x86/virt/seamldr: Allocate and populate a module update request

There are two important ABIs here:

'struct tdx_image'	- The on-disk and in-memory format for a TDX
			  module update image.
'struct seamldr_params'	- The in-memory ABI passed to the TDX module
			  loader. Points to a single 'struct tdx_image'
			  broken up into 4k pages.

Userspace supplies the update image in 'struct tdx_image' format. The
image consists of a header followed by a sigstruct and the module
binary. P-SEAMLDR, however, consumes 'struct seamldr_params' rather
than the image directly.

Parse the 'struct tdx_image' provided by userspace and populate a
matching 'struct seamldr_params'.

The 'tdx_image' ABI is versioned. Two public versions exist today:
0x100 and 0x200. This kernel only accepts 0x200. The older 0x100
format is being deprecated and is intentionally not supported here.
Future versions of the module might be able to use the same ABIs
(user/kernel and kernel/SEAMLDR) but they will not be able to use this
kernel code.

Reject module images without that specific version. This ensures that
the kernel is able to understand the passed-in format.

Validate the 'struct tdx_image' header before using it, because the
header is consumed solely by the kernel to locate the sigstruct and
module within the image. Do not validate the payload itself. The
sigstruct and module pages are passed through to P-SEAMLDR, which
validates them as part of the update.

sigstruct_pages_pa_list currently has only one entry, but it will grow
to four pages in the future. Keep it as an array for symmetry with
module_pages_pa_list and for extensibility.

[ dhansen: normal changelog clarification/munging ]

Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260520133909.409394-14-chao.gao@intel.com

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index b2b6a439d41770110d215a7c9f9c007cb173f603..bcb1386380ef5c4a5f103de128a14a2fe49ece80 100644 (file)
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -7,6 +7,8 @@
 #define pr_fmt(fmt)    "seamldr: " fmt
 
 #include <linux/bug.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
 #include <linux/spinlock.h>
 
 #include <asm/cpufeature.h>
@@ -18,6 +20,35 @@
 /* P-SEAMLDR SEAMCALL leaf function */
 #define P_SEAMLDR_INFO                 0x8000000000000000
 
+#define SEAMLDR_MAX_NR_MODULE_PAGES    496
+#define SEAMLDR_MAX_NR_SIG_PAGES       1
+
+/*
+ * The seamldr_params "scenario" field specifies the operation mode:
+ * 0: Install TDX module from scratch (not used by kernel)
+ * 1: Update existing TDX module to a compatible version
+ */
+#define SEAMLDR_SCENARIO_UPDATE                1
+
+/*
+ * This is the "SEAMLDR_PARAMS" data structure defined in the
+ * "SEAM Loader (SEAMLDR) Interface Specification".
+ *
+ * It is the in-memory ABI that the kernel passes to the P-SEAMLDR
+ * to update the TDX module. It breaks the TDX module image up in
+ * page-size pieces.
+ */
+struct seamldr_params {
+       u32     version;
+       u32     scenario;
+       u64     sigstruct_pages_pa_list[SEAMLDR_MAX_NR_SIG_PAGES];
+       u8      reserved[104];
+       u64     module_nr_pages;
+       u64     module_pages_pa_list[SEAMLDR_MAX_NR_MODULE_PAGES];
+} __packed;
+
+static_assert(sizeof(struct seamldr_params) == 4096);
+
 /*
  * Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
  * interact with P-SEAMLDR simultaneously. Use raw version as the calls can
@@ -55,6 +86,106 @@ int seamldr_get_info(struct seamldr_info *seamldr_info)
 }
 EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
 
