diff options
Diffstat (limited to '')
| -rw-r--r-- | lib/aarch32/misc_helpers.S | 315 |
1 files changed, 315 insertions, 0 deletions
diff --git a/lib/aarch32/misc_helpers.S b/lib/aarch32/misc_helpers.S new file mode 100644 index 0000000..59e15bd --- /dev/null +++ b/lib/aarch32/misc_helpers.S @@ -0,0 +1,315 @@ +/* + * Copyright (c) 2016-2021, ARM Limited and Contributors. All rights reserved. + * + * SPDX-License-Identifier: BSD-3-Clause + */ + +#include <arch.h> +#include <asm_macros.S> +#include <assert_macros.S> +#include <common/bl_common.h> +#include <lib/xlat_tables/xlat_tables_defs.h> + + .globl smc + .globl zeromem + .globl zero_normalmem + .globl memcpy4 + .globl disable_mmu_icache_secure + .globl disable_mmu_secure + .globl fixup_gdt_reloc + +#define PAGE_START_MASK ~(PAGE_SIZE_MASK) + +func smc + /* + * For AArch32 only r0-r3 will be in the registers; + * rest r4-r6 will be pushed on to the stack. So here, we'll + * have to load them from the stack to registers r4-r6 explicitly. + * Clobbers: r4-r6 + */ + ldm sp, {r4, r5, r6} + smc #0 +endfunc smc + +/* ----------------------------------------------------------------------- + * void zeromem(void *mem, unsigned int length) + * + * Initialise a region in normal memory to 0. This functions complies with the + * AAPCS and can be called from C code. + * + * ----------------------------------------------------------------------- + */ +func zeromem + /* + * Readable names for registers + * + * Registers r0, r1 and r2 are also set by zeromem which + * branches into the fallback path directly, so cursor, length and + * stop_address should not be retargeted to other registers. + */ + cursor .req r0 /* Start address and then current address */ + length .req r1 /* Length in bytes of the region to zero out */ + /* + * Reusing the r1 register as length is only used at the beginning of + * the function. + */ + stop_address .req r1 /* Address past the last zeroed byte */ + zeroreg1 .req r2 /* Source register filled with 0 */ + zeroreg2 .req r3 /* Source register filled with 0 */ + tmp .req r12 /* Temporary scratch register */ + + mov zeroreg1, #0 + + /* stop_address is the address past the last to zero */ + add stop_address, cursor, length + + /* + * Length cannot be used anymore as it shares the same register with + * stop_address. + */ + .unreq length + + /* + * If the start address is already aligned to 8 bytes, skip this loop. + */ + tst cursor, #(8-1) + beq .Lzeromem_8bytes_aligned + + /* Calculate the next address aligned to 8 bytes */ + orr tmp, cursor, #(8-1) + adds tmp, tmp, #1 + /* If it overflows, fallback to byte per byte zeroing */ + beq .Lzeromem_1byte_aligned + /* If the next aligned address is after the stop address, fall back */ + cmp tmp, stop_address + bhs .Lzeromem_1byte_aligned + + /* zero byte per byte */ +1: + strb zeroreg1, [cursor], #1 + cmp cursor, tmp + bne 1b + + /* zero 8 bytes at a time */ +.Lzeromem_8bytes_aligned: + + /* Calculate the last 8 bytes aligned address. */ + bic tmp, stop_address, #(8-1) + + cmp cursor, tmp + bhs 2f + + mov zeroreg2, #0 +1: + stmia cursor!, {zeroreg1, zeroreg2} + cmp cursor, tmp + blo 1b +2: + + /* zero byte per byte */ +.Lzeromem_1byte_aligned: + cmp cursor, stop_address + beq 2f +1: + strb zeroreg1, [cursor], #1 + cmp cursor, stop_address + bne 1b +2: + bx lr + + .unreq cursor + /* + * length is already unreq'ed to reuse the register for another + * variable. + */ + .unreq stop_address + .unreq zeroreg1 + .unreq zeroreg2 + .unreq tmp +endfunc zeromem + +/* + * AArch32 does not have special ways of zeroing normal memory as AArch64 does + * using the DC ZVA instruction, so we just alias zero_normalmem to zeromem. + */ +.equ zero_normalmem, zeromem + +/* -------------------------------------------------------------------------- + * void memcpy4(void *dest, const void *src, unsigned int length) + * + * Copy length bytes from memory area src to memory area dest. + * The memory areas should not overlap. + * Destination and source addresses must be 4-byte aligned. + * -------------------------------------------------------------------------- + */ +func