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f393a76176
Recent OVMF versions (edk2-stable202508 + newer) can write their debug log to a memory buffer. This driver exposes the log content via sysfs (/sys/firmware/efi/ovmf_debug_log). Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
112 lines
2.5 KiB
C
112 lines
2.5 KiB
C
// 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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