53 lines
1.7 KiB
Plaintext
53 lines
1.7 KiB
Plaintext
/* Kernel link layout — higher half.
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*
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* The kernel is linked to *run* in the higher half (virtual base
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* 0xFFFF_FFFF_8000_0000, matching danos.kernel_virt_base and build.zig's
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* image_base) but is *loaded* low. Each section's load address (LMA) is its
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* virtual address minus KERNEL_VIRT_BASE via AT(), so the ELF's p_paddr lands
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* at a low physical address (.text at 1 MiB) that the loader can allocate and
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* copy into. The loader maps p_vaddr (high) -> p_paddr (low) in its bootstrap
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* tables and jumps to the high entry; the kernel then builds its own tables
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* with the physmap and abandons the identity map. Requires LLD (build.zig pins
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* it) — the self-hosted linker ignores PHDRS/AT()/section order.
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*/
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KERNEL_VIRT_BASE = 0xFFFFFFFF80000000;
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ENTRY(_start)
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/* One loadable segment per permission set, so the loader can map .text as R+X,
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* .rodata as R, and .data/.bss as R+W. FLAGS bits: 1=X, 2=W, 4=R. */
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PHDRS {
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text PT_LOAD FLAGS(5); /* R + X */
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rodata PT_LOAD FLAGS(4); /* R */
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data PT_LOAD FLAGS(6); /* R + W */
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}
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SECTIONS {
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.text ALIGN(4K) : AT(ADDR(.text) - KERNEL_VIRT_BASE) {
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*(.text .text.*)
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} :text
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.rodata ALIGN(4K) : AT(ADDR(.rodata) - KERNEL_VIRT_BASE) {
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*(.rodata .rodata.*)
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} :rodata
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.data ALIGN(4K) : AT(ADDR(.data) - KERNEL_VIRT_BASE) {
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*(.data .data.*)
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} :data
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/* .bss occupies memory but not file space. The loader zeroes it via the
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* gap between each PT_LOAD segment's file size and memory size, so no
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* boundary symbols are needed here. */
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.bss ALIGN(4K) : AT(ADDR(.bss) - KERNEL_VIRT_BASE) {
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*(.bss .bss.*)
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*(COMMON)
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} :data
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/DISCARD/ : {
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*(.comment)
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*(.note .note.*)
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*(.eh_frame .eh_frame_hdr)
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}
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}
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