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ARM: ensure the signal page contains defined contents
Ensure that the signal page contains our poison instruction to increase the protection against ROP attacks and also contains well defined contents. Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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1 changed files with 8 additions and 6 deletions
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@ -693,18 +693,20 @@ struct page *get_signal_page(void)
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addr = page_address(page);
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/* Poison the entire page */
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memset32(addr, __opcode_to_mem_arm(0xe7fddef1),
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PAGE_SIZE / sizeof(u32));
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/* Give the signal return code some randomness */
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offset = 0x200 + (get_random_int() & 0x7fc);
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signal_return_offset = offset;
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/*
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* Copy signal return handlers into the vector page, and
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* set sigreturn to be a pointer to these.
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*/
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/* Copy signal return handlers into the page */
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memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
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ptr = (unsigned long)addr + offset;
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flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
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/* Flush out all instructions in this page */
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ptr = (unsigned long)addr;
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flush_icache_range(ptr, ptr + PAGE_SIZE);
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return page;
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}
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