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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/drivers/firmware/efi/ovmf-debug-log.c
26428 views
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// SPDX-License-Identifier: GPL-2.0

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#include <linux/efi.h>

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#include <linux/init.h>

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#include <linux/io.h>

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#include <linux/kernel.h>

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#include <linux/kobject.h>

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#include <linux/module.h>

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#include <linux/platform_device.h>

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#include <linux/sysfs.h>

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#define OVMF_DEBUG_LOG_MAGIC1  0x3167646d666d766f  // "ovmfmdg1"

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#define OVMF_DEBUG_LOG_MAGIC2  0x3267646d666d766f  // "ovmfmdg2"

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struct ovmf_debug_log_header {

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	u64    magic1;

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	u64    magic2;

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	u64    hdr_size;

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	u64    log_size;

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	u64    lock; // edk2 spinlock

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	u64    head_off;

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	u64    tail_off;

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	u64    truncated;

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	u8     fw_version[128];

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};

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static struct ovmf_debug_log_header *hdr;

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static u8 *logbuf;

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static u64 logbufsize;

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static ssize_t ovmf_log_read(struct file *filp, struct kobject *kobj,

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			     const struct bin_attribute *attr, char *buf,

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			     loff_t offset, size_t count)

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{

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	u64 start, end;

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	start = hdr->head_off + offset;

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	if (hdr->head_off > hdr->tail_off && start >= hdr->log_size)

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		start -= hdr->log_size;

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	end = start + count;

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	if (start > hdr->tail_off) {

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		if (end > hdr->log_size)

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			end = hdr->log_size;

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	} else {

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		if (end > hdr->tail_off)

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			end = hdr->tail_off;

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	}

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	if (start > logbufsize || end > logbufsize)

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		return 0;

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	if (start >= end)

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		return 0;

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	memcpy(buf, logbuf + start, end - start);

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	return end - start;

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}

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static struct bin_attribute ovmf_log_bin_attr = {

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	.attr = {

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		.name = "ovmf_debug_log",

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		.mode = 0444,

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	},

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	.read = ovmf_log_read,

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};

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int __init ovmf_log_probe(unsigned long ovmf_debug_log_table)

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{

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	int ret = -EINVAL;

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	u64 size;

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	/* map + verify header */

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	hdr = memremap(ovmf_debug_log_table, sizeof(*hdr), MEMREMAP_WB);

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	if (!hdr) {

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		pr_err("OVMF debug log: header map failed\n");

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		return -EINVAL;

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	}

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	if (hdr->magic1 != OVMF_DEBUG_LOG_MAGIC1 ||

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	    hdr->magic2 != OVMF_DEBUG_LOG_MAGIC2) {

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		printk(KERN_ERR "OVMF debug log: magic mismatch\n");

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		goto err_unmap;

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	}

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	size = hdr->hdr_size + hdr->log_size;

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	pr_info("OVMF debug log: firmware version: \"%s\"\n", hdr->fw_version);

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	pr_info("OVMF debug log: buffer size: %lluk\n", size / 1024);

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	/* map complete log buffer */

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	memunmap(hdr);

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	hdr = memremap(ovmf_debug_log_table, size, MEMREMAP_WB);

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	if (!hdr) {

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		pr_err("OVMF debug log: buffer map failed\n");

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		return -EINVAL;

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	}

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	logbuf = (void *)hdr + hdr->hdr_size;

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	logbufsize = hdr->log_size;

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	ovmf_log_bin_attr.size = size;

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	ret = sysfs_create_bin_file(efi_kobj, &ovmf_log_bin_attr);

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	if (ret != 0) {

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		pr_err("OVMF debug log: sysfs register failed\n");

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		goto err_unmap;

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	}

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	return 0;

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err_unmap:

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	memunmap(hdr);

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	return ret;

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}

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