From nobody Tue Oct 7 16:35:43 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EF7892BE026 for ; Tue, 8 Jul 2025 10:56:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751972170; cv=none; b=WIAWhkPvEXrbmsyIrAgVpeyiIPUipEpI5wHun7MI4ZOTQ8EpTAA+PVfC1x3a0GSwtzJDM1xRgzvWhmZJAwxHjHcha0x2kr2mlF8S8cNQVYEHZX6AZk1VIR/4+IaUYci4uynIfZHWz0Wy5TB8rMLJy5ncEAQdOuC1/ZH4LRLSi70= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751972170; c=relaxed/simple; bh=GcH5y9I+vwLgEQFHzGMrRHmf1LUNk+VNdMsUyN/XRd0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=tsxEpuEfkaPE3oEXgHnGmnAkAuGOBMvU/WEs89GtT6SGbEGCIctcNXiPMRajJoE2pXDxYzaChnVNZGlTD+u1RySduXy50E0x9cvGoveMSn65UG5m/XEM8P7hrM1QZMTWmWHy977F2jXsI0PUeeeIWfyplmteCh9fyg+DQQaqLN4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Jt6KXUMW; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Jt6KXUMW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751972167; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=bHrF+We+xHosy6K4Q3pHkoPGMQwoIqcnCH+g8ghgZSQ=; b=Jt6KXUMWeb7z9+B0p49yQBrRiIBLCb5EPUCTJK7E5L6twDDORJ46YRKBCJPfnYFmNbaML/ PtXKJwQ5/waxKxeLZtBkjmlZOvrpnBQOn2WpKdIi/rSirFyiX4pBqRLTsjCFW/ZOKaWJLH 1qOngq/86gyePmJZAN+yGxTkVMomHEs= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-349-4K51PU0BPSGE5dvP52eUYw-1; Tue, 08 Jul 2025 06:56:04 -0400 X-MC-Unique: 4K51PU0BPSGE5dvP52eUYw-1 X-Mimecast-MFC-AGG-ID: 4K51PU0BPSGE5dvP52eUYw_1751972163 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 61ECB195F170; Tue, 8 Jul 2025 10:56:03 +0000 (UTC) Received: from sirius.home.kraxel.org (unknown [10.45.224.100]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 58F5C18002B6; Tue, 8 Jul 2025 10:56:02 +0000 (UTC) Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id AF59918000B2; Tue, 08 Jul 2025 12:55:59 +0200 (CEST) From: Gerd Hoffmann To: linux-efi@vger.kernel.org Cc: Gerd Hoffmann , Ard Biesheuvel , linux-kernel@vger.kernel.org (open list) Subject: [PATCH] efi: add ovmf debug log driver Date: Tue, 8 Jul 2025 12:55:56 +0200 Message-ID: <20250708105559.603425-1-kraxel@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" 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 --- include/linux/efi.h | 2 + drivers/firmware/efi/efi.c | 11 +++ drivers/firmware/efi/ovmf-log.c | 136 ++++++++++++++++++++++++++++++++ drivers/firmware/efi/Kconfig | 9 +++ drivers/firmware/efi/Makefile | 1 + 5 files changed, 159 insertions(+) create mode 100644 drivers/firmware/efi/ovmf-log.c diff --git a/include/linux/efi.h b/include/linux/efi.h index 7d63d1d75f22..55479cd8438b 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -439,6 +439,7 @@ void efi_native_runtime_setup(void); =20 /* OVMF protocol GUIDs */ #define OVMF_SEV_MEMORY_ACCEPTANCE_PROTOCOL_GUID EFI_GUID(0xc5a010fe, 0x38= a7, 0x4531, 0x8a, 0x4a, 0x05, 0x00, 0xd2, 0xfd, 0x16, 0x49) +#define OVMF_MEMORY_LOG_TABLE_GUID EFI_GUID(0x95305139, 0xb20f, 0x4723, = 0x84, 0x25, 0x62, 0x7c, 0x88, 0x8f, 0xf1, 0x21) =20 typedef struct { efi_guid_t