blob: fd04c2e7e257f3d9c92fe249a478ea241fbb0a8a [file] [log] [blame]
/*
* Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <asm_macros.S>
#include <console_macros.S>
#include <drivers/coreboot/cbmem_console.h>
/*
* This driver implements access to coreboot's in-memory console
* (CBMEM console). For the original implementation, see
* <coreboot>/src/lib/cbmem_console.c.
*/
.globl console_cbmc_register
.globl console_cbmc_putc
.globl console_cbmc_flush
/* -----------------------------------------------
* int console_cbmc_register(uintptr_t base,
* console_cbmc_t *console);
* Registers a new CBMEM console instance. Reads
* the size field from the buffer header structure
* and stores it in our console_cbmc_t struct, so
* that we keep the size in secure memory where we
* can trust it. A malicious EL1 could manipulate
* the console buffer (including the header), so we
* must not trust its contents after boot.
* In: x0 - CBMEM console base address
* x1 - pointer to empty console_cbmc_t struct
* Out: x0 - 1 to indicate success
* Clobber list: x0, x1, x2, x7
* -----------------------------------------------
*/
func console_cbmc_register
str x0, [x1, #CONSOLE_T_CBMC_BASE]
ldr w2, [x0]
str w2, [x1, #CONSOLE_T_CBMC_SIZE]
mov x0, x1
finish_console_register cbmc putc=1, flush=1
endfunc console_cbmc_register
/* -----------------------------------------------
* int console_cbmc_puts(int c, console_cbmc_t *console)
* Writes a character to the CBMEM console buffer,
* including overflow handling of the cursor field.
* The character must be preserved in x0.
* In: x0 - character to be stored
* x1 - pointer to console_cbmc_t struct
* Clobber list: x1, x2, x16, x17
* -----------------------------------------------
*/
func console_cbmc_putc
ldr w2, [x1, #CONSOLE_T_CBMC_SIZE]
ldr x1, [x1, #CONSOLE_T_CBMC_BASE]
add x1, x1, #8 /* keep address of body in x1 */
ldr w16, [x1, #-4] /* load cursor (one u32 before body) */
and w17, w16, #0xf0000000 /* keep flags part in w17 */
and w16, w16, #0x0fffffff /* keep actual cursor part in w16 */
cmp w16, w2 /* sanity check that cursor < size */
b.lo putc_within_bounds
mov w0, #-1 /* cursor >= size must be malicious */
ret /* so return error, don't write char */
putc_within_bounds:
strb w0, [x1, w16, uxtw] /* body[cursor] = character */
add w16, w16, #1 /* cursor++ */
cmp w16, w2 /* if cursor < size... */
b.lo putc_write_back /* ...skip overflow handling */
mov w16, #0 /* on overflow, set cursor back to 0 */
orr w17, w17, #(1 << 31) /* and set overflow flag */
putc_write_back:
orr w16, w16, w17 /* merge cursor and flags back */
str w16, [x1, #-4] /* write back cursor to memory */
ret
endfunc console_cbmc_putc
/* -----------------------------------------------
* int console_cbmc_flush(console_cbmc_t *console)
* Flushes the CBMEM console by flushing the
* console buffer from the CPU's data cache.
* In: x0 - pointer to console_cbmc_t struct
* Out: x0 - 0 for success
* Clobber list: x0, x1, x2, x3, x5
* -----------------------------------------------
*/
func console_cbmc_flush
mov x5, x30
ldr x1, [x0, #CONSOLE_T_CBMC_SIZE]
ldr x0, [x0, #CONSOLE_T_CBMC_BASE]
add x1, x1, #8 /* add size of console header */
bl clean_dcache_range /* (clobbers x2 and x3) */
mov x0, #0
ret x5
endfunc console_cbmc_flush