efi/x86: Don't map the entire kernel text RW for mixed mode
The mixed mode thunking routine requires a part of it to be mapped 1:1, and for this reason, we currently map the entire kernel .text read/write in the EFI page tables, which is bad. In fact, the kernel_map_pages_in_pgd() invocation that installs this mapping is entirely redundant, since all of DRAM is already 1:1 mapped read/write in the EFI page tables when we reach this point, which means that .rodata is mapped read-write as well. So let's remap both .text and .rodata read-only in the EFI page tables. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200113172245.27925-6-ardb@kernel.org
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@ -391,11 +391,11 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
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efi_scratch.phys_stack = page_to_phys(page + 1); /* stack grows down */
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npages = (_etext - _text) >> PAGE_SHIFT;
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npages = (__end_rodata_aligned - _text) >> PAGE_SHIFT;
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text = __pa(_text);
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pfn = text >> PAGE_SHIFT;
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pf = _PAGE_RW | _PAGE_ENC;
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pf = _PAGE_ENC;
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if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, pf)) {
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pr_err("Failed to map kernel text 1:1\n");
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return 1;
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