+#define TDX_IMAGE_VERSION_2            0x200
+
+/* First page of the on-disk module update image: */
+struct tdx_image_header {
+       u16     version;
+       u16     checksum;
+       u8      signature[8];
+       u32     sigstruct_nr_pages;
+       u32     module_nr_pages;
+       u8      reserved[4076];
+} __packed;
+
+#define TDX_IMAGE_HEADER_SIZE sizeof(struct tdx_image_header)
+static_assert(TDX_IMAGE_HEADER_SIZE == 4096);
+
+/*
+ * Intel TDX module update ABI structure. aka. "TDX module blob".
+ * This is the on-disk format that fw_upload lands in a kernel
+ * buffer.
+ *
+ * @payload contains sigstruct pages followed by module pages.
+ */
+struct tdx_image {
+       struct tdx_image_header header;
+       u8 payload[];
+};
+
+/*
+ * Given a vmalloc() allocation, write all of the backing physical
+ * addresses to pa_list[]. Caller guarantees that the array is big
+ * enough.
+ */
+static void populate_pa_list(u64 *pa_list, const u8 *vmalloc_addr, u32 vmalloc_len_pages)
+{
+       int i;
+
+       for (i = 0; i < vmalloc_len_pages; i++) {
+               unsigned long offset = i * PAGE_SIZE;
+               unsigned long pfn = vmalloc_to_pfn(&vmalloc_addr[offset]);
+
+               pa_list[i] = pfn << PAGE_SHIFT;
+       }
+}
+
+static void populate_seamldr_params(struct seamldr_params *params,
+                                   const u8 *sig, u32 sig_nr_pages,
+                                   const u8 *mod, u32 mod_nr_pages)
+{
+       params->version         = 0;
+       params->scenario        = SEAMLDR_SCENARIO_UPDATE;
+       params->module_nr_pages = mod_nr_pages;
+
+       populate_pa_list(params->sigstruct_pages_pa_list, sig, sig_nr_pages);
+       populate_pa_list(params->module_pages_pa_list,    mod, mod_nr_pages);
+}
+
+/*
+ * @image points to a vmalloc()'d 'struct tdx_image'. Transform
+ * it into @params which is the P-SEAMLDR ABI format.
+ */
+static int init_seamldr_params(struct seamldr_params *params,
+                              const struct tdx_image *image,
+                              u32 image_len)
+{
+       const struct tdx_image_header *header   = &image->header;
+
+       u32 sigstruct_len       = header->sigstruct_nr_pages * PAGE_SIZE;
+       u32 module_len          = header->module_nr_pages    * PAGE_SIZE;
+
+       u8 *header_start        = (u8 *)header;
+       u8 *header_end          = header_start + TDX_IMAGE_HEADER_SIZE;
+
+       u8 *sigstruct_start     = header_end;
+       u8 *sigstruct_end       = sigstruct_start + sigstruct_len;
+
+       u8 *module_start        = sigstruct_end;
+
+       /* Check the calculated payload size against the image size. */
+       if (TDX_IMAGE_HEADER_SIZE + sigstruct_len + module_len != image_len)
+               return -EINVAL;
+
+       /* Reject unsupported tdx_image ABI versions. */
+       if (header->version != TDX_IMAGE_VERSION_2)
+               return -EINVAL;
+
+       if (header->sigstruct_nr_pages > SEAMLDR_MAX_NR_SIG_PAGES ||
+           header->module_nr_pages    > SEAMLDR_MAX_NR_MODULE_PAGES)
+               return -EINVAL;
+
+       if (memcmp(header->signature, "TDX-BLOB", sizeof(header->signature)))
+               return -EINVAL;
+
+       if (memchr_inv(header->reserved, 0, sizeof(header->reserved)))
+               return -EINVAL;
+
+       populate_seamldr_params(params, sigstruct_start, header->sigstruct_nr_pages,
+                                       module_start,    header->module_nr_pages);
+       return 0;
+}
+
 /**
  * seamldr_install_module - Install a new TDX module.
  * @data: Pointer to the TDX module image.
@@ -64,7 +195,31 @@ EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
  */
 int seamldr_install_module(const u8 *data, u32 data_len)
 {
+       struct seamldr_params *params;
+       const struct tdx_image *image;
+       int ret;
+
+       /*
+        * init_seamldr_params() reads the header early.
+        * Ensure there is enough data to do at least that.
+        */
+       if (data_len < TDX_IMAGE_HEADER_SIZE)
+               return -EINVAL;
+
+       image = (const struct tdx_image *)data;
+
+       params = kzalloc_obj(*params);
+       if (!params)
+               return -ENOMEM;
+
+       /* Populate 'params' from 'image'. */
+       ret = init_seamldr_params(params, image, data_len);
+       if (ret)
+               goto out;
+
        /* TODO: Update TDX module here */
-       return 0;
+out:
+       kfree(params);
+       return ret;
 }
 EXPORT_SYMBOL_FOR_MODULES(seamldr_install_module, "tdx-host");