guid; @@ -642,6 +643,7 @@ extern struct efi { unsigned long esrt; /* ESRT table */ unsigned long tpm_log; /* TPM2 Event Log table */ unsigned long tpm_final_log; /* TPM2 Final Events Log table */ + unsigned long ovmf_debug_log; unsigned long mokvar_table; /* MOK variable config table */ unsigned long coco_secret; /* Confidential computing secret table */ unsigned long unaccepted; /* Unaccepted memory table */ diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index e57bff702b5f..629a42e50b57 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -45,6 +45,9 @@ struct efi __read_mostly efi =3D { .esrt =3D EFI_INVALID_TABLE_ADDR, .tpm_log =3D EFI_INVALID_TABLE_ADDR, .tpm_final_log =3D EFI_INVALID_TABLE_ADDR, +#ifdef CONFIG_OVMF_DEBUG_LOG + .ovmf_debug_log =3D EFI_INVALID_TABLE_ADDR, +#endif #ifdef CONFIG_LOAD_UEFI_KEYS .mokvar_table =3D EFI_INVALID_TABLE_ADDR, #endif @@ -473,6 +476,11 @@ static int __init efisubsys_init(void) platform_device_register_simple("efi_secret", 0, NULL, 0); #endif =20 +#ifdef CONFIG_OVMF_DEBUG_LOG + if (efi.ovmf_debug_log !=3D EFI_INVALID_TABLE_ADDR) + platform_device_register_simple("ovmf_log", 0, NULL, 0); +#endif + return 0; =20 err_remove_group: @@ -617,6 +625,9 @@ static const efi_config_table_type_t common_tables[] __= initconst =3D { {LINUX_EFI_MEMRESERVE_TABLE_GUID, &mem_reserve, "MEMRESERVE" }, {LINUX_EFI_INITRD_MEDIA_GUID, &initrd, "INITRD" }, {EFI_RT_PROPERTIES_TABLE_GUID, &rt_prop, "RTPROP" }, +#ifdef CONFIG_OVMF_DEBUG_LOG + {OVMF_MEMORY_LOG_TABLE_GUID, &efi.ovmf_debug_log, "OVMF-LOG" }, +#endif #ifdef CONFIG_EFI_RCI2_TABLE {DELLEMC_EFI_RCI2_TABLE_GUID, &rci2_table_phys }, #endif diff --git a/drivers/firmware/efi/ovmf-log.c b/drivers/firmware/efi/ovmf-lo= g.c new file mode 100644 index 000000000000..4af52adb57cc --- /dev/null +++ b/drivers/firmware/efi/ovmf-log.c @@ -0,0 +1,136 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include +#include + +#define MEM_DEBUG_LOG_MAGIC1 0x3167646d666d766f // "ovmfmdg1" +#define MEM_DEBUG_LOG_MAGIC2 0x3267646d666d766f // "ovmfmdg2" + +struct mem_debug_log_header { + u64 magic1; + u64 magic2; + u64 hdr_size; + u64 log_size; + u64 lock; // edk2 spinlock + u64 head_off; + u64 tail_off; + u64 truncated; + u8 fw_version[128]; +}; + +static struct mem_debug_log_header *hdr; +static u8 *logbuf; +static u64 logbufsize; + +static ssize_t ovmf_log_read(struct file *filp, struct kobject *kobj, + const struct bin_attribute *attr, char *buf, + loff_t offset, size_t count) +{ + u64 start, end; + + start =3D hdr->head_off + offset; + if (hdr->head_off > hdr->tail_off && start >=3D hdr->log_size) + start -=3D hdr->log_size; + + end =3D start + count; + if (start > hdr->tail_off) { + if (end > hdr->log_size) + end =3D hdr->log_size; + } else { + if (end > hdr->tail_off) + end =3D hdr->tail_off; + } + + if (start > logbufsize || end > logbufsize) + return 0; + if (start >=3D end) + return 0; + + memcpy(buf, logbuf + start, end - start); + return