9b583cc539
Add support for the relocation type R_ARM_ARM_THM_CALL which is
produced for the ARM Thumb BL and BLX (branch immediate)
instructions.
These instructions are used for non-static functions like
void test1(void)
{
}
void main(void)
{
test1();
}
Without support for this relocation, test1() has to be static.
Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>
90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
/*
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* Copyright (c) 2023 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/llext/elf.h>
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#include <zephyr/llext/llext.h>
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#include <zephyr/logging/log.h>
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#include <zephyr/sys/util.h>
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LOG_MODULE_REGISTER(elf, CONFIG_LLEXT_LOG_LEVEL);
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#define ARM_BL_BLX_UPPER_S_BIT BIT(10)
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#define ARM_BL_BLX_ADDEND_OFFSET 0
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#define ARM_BL_BLX_ADDEND_SIZE 11
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#define ARM_BL_BLX_ADDEND_MASK 0x7FF
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#define ARM_BL_BLX_HDR_MASK 0xF800
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#define ARM_BL_BLX_LOWER_T1T2_BIT BIT(12)
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static int32_t arm_bl_blx_decode_addend(uintptr_t opaddr)
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{
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uint16_t upper = *((uint16_t *)opaddr);
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uint16_t lower = *(((uint16_t *)opaddr) + 1);
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int32_t addend = upper & ARM_BL_BLX_UPPER_S_BIT ? UINT32_MAX : 0;
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addend <<= ARM_BL_BLX_ADDEND_SIZE;
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addend |= upper & ARM_BL_BLX_ADDEND_MASK;
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addend <<= ARM_BL_BLX_ADDEND_SIZE;
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addend |= lower & ARM_BL_BLX_ADDEND_MASK;
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return lower & ARM_BL_BLX_LOWER_T1T2_BIT ? addend << 1 : addend << 2;
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}
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static void arm_bl_blx_encode_addend(uintptr_t opaddr, int32_t addend)
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{
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uint16_t upper = *((uint16_t *)opaddr);
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uint16_t lower = *(((uint16_t *)opaddr) + 1);
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addend = upper & ARM_BL_BLX_UPPER_S_BIT ? addend >> 1 : addend >> 2;
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upper &= ARM_BL_BLX_HDR_MASK;
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lower &= ARM_BL_BLX_HDR_MASK;
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upper |= (addend >> ARM_BL_BLX_ADDEND_SIZE) & ARM_BL_BLX_ADDEND_MASK;
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lower |= addend & ARM_BL_BLX_ADDEND_MASK;
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*((uint16_t *)opaddr) = upper;
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*(((uint16_t *)opaddr) + 1) = lower;
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}
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/**
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* @brief Architecture specific function for relocating partially linked (static) elf
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*
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* Elf files contain a series of relocations described in a section. These relocation
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* instructions are architecture specific and each architecture supporting extensions
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* must implement this.
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*
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* The relocation codes for arm are well documented
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* https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst#relocation
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*/
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void arch_elf_relocate(elf_rela_t *rel, uintptr_t opaddr, uintptr_t opval)
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{
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elf_word reloc_type = ELF32_R_TYPE(rel->r_info);
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switch (reloc_type) {
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case R_ARM_ABS32:
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/* Add the addend stored at opaddr to opval */
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opval += *((uint32_t *)opaddr);
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/* Update the absolute address of a load/store instruction */
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*((uint32_t *)opaddr) = (uint32_t)opval;
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break;
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case R_ARM_THM_CALL:
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/* Decode the initial addend */
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int32_t addend = arm_bl_blx_decode_addend(opaddr);
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/* Calculate and add the branch offset (addend) */
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addend += ((int32_t)opval) - ((int32_t)opaddr);
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/* Encode the addend */
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arm_bl_blx_encode_addend(opaddr, addend);
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break;
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default:
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LOG_DBG("Unsupported ARM elf relocation type %d at address %lx",
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reloc_type, opaddr);
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break;
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}
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}
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