111 lines
2.9 KiB
C
111 lines
2.9 KiB
C
|
// SPDX-License-Identifier: GPL-2.0-only
|
||
|
|
/*
|
||
|
|
* memconsole-coreboot.c
|
||
|
|
*
|
||
|
|
* Memory based BIOS console accessed through coreboot table.
|
||
|
|
*
|
||
|
|
* Copyright 2017 Google Inc.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <linux/device.h>
|
||
|
|
#include <linux/io.h>
|
||
|
|
#include <linux/kernel.h>
|
||
|
|
#include <linux/module.h>
|
||
|
|
|
||
|
|
#include "memconsole.h"
|
||
|
|
#include "coreboot_table.h"
|
||
|
|
|
||
|
|
#define CB_TAG_CBMEM_CONSOLE 0x17
|
||
|
|
|
||
|
|
/* CBMEM firmware console log descriptor. */
|
||
|
|
struct cbmem_cons {
|
||
|
|
u32 size_dont_access_after_boot;
|
||
|
|
u32 cursor;
|
||
|
|
u8 body[];
|
||
|
|
} __packed;
|
||
|
|
|
||
|
|
#define CURSOR_MASK ((1 << 28) - 1)
|
||
|
|
#define OVERFLOW (1 << 31)
|
||
|
|
|
||
|
|
static struct cbmem_cons *cbmem_console;
|
||
|
|
static u32 cbmem_console_size;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* The cbmem_console structure is read again on every access because it may
|
||
|
|
* change at any time if runtime firmware logs new messages. This may rarely
|
||
|
|
* lead to race conditions where the firmware overwrites the beginning of the
|
||
|
|
* ring buffer with more lines after we have already read |cursor|. It should be
|
||
|
|
* rare and harmless enough that we don't spend extra effort working around it.
|
||
|
|
*/
|
||
|
|
static ssize_t memconsole_coreboot_read(char *buf, loff_t pos, size_t count)
|
||
|
|
{
|
||
|
|
u32 cursor = cbmem_console->cursor & CURSOR_MASK;
|
||
|
|
u32 flags = cbmem_console->cursor & ~CURSOR_MASK;
|
||
|
|
u32 size = cbmem_console_size;
|
||
|
|
struct seg { /* describes ring buffer segments in logical order */
|
||
|
|
u32 phys; /* physical offset from start of mem buffer */
|
||
|
|
u32 len; /* length of segment */
|
||
|
|
} seg[2] = { {0}, {0} };
|
||
|
|
size_t done = 0;
|
||
|
|
int i;
|
||
|
|
|
||
|
|
if (flags & OVERFLOW) {
|
||
|
|
if (cursor > size) /* Shouldn't really happen, but... */
|
||
|
|
cursor = 0;
|
||
|
|
seg[0] = (struct seg){.phys = cursor, .len = size - cursor};
|
||
|
|
seg[1] = (struct seg){.phys = 0, .len = cursor};
|
||
|
|
} else {
|
||
|
|
seg[0] = (struct seg){.phys = 0, .len = min(cursor, size)};
|
||
|
|
}
|
||
|
|
|
||
|
|
for (i = 0; i < ARRAY_SIZE(seg) && count > done; i++) {
|
||
|
|
done += memory_read_from_buffer(buf + done, count - done, &pos,
|
||
|
|
cbmem_console->body + seg[i].phys, seg[i].len);
|
||
|
|
pos -= seg[i].len;
|
||
|
|
}
|
||
|
|
return done;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int memconsole_probe(struct coreboot_device *dev)
|
||
|
|
{
|
||
|
|
struct cbmem_cons *tmp_cbmc;
|
||
|
|
|
||
|
|
tmp_cbmc = memremap(dev->cbmem_ref.cbmem_addr,
|
||
|
|
sizeof(*tmp_cbmc), MEMREMAP_WB);
|
||
|
|
|
||
|
|
if (!tmp_cbmc)
|
||
|
|
return -ENOMEM;
|
||
|
|
|
||
|
|
/* Read size only once to prevent overrun attack through /dev/mem. */
|
||
|
|
cbmem_console_size = tmp_cbmc->size_dont_access_after_boot;
|
||
|
|
cbmem_console = devm_memremap(&dev->dev, dev->cbmem_ref.cbmem_addr,
|
||
|
|
cbmem_console_size + sizeof(*cbmem_console),
|
||
|
|
MEMREMAP_WB);
|
||
|
|
memunmap(tmp_cbmc);
|
||
|
|
|
||
|
|
if (IS_ERR(cbmem_console))
|
||
|
|
return PTR_ERR(cbmem_console);
|
||
|
|
|
||
|
|
memconsole_setup(memconsole_coreboot_read);
|
||
|
|
|
||
|
|
return memconsole_sysfs_init();
|
||
|
|
}
|
||
|
|
|
||
|
|
static void memconsole_remove(struct coreboot_device *dev)
|
||
|
|
{
|
||
|
|
memconsole_exit();
|
||
|
|
}
|
||
|
|
|
||
|
|
static struct coreboot_driver memconsole_driver = {
|
||
|
|
.probe = memconsole_probe,
|
||
|
|
.remove = memconsole_remove,
|
||
|
|
.drv = {
|
||
|
|
.name = "memconsole",
|
||
|
|
},
|
||
|
|
.tag = CB_TAG_CBMEM_CONSOLE,
|
||
|
|
};
|
||
|
|
module_coreboot_driver(memconsole_driver);
|
||
|
|
|
||
|
|
MODULE_AUTHOR("Google, Inc.");
|
||
|
|
MODULE_LICENSE("GPL");
|