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// SPDX-License-Identifier: GPL-2.0+
/*
* MIPS Relocation
*
* Copyright (c) 2017 Imagination Technologies Ltd.
*
* 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 <cpu_func.h>
#include <init.h>
#include <asm/relocs.h>
#include <asm/sections.h>
#include <linux/bitops.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, uint8_t *buf)
{
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 (@ %p), bss used before relocation?\n",
type, buf);
}
}
/**
* 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, buf);
}
/* 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();
}
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