Re: [PATCH v41 20/24] selftests/x86: Add a selftest for SGX

On Fri, Nov 13, 2020 at 12:01:31AM +0200, Jarkko Sakkinen wrote:

+bool encl_load(const char *path, struct encl *encl) +{

• Elf64_Phdr *phdr_tbl;
• off_t src_offset;
• Elf64_Ehdr *ehdr;
• int i, j;
• int ret;
• memset(encl, 0, sizeof(*encl));
• ret = open("/dev/sgx_enclave", O_RDWR);
• if (ret < 0) {

• fprintf(stderr, "Unable to open /dev/sgx_enclave\n");
  

• goto err;
  

• }
• encl->fd = ret;
• if (!encl_map_bin(path, encl))

• goto err;
  

• ehdr = encl->bin;
• phdr_tbl = encl->bin + ehdr->e_phoff;
• for (i = 0; i < ehdr->e_phnum; i++) {

• Elf64_Phdr *phdr = &phdr_tbl[i];
  

• if (phdr->p_type == PT_LOAD)
  

• 	encl->nr_segments++;
  

• }
• encl->segment_tbl = calloc(encl->nr_segments,

• 		   sizeof(struct encl_segment));
  

• if (!encl->segment_tbl)

• goto err;
  

• for (i = 0, j = 0; i < ehdr->e_phnum; i++) {

• Elf64_Phdr *phdr = &phdr_tbl[i];
  

• unsigned int flags = phdr->p_flags;
  

• struct encl_segment *seg;
  

• if (phdr->p_type != PT_LOAD)
  

• 	continue;
  

• seg = &encl->segment_tbl[j];
  

• if (!!(flags & ~(PF_R | PF_W | PF_X))) {
  

• 	fprintf(stderr,
  

• 		"%d has invalid segment flags 0x%02x.\n", i,
  

• 		phdr->p_flags);
  

• 	goto err;
  

• }
  

• if (j == 0 && flags != (PF_R | PF_W)) {
  

• 	fprintf(stderr,
  

• 		"TCS has invalid segment flags 0x%02x.\n",
  

• 		phdr->p_flags);
  

• 	goto err;
  

• }
  

• if (j == 0) {
  

• 	src_offset = (phdr->p_offset & PAGE_MASK) - src_offset;
  

• 	seg->prot = PROT_READ | PROT_WRITE;
  

• 	seg->flags = SGX_PAGE_TYPE_TCS << 8;
  

• } else  {
  

• 	seg->prot = (phdr->p_flags & PF_R) ? PROT_READ : 0;
  

• 	seg->prot |= (phdr->p_flags & PF_W) ? PROT_WRITE : 0;
  

• 	seg->prot |= (phdr->p_flags & PF_X) ? PROT_EXEC : 0;
  

• 	seg->flags = (SGX_PAGE_TYPE_REG << 8) | seg->prot;
  

• }
  

• seg->offset = (phdr->p_offset & PAGE_MASK) - src_offset;
  

• seg->size = (phdr->p_filesz + PAGE_SIZE - 1) & PAGE_MASK;
  

• printf("0x%016lx 0x%016lx 0x%02x\n", seg->offset, seg->size,
  

•        seg->prot);
  

• j++;
  

• }
• assert(j == encl->nr_segments);
• encl->src = encl->bin + src_offset;
• encl->src_size = encl->segment_tbl[j - 1].offset +

• 	 encl->segment_tbl[j - 1].size;
  

• for (encl->encl_size = 4096; encl->encl_size < encl->src_size; )

• encl->encl_size <<= 1;
  

Something's fishy. That selftest fails with

mmap: Cannot allocate memory

I sprinkled some printfs at this size computation above and here's what it says:

0x00007fdd3b4ca190 0x0000000000002000 0x03 0x00007fdd3b4cc190 0x0000000000001000 0x05 0x00007fdd3b4cd190 0x0000000000003000 0x03 encl_load: encl->nr_segments: 3 encl_load: seg2 offset: 0x7fdd3b4cd190, seg2 size: 12288 encl_load: encl_size: 140737488355328, src_size: 140588159402384 encl_map_area: encl_size: 140737488355328 mmap: Cannot allocate memory

src_size is computed by adding the offset and size of the last segment which is at index 2.

The loop computes encl_size to 0x0000800000000000 then and mmap tries to map double that in encl_map_area(). Looks like too much to me too.

What's up?