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Kernel/riscv64: Don't clobber the boot info argument in enable_paging
"register asm" variables don't preserve the register value, so the call to calculate_physical_to_link_time_address_offset in the asm input operands is allowed to clobber a0.
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01f1d2daaa
Notes:
sideshowbarker
2024-07-17 11:34:34 +09:00
Author: https://github.com/spholz Commit: https://github.com/SerenityOS/serenity/commit/01f1d2daaa Pull-request: https://github.com/SerenityOS/serenity/pull/24104
@ -177,8 +177,9 @@ static UNMAP_AFTER_INIT void setup_kernel_page_directory(u64* root_table)
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// This function has to fit into one page as it will be identity mapped.
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[[gnu::aligned(PAGE_SIZE)]] [[noreturn]] UNMAP_AFTER_INIT static void enable_paging(BootInfo const& info, FlatPtr satp, u64* enable_paging_pte)
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{
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// Switch current root page table to argument 0. This will immediately take effect, but we won't not crash as this function is identity mapped.
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// Switch current root page table to argument 1. This will immediately take effect, but we won't not crash as this function is identity mapped.
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// Also, set up a temporary trap handler to catch any traps while switching page tables.
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auto offset = calculate_physical_to_link_time_address_offset();
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register FlatPtr a0 asm("a0") = bit_cast<FlatPtr>(&info);
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asm volatile(
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" lla t0, 1f \n"
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@ -213,7 +214,7 @@ static UNMAP_AFTER_INIT void setup_kernel_page_directory(u64* root_table)
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" wfi \n"
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" j 1b \n"
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:
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: "r"(a0), [satp] "r"(satp), [offset] "r"(calculate_physical_to_link_time_address_offset()), [enable_paging_pte] "r"(enable_paging_pte)
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: "r"(a0), [satp] "r"(satp), [offset] "r"(offset), [enable_paging_pte] "r"(enable_paging_pte)
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: "t0");
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VERIFY_NOT_REACHED();
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