| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | /* |
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| 3 | * Today's hack: quantum tunneling in structs |
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| 4 | * |
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| 5 | * 'entries' and 'term' are never anywhere referenced by word in code. In fact, |
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| 6 | * they serve as the hanging-off data accessed through repl.data[]. |
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| 7 | */ |
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| 8 | |
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| 9 | /* tbl has the following structure equivalent, but is C99 compliant: |
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| 10 | * struct { |
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| 11 | * struct type##_replace repl; |
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| 12 | * struct type##_standard entries[nhooks]; |
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| 13 | * struct type##_error term; |
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| 14 | * } *tbl; |
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| 15 | */ |
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| 16 | |
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| 17 | #define xt_alloc_initial_table(type, typ2) ({ \ |
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| 18 | unsigned int hook_mask = info->valid_hooks; \ |
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| 19 | unsigned int nhooks = hweight32(hook_mask); \ |
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| 20 | unsigned int bytes = 0, hooknum = 0, i = 0; \ |
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| 21 | struct { \ |
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| 22 | struct type##_replace repl; \ |
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| 23 | struct type##_standard entries[]; \ |
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| 24 | } *tbl; \ |
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| 25 | struct type##_error *term; \ |
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| 26 | size_t term_offset = (offsetof(typeof(*tbl), entries[nhooks]) + \ |
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| 27 | __alignof__(*term) - 1) & ~(__alignof__(*term) - 1); \ |
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| 28 | tbl = kzalloc(term_offset + sizeof(*term), GFP_KERNEL); \ |
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| 29 | if (tbl == NULL) \ |
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| 30 | return NULL; \ |
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| 31 | term = (struct type##_error *)&(((char *)tbl)[term_offset]); \ |
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| 32 | strscpy_pad(tbl->repl.name, info->name, sizeof(tbl->repl.name)); \ |
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| 33 | *term = (struct type##_error)typ2##_ERROR_INIT; \ |
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| 34 | tbl->repl.valid_hooks = hook_mask; \ |
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| 35 | tbl->repl.num_entries = nhooks + 1; \ |
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| 36 | tbl->repl.size = nhooks * sizeof(struct type##_standard) + \ |
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| 37 | sizeof(struct type##_error); \ |
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| 38 | for (; hook_mask != 0; hook_mask >>= 1, ++hooknum) { \ |
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| 39 | if (!(hook_mask & 1)) \ |
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| 40 | continue; \ |
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| 41 | tbl->repl.hook_entry[hooknum] = bytes; \ |
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| 42 | tbl->repl.underflow[hooknum] = bytes; \ |
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| 43 | tbl->entries[i++] = (struct type##_standard) \ |
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| 44 | typ2##_STANDARD_INIT(NF_ACCEPT); \ |
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| 45 | bytes += sizeof(struct type##_standard); \ |
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| 46 | } \ |
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| 47 | tbl; \ |
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| 48 | }) |
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| 49 | |
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