linux-kernel - [PATCH for 2.6.22] [4/10] x86: Disable DAC on VIA bridges

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20070620102332.C160F14AEF@wotan.suse.de>
Date:	Wed, 20 Jun 2007 12:23:32 +0200 (CEST)
From:	Andi Kleen <ak@...e.de>
To:	torvalds@...l.org, linux-kernel@...r.kernel.org, patches@...-64.org
Subject: [PATCH for 2.6.22] [4/10] x86: Disable DAC on VIA bridges


Several reports that VIA bridges don't support DAC and corrupt
data.  I don't know if it's fixed, but let's just blacklist
them all for now.

It can be overwritten with iommu=usedac

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/i386/kernel/pci-dma.c     |   27 +++++++++++++++++++++++++++
 arch/x86_64/kernel/pci-dma.c   |   12 ++++++++++++
 include/asm-i386/dma-mapping.h |    6 ++++++
 3 files changed, 45 insertions(+)

Index: linux/arch/x86_64/kernel/pci-dma.c
===================================================================
--- linux.orig/arch/x86_64/kernel/pci-dma.c
+++ linux/arch/x86_64/kernel/pci-dma.c
@@ -322,5 +322,17 @@ static int __init pci_iommu_init(void)
 	return 0;
 }
 
+#ifdef CONFIG_PCI
+/* Many VIA bridges seem to corrupt data for DAC. Disable it here */
+
+static __devinit void via_no_dac(struct pci_dev *dev)
+{
+	if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI && forbid_dac == 0) {
+		printk(KERN_INFO "PCI: VIA PCI bridge detected. Disabling DAC.\n");
+		forbid_dac = 1;
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID, via_no_dac);
+#endif
 /* Must execute after PCI subsystem */
 fs_initcall(pci_iommu_init);
Index: linux/arch/i386/kernel/pci-dma.c
===================================================================
--- linux.orig/arch/i386/kernel/pci-dma.c
+++ linux/arch/i386/kernel/pci-dma.c
@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/pci.h>
 #include <linux/module.h>
+#include <linux/pci.h>
 #include <asm/io.h>
 
 struct dma_coherent_mem {
@@ -148,3 +149,29 @@ void *dma_mark_declared_memory_occupied(
 	return mem->virt_base + (pos << PAGE_SHIFT);
 }
 EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
+
+#ifdef CONFIG_PCI
+/* Many VIA bridges seem to corrupt data for DAC. Disable it here */
+
+int forbid_dac;
+EXPORT_SYMBOL(forbid_dac);
+
+static __devinit void via_no_dac(struct pci_dev *dev)
+{
+	if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI && forbid_dac == 0) {
+		printk(KERN_INFO "PCI: VIA PCI bridge detected. Disabling DAC.\n");
+		forbid_dac = 1;
+	}
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID, via_no_dac);
+
+static int check_iommu(char *s)
+{
+	if (!strcmp(s, "usedac")) {
+		forbid_dac = -1;
+		return 1;
+	}
+	return 0;
+}
+__setup("iommