From 5ff54a875642962fc857cee00bde17f9a465f1fa Mon Sep 17 00:00:00 2001 From: Bradley Morgan Date: Sun, 4 Oct 2026 10:42:10 +0000 Subject: tashaboot: arm64 bootloader holy shit it's here, Tashaboot, based from arm arm, enjoy reading this masterpiece Signed-off-by: Bradley Morgan --- common/dtb_reloc.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 common/dtb_reloc.c (limited to 'common/dtb_reloc.c') diff --git a/common/dtb_reloc.c b/common/dtb_reloc.c new file mode 100644 index 0000000..c3e0fe5 --- /dev/null +++ b/common/dtb_reloc.c @@ -0,0 +1,69 @@ +/* + * dtb_reloc.c - grow the devicetree the way libfdt does, in a + * buffer with room to spare. firmware cannot edit a packed fdt + * in place, new properties shift everything behind them, so the + * blob is copied into scratch verbatim, the free space after + * totalsize is the room the insert code shifts into, then the + * walkers patch the copy and the kernel gets its address. + * + * The layout follows the devicetree specification: header, + * struct block, strings block, free space. The rebuild copies + * header, struct, strings, fixes the offsets in the new header, + * and leaves the gap between struct and strings as the room new + * properties will consume. + * + * Copyright (C) 2026 Bradley Morgan + */ + +#include +#include +#include +#include + +#define FDT_BEGIN_NODE 1 +#define FDT_END_NODE 2 +#define FDT_PROP 3 +#define FDT_NOP 4 +#define FDT_END 9 + +static uint32_t be32(const void *p) +{ + const uint8_t *b = p; + + return ((uint32_t)b[0] << 24) | ((uint32_t)b[1] << 16) | + ((uint32_t)b[2] << 8) | (uint32_t)b[3]; +} + +/* + * copy the blob into the scratch, grow bytes of headroom after + * the end. returns the new blob address or 0 on a short buffer. + */ +uintptr_t tb_dtb_relocate(uintptr_t dtb, void *scratch, size_t scratch_size, + size_t grow) +{ + uint8_t *in = (uint8_t *)dtb; + uint8_t *out = scratch; + uint32_t totalsize; + + if (be32(in) != 0xd00dfeed) + return 0; + + totalsize = be32(in + 4); + + if (scratch_size < (size_t)totalsize + grow) + return 0; + + /* + * verbatim copy, byte for byte. the grow room is the free + * scratch after totalsize, the insert code shifts the + * strings block into it. an interior gap between the + * struct and strings blocks only invites the walkers to + * count it as tree. + */ + for (uint32_t i = 0; i < totalsize; i++) + out[i] = in[i]; + + (void)grow; + + return (uintptr_t)out; +} -- cgit v1.2.3