end - start; +} + +static struct bin_attribute ovmf_log_bin_attr =3D { + .attr =3D { + .name =3D "ovmf_debug_log", + .mode =3D 0444, + }, + .read =3D ovmf_log_read, +}; + +static int ovmf_log_probe(struct platform_device *dev) +{ + u64 size; + int ret =3D -EINVAL; + + if (efi.ovmf_debug_log =3D=3D EFI_INVALID_TABLE_ADDR) { + dev_err(&dev->dev, "OVMF debug log: not available\n"); + return -EINVAL; + } + + /* map + verify header */ + hdr =3D memremap(efi.ovmf_debug_log, sizeof(*hdr), MEMREMAP_WB); + if (!hdr) { + dev_err(&dev->dev, "OVMF debug log: header map failed\n"); + return -EINVAL; + } + + if (hdr->magic1 !=3D MEM_DEBUG_LOG_MAGIC1 || + hdr->magic2 !=3D MEM_DEBUG_LOG_MAGIC2) { + dev_err(&dev->dev, "OVMF debug log: magic mismatch\n"); + goto err_unmap; + } + + size =3D hdr->hdr_size + hdr->log_size; + dev_info(&dev->dev, "firmware version: \"%s\"\n", hdr->fw_version); + dev_info(&dev->dev, "log buffer size: %lldk\n", size / 1024); + + /* map complete log buffer */ + iounmap(hdr); + hdr =3D memremap(efi.ovmf_debug_log, size, MEMREMAP_WB); + if (!hdr) { + dev_err(&dev->dev, "OVMF debug log: buffer map failed\n"); + return -EINVAL; + } + logbuf =3D (void*)hdr + hdr->hdr_size; + logbufsize =3D hdr->log_size; + + ovmf_log_bin_attr.size =3D size; + ret =3D sysfs_create_bin_file(efi_kobj, &ovmf_log_bin_attr); + if (ret !=3D 0) { + dev_err(&dev->dev, "OVMF debug log: sysfs register failed\n"); + goto err_unmap; + } + + return 0; + +err_unmap: + iounmap(hdr); + return ret; +} + +static void ovmf_log_remove(struct platform_device *dev) +{ + iounmap(hdr); +} + +static struct platform_driver ovmf_log_driver =3D { + .probe =3D ovmf_log_probe, + .remove =3D ovmf_log_remove, + .driver =3D { + .name =3D "ovmf_log", + }, +}; + +module_platform_driver(ovmf_log_driver); + +MODULE_DESCRIPTION("OVMF debug log"); +MODULE_AUTHOR("Gerd Hoffmann "); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ovmf_log"); diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index db8c5c03d3a2..4563d0df170f 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -263,6 +263,15 @@ config EFI_COCO_SECRET virt/coco/efi_secret module to access the secrets, which in turn allows userspace programs to access the injected secrets. =20 +config OVMF_DEBUG_LOG + tristate "Expose OVMF firmware debug log via sysfs" + depends on EFI + default y + help + 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). + config UNACCEPTED_MEMORY bool depends on EFI_STUB diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile index a2d0009560d0..4770c7c4e3c7 100644 --- a/drivers/firmware/efi/Makefile +++ b/drivers/firmware/efi/Makefile @@ -29,6 +29,7 @@ obj-$(CONFIG_APPLE_PROPERTIES) +=3D apple-properties.o obj-$(CONFIG_EFI_RCI2_TABLE) +=3D rci2-table.o obj-$(CONFIG_EFI_EMBEDDED_FIRMWARE) +=3D embedded-firmware.o obj-$(CONFIG_LOAD_UEFI_KEYS) +=3D mokvar-table.o +obj-$(CONFIG_OVMF_DEBUG_LOG) +=3D ovmf-log.o =20 obj-$(CONFIG_SYSFB) +=3D sysfb_efi.o =20 --=20 2.50.0