memcpy4 +#if ENABLE_ASSERTIONS + orr r3, r0, r1 + tst r3, #0x3 + ASM_ASSERT(eq) +#endif +/* copy 4 bytes at a time */ +m_loop4: + cmp r2, #4 + blo m_loop1 + ldr r3, [r1], #4 + str r3, [r0], #4 + subs r2, r2, #4 + bne m_loop4 + bx lr + +/* copy byte per byte */ +m_loop1: + ldrb r3, [r1], #1 + strb r3, [r0], #1 + subs r2, r2, #1 + bne m_loop1 + bx lr +endfunc memcpy4 + +/* --------------------------------------------------------------------------- + * Disable the MMU in Secure State + * --------------------------------------------------------------------------- + */ + +func disable_mmu_secure + mov r1, #(SCTLR_M_BIT | SCTLR_C_BIT) +do_disable_mmu: +#if ERRATA_A9_794073 + stcopr r0, BPIALL + dsb +#endif + ldcopr r0, SCTLR + bic r0, r0, r1 + stcopr r0, SCTLR + isb // ensure MMU is off + dsb sy + bx lr +endfunc disable_mmu_secure + + +func disable_mmu_icache_secure + ldr r1, =(SCTLR_M_BIT | SCTLR_C_BIT | SCTLR_I_BIT) + b do_disable_mmu +endfunc disable_mmu_icache_secure + +/* --------------------------------------------------------------------------- + * Helper to fixup Global Descriptor table (GDT) and dynamic relocations + * (.rel.dyn) at runtime. + * + * This function is meant to be used when the firmware is compiled with -fpie + * and linked with -pie options. We rely on the linker script exporting + * appropriate markers for start and end of the section. For GOT, we + * expect __GOT_START__ and __GOT_END__. Similarly for .rela.dyn, we expect + * __RELA_START__ and __RELA_END__. + * + * The function takes the limits of the memory to apply fixups to as + * arguments (which is usually the limits of the relocable BL image). + * r0 - the start of the fixup region + * r1 - the limit of the fixup region + * These addresses have to be 4KB page aligned. + * --------------------------------------------------------------------------- + */ + +/* Relocation codes */ +#define R_ARM_RELATIVE 23 + +func fixup_gdt_reloc + mov r6, r0 + mov r7, r1 + +#if ENABLE_ASSERTIONS + /* Test if the limits are 4K aligned */ + orr r0, r0, r1 + mov r1, #(PAGE_SIZE_MASK) + tst r0, r1 + ASM_ASSERT(eq) +#endif + /* + * Calculate the offset based on return address in lr. + * Assume that this function is called within a page at the start of + * fixup region. + */ + ldr r1, =PAGE_START_MASK + and r2, lr, r1 + subs r0, r2, r6 /* Diff(S) = Current Address - Compiled Address */ + beq 3f /* Diff(S) = 0. No relocation needed */ + + ldr r1, =__GOT_START__ + add r1, r1, r0 + ldr r2, =__GOT_END__ + add r2, r2, r0 + + /* + * GOT is an array of 32_bit addresses which must be fixed up as + * new_addr = old_addr + Diff(S). + * The new_addr is the address currently the binary is executing from + * and old_addr is the address at compile time. + */ +1: ldr r3, [r1] + + /* Skip adding offset if address is < lower limit */ + cmp r3, r6 + blo 2f + + /* Skip adding offset if address is > upper limit */ + cmp r3, r7 + bhi 2f + add r3, r3, r0 + str r3, [r1] + +2: add r1, r1, #4 + cmp r1, r2 + blo 1b + + /* Starting dynamic relocations. Use ldr to get RELA_START and END */ +3: ldr r1, =__RELA_START__ + add r1, r1, r0 + ldr r2, =__RELA_END__ + add r2, r2, r0 + + /* + * According to ELF-32 specification, the RELA data structure is as + * follows: + * typedef struct { + * Elf32_Addr r_offset; + * Elf32_Xword r_info; + * } Elf32_Rela; + * + * r_offset is address of reference + * r_info is symbol index and type of relocation (in this case + * code 23 which corresponds to R_ARM_RELATIVE). + * + * Size of Elf32_Rela structure is 8 bytes. + */ + + /* Skip R_ARM_NONE entry with code 0 */ +1: ldr r3, [r1, #4] + ands r3, r3, #0xff + beq 2f + +#if ENABLE_ASSERTIONS + /* Assert that the relocation type is R_ARM_RELATIVE */ + cmp r3, #R_ARM_RELATIVE + ASM_ASSERT(eq) +#endif + ldr r3, [r1] /* r_offset */ + add r3, r0, r3 /* Diff(S) + r_offset */ + ldr r4, [r3] + + /* Skip adding offset if address is < lower limit */ + cmp r4, r6 + blo 2f + + /* Skip adding offset if address is > upper limit */ + cmp r4, r7 + bhi 2f + + add r4, r0, r4 + str r4, [r3] + +2: add r1, r1, #8 + cmp r1, r2 + blo 1b + bx lr +endfunc fixup_gdt_reloc |