1 files changed, 164 insertions, 0 deletions
diff --git a/arch/mips/lib/reloc.c b/arch/mips/lib/reloc.c
new file mode 100644
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+++ b/arch/mips/lib/reloc.c
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+/*
+ * MIPS Relocation
+ *
+ * Copyright (c) 2017 Imagination Technologies Ltd.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ *
+ * Relocation data, found in the .rel section, is generated by the mips-relocs
+ * tool & contains a record of all locations in the U-Boot binary that need to
+ * be fixed up during relocation.
+ *
+ * The data is a sequence of unsigned integers, which are of somewhat arbitrary
+ * size. This is achieved by encoding integers as a sequence of bytes, each of
+ * which contains 7 bits of data with the most significant bit indicating
+ * whether any further bytes need to be read. The least significant bits of the
+ * integer are found in the first byte - ie. it somewhat resembles little
+ * endian.
+ *
+ * Each pair of two integers represents a relocation that must be applied. The
+ * first integer represents the type of relocation as a standard ELF relocation
+ * type (ie. R_MIPS_*). The second integer represents the offset at which to
+ * apply the relocation, relative to the previous relocation or for the first
+ * relocation the start of the relocated .text section.
+ *
+ * The end of the relocation data is indicated when type R_MIPS_NONE (0) is
+ * read, at which point no further integers should be read. That is, the
+ * terminating R_MIPS_NONE reloc includes no offset.
+ */
+
+#include <common.h>
+#include <asm/relocs.h>
+#include <asm/sections.h>
+
+/**
+ * read_uint() - Read an unsigned integer from the buffer
+ * @buf: pointer to a pointer to the reloc buffer
+ *
+ * Read one whole unsigned integer from the relocation data pointed to by @buf,
+ * advancing @buf past the bytes encoding the integer.
+ *
+ * Returns: the integer read from @buf
+ */
+static unsigned long read_uint(uint8_t **buf)
+{
+	unsigned long val = 0;
+	unsigned int shift = 0;
+	uint8_t new;
+
+	do {
+		new = *(*buf)++;
+		val |= (new & 0x7f) << shift;
+		shift += 7;
+	} while (new & 0x80);
+
+	return val;
+}
+
+/**
+ * apply_reloc() - Apply a single relocation
+ * @type: the type of reloc (R_MIPS_*)
+ * @addr: the address that the reloc should be applied to
+ * @off: the relocation offset, ie. number of bytes we're moving U-Boot by
+ *
+ * Apply a single relocation of type @type at @addr. This function is
+ * intentionally simple, and does the bare minimum needed to fixup the
+ * relocated U-Boot - in particular, it does not check for overflows.
+ */
+static void apply_reloc(unsigned int type, void *addr, long off)
+{
+	uint32_t u32;
+
+	switch (type) {
+	case R_MIPS_26:
+		u32 = *(uint32_t *)addr;
+		u32 = (u32 & GENMASK(31, 26)) |
+		      ((u32 + (off >> 2)) & GENMASK(25, 0));
+		*(uint32_t *)addr = u32;
+		break;
+
+	case R_MIPS_32:
+		*(uint32_t *)addr += off;
+		break;
+
+	case R_MIPS_64:
+		*(uint64_t *)addr += off;
+		break;
+
+	case R_MIPS_HI16:
+		*(uint32_t *)addr += off >> 16;
+		break;
+
+	default:
+		panic("Unhandled reloc type %u\n", type);
+	}
+}
+
+/**
+ * relocate_code() - Relocate U-Boot, generally from flash to DDR
+ * @start_addr_sp: new stack pointer
+ * @new_gd: pointer to relocated global data
+ * @relocaddr: the address to relocate to
+ *
+ * Relocate U-Boot from its current location (generally in flash) to a new one
+ * (generally in DDR). This function will copy the U-Boot binary & apply
+ * relocations as necessary, then jump to board_init_r in the new build of
+ * U-Boot. As such, this function does not return.
+ */
+void relocate_code(ulong start_addr_sp, gd_t *new_gd, ulong relocaddr)
+{
+	unsigned long addr, length, bss_len;
+	uint8_t *buf, *bss_start;
+	unsigned int type;
+	long off;
+
+	/*
+	 * Ensure that we're relocating by an offset which is a multiple of
+	 * 64KiB, ie. doesn't change the least significant 16 bits of any
+	 * addresses. This allows us to discard R_MIPS_LO16 relocs, saving
+	 * space in the U-Boot binary & complexity in handling them.
+	 */
+	off = relocaddr - (unsigned long)__text_start;
+	if (off & 0xffff)
+		panic("Mis-aligned relocation\n");
+
+	/* Copy U-Boot to RAM */
+	length = __image_copy_end - __text_start;
+	memcpy((void *)relocaddr, __text_start, length);
+
+	/* Now apply relocations to the copy in RAM */
+	buf = __rel_start;
+	addr = relocaddr;
+	while (true) {
+		type = read_uint(&buf);
+		if (type == R_MIPS_NONE)
+			break;
+
+		addr += read_uint(&buf) << 2;
+		apply_reloc(type, (void *)addr, off);
+	}
+
+	/* Ensure the icache is coherent */
+	flush_cache(relocaddr, length);
+
+	/* Clear the .bss section */
+	bss_start = (uint8_t *)((unsigned long)__bss_start + off);
+	bss_len = (unsigned long)&__bss_end - (unsigned long)__bss_start;
+	memset(bss_start, 0, bss_len);
+
+	/* Jump to the relocated U-Boot */
+	asm volatile(
+		       "move	$29, %0\n"
+		"	move	$4, %1\n"
+		"	move	$5, %2\n"
+		"	move	$31, $0\n"
+		"	jr	%3"
+		: /* no outputs */
+		: "r"(start_addr_sp),
+		  "r"(new_gd),
+		  "r"(relocaddr),
+		  "r"((unsigned long)board_init_r + off));
+
+	/* Since we jumped to the new U-Boot above, we won't get here */
+	unreachable();
+}