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Peter Anvin" References: <20260513151045.1420990-1-chao.gao@intel.com> <20260513151045.1420990-12-chao.gao@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: <20260513151045.1420990-12-chao.gao@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/13/26 08:09, Chao Gao wrote: > 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. This is doing it again. It's taking the key imperative and burying it. It should be: => 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. <= > 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 flow. > > Signed-off-by: Chao Gao > --- > 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. That's a good note. It can go above the ---. > + * 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 called the "SEAMLDR_PARAMS" data structure and is defined > + * in "SEAM Loader (SEAMLDR) Interface Specification". > + * > + * It describes the TDX module that will be installed. Yeah, but that's not super useful. This 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. Better? > + */ > +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 > @@ -43,6 +71,89 @@ int seamldr_get_info(struct seamldr_info *seamldr_info) > } > EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host"); > > +#define TDX_IMAGE_VERSION_2 0x200 > + > +struct tdx_image_header { > + u16 version; // This ABI is always 0x200 That comment reads strangely in here. Did I ask you to write that? > + u16 checksum; > + u8 signature[8]; > + u32 sigstruct_nr_pages; > + u32 module_nr_pages; > + u8 reserved[4076]; > +} __packed; > + > +#define HEADER_SIZE sizeof(struct tdx_image_header) > +static_assert(HEADER_SIZE == 4096); > + > +/* Intel TDX module update ABI structure. aka. "TDX module blob". */ > +struct tdx_image { > + struct tdx_image_header header; > + u8 payload[]; // Contains sigstruct pages followed by module pages > +}; > + > +static void populate_pa_list(u64 *pa_list, u32 max_entries, const u8 *start, u32 nr_pages) The naming in there is painful. How about: populate_pa_list(u64 *pa_list, u32 pa_list_len, const u8 *vmalloc_addr, u32 vmalloc_len_pages) > +{ > + int i; > + > + nr_pages = MIN(nr_pages, max_entries); This seems wonky. Should it really be silently suppressing things if either the allocation or source is too small? I get not wanting to overflow, but this seems strange. > + for (i = 0; i < nr_pages; i++) { > + pa_list[i] = vmalloc_to_pfn(start) << PAGE_SHIFT; > + start += PAGE_SIZE; > + } At the point that you modify 'start', it's not 'start' any more. Use another variable. This would do, for instance: for (i = 0; i < nr_pages; i++) { unsigned long offset = i * PAGE_SIZE; pa_list[i] = vmalloc_to_pfn(&start[offset]); } > +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, SEAMLDR_MAX_NR_SIG_PAGES, > + sig, sig_nr_pages); > + populate_pa_list(params->module_pages_pa_list, SEAMLDR_MAX_NR_MODULE_PAGES, > + mod, mod_nr_pages); > +} Yes, this is starting to look OK. Nit: vertically align the "*_PAGES" args: populate_pa_list(params->sigstruct_pages_pa_list, SEAMLDR_..., sig, sig_nr_pages); populate_pa_list(params->module_pages_pa_list, SEAMLDR_..., mod, mod_nr_pages); > +static int init_seamldr_params(struct seamldr_params *params, const u8 *data, u32 size) > +{ > + const struct tdx_image *image = (const void *)data; > + 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 + 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 data size. */ > + if (HEADER_SIZE + sigstruct_len + module_len != size) > + return -EINVAL; > + > + /* > + * Don't care about user passing the wrong file, but protect > + * kernel ABI by preventing accepting garbage. > + */ How does this "protect kernel ABI"? > + if (header->version != TDX_IMAGE_VERSION_2) > + 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); Please work on the vertical alignment if there's a pattern. For instance, it makes things pop if the two "header->"'s are vertically aligned.