,130 @@ int get_seamldr_info(void)
 	return seamldr_call(P_SEAMLDR_INFO, &args);
 }
 
+static void free_seamldr_params(struct seamldr_params *params)
+{
+	free_page((unsigned long)params);
+}
+
+/* Allocate and populate a seamldr_params */
+static struct seamldr_params *alloc_seamldr_params(const void *module, int module_size,
+						   const void *sig, int sig_size)
+{
+	struct seamldr_params *params;
+	const u8 *ptr;
+	int i;
+
+	BUILD_BUG_ON(sizeof(struct seamldr_params) != SZ_4K);
+	if (module_size > SEAMLDR_MAX_NR_MODULE_4KB_PAGES * SZ_4K)
+		return ERR_PTR(-EINVAL);
+
+	/* current seamldr_params accepts one 4KB-page for sigstruct */
+	if (sig_size != SZ_4K)
+		return ERR_PTR(-EINVAL);
+
+	params = (struct seamldr_params *)get_zeroed_page(GFP_KERNEL);
+	if (!params)
+		return ERR_PTR(-ENOMEM);
+
+	params->scenario = SEAMLDR_SCENARIO_UPDATE;
+	params->sigstruct_pa = (vmalloc_to_pfn(sig) << PAGE_SHIFT) +
+			       ((unsigned long)sig & ~PAGE_MASK);
+	params->num_module_pages = DIV_ROUND_UP(module_size, SZ_4K);
+
+	ptr = module;
+	for (i = 0; i < params->num_module_pages; i++) {
+		params->mod_pages_pa_list[i] = (vmalloc_to_pfn(ptr) << PAGE_SHIFT) +
+					       ((unsigned long)ptr & ~PAGE_MASK);
+		ptr += SZ_4K;
+	}
+
+	return params;
+}
+
+struct tdx_blob {
+	u16	version;
+	u16	checksum;
+	u32	offset_of_module;
+	u8	signature[8];
+	u32	len;
+	u32	resv1;
+	u64	resv2[509];
+	u8	data[];
+} __packed;
+
+/* Verify that the checksum of the entire blob is zero */
+static bool verify_checksum(const struct tdx_blob *blob)
+{
+	u32 size = blob->len;
+	u16 checksum = 0;
+	const u16 *p;
+	int i;
+
+	/* Handle the last byte if the size is odd */
+	if (size % 2) {
+		checksum += *((const u8 *)blob + size - 1);
+		size--;
+	}
+
+	p = (const u16 *)blob;
+	for (i = 0; i < size; i += 2) {
+		checksum += *p;
+		p++;
+	}
+
+	return !checksum;
+}
+
+static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
+{
+	const struct tdx_blob *blob = (const void *)data;
+	const void *sig, *module;
+	int module_size, sig_size;
+
+	/* Split the given blob into a sigstruct and a module */
+	sig = blob->data;
+	sig_size = blob->offset_of_module - sizeof(struct tdx_blob);
+	module = data + blob->offset_of_module;
+	module_size = size - blob->offset_of_module;
+
+	if (sig_size <= 0 || module_size <= 0 || blob->len != size)
+		return ERR_PTR(-EINVAL);
+
+	if (memcmp(blob->signature, "TDX-BLOB", 8)) {
+		pr_err("invalid signature\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!verify_checksum(blob)) {
+		pr_err("invalid checksum\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	return alloc_seamldr_params(module, module_size, sig, sig_size);
+}
+
+/*
+ * Temporary flag to guard TD-Preserving updates. This will be removed once
+ * all necessary components for its support are integrated.
+ */
+static bool td_preserving_ready;
+
+DEFINE_FREE(free_seamldr_params, struct seamldr_params *,
+	    if (!IS_ERR_OR_NULL(_T)) free_seamldr_params(_T))
+
 static int seamldr_install_module(const u8 *data, u32 size)
 {
-	return -EOPNOTSUPP;
+	if (!td_preserving_ready)
+		return -EOPNOTSUPP;
+
+	struct seamldr_params *params __free(free_seamldr_params) =
+						init_seamldr_params(data, size);
+	if (IS_ERR(params))
+		return PTR_ERR(params);
+
+	/* TODO: Install and initialize the new TDX module */
+
+	return 0;
 }
 
 static enum fw_upload_err tdx_fw_prepare(struct fw_upload *fwl,
-- 
2.47.1