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firmware: Support position independent execution

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Enable OpenSBI to support position independent execution. Because the
position independent code will cause an additional GOT reference when
accessing the global variables, it will reduce performance a bit. Therefore,
the position independent execution is disabled by default. Users can
through specifying "FW_PIC=y" on the make command to enable this feature.

In theory, after enabling position-independent execution, the OpenSBI
can run at arbitrary address with appropriate alignment. Therefore, the
original relocation mechanism will be skipped. In other words, OpenSBI will
directly run at the load address without any code movement.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
This commit is contained in:
Vincent Chen
2021-03-17 09:16:38 +08:00
committed by Anup Patel
parent 22d8ee9758
commit 0f20e8adcf
5 changed files with 96 additions and 2 deletions
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14
include/sbi/riscv_elf.h Normal file
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#ifndef __RISCV_ELF_H__
#define __RISCV_ELF_H__
#include <sbi/riscv_asm.h>
#define R_RISCV_32 1
#define R_RISCV_64 2
#define R_RISCV_RELATIVE 3
#define RELOC_TYPE __REG_SEL(R_RISCV_64, R_RISCV_32)
#define SYM_INDEX __REG_SEL(0x20, 0x8)
#define SYM_SIZE __REG_SEL(0x18,0x10)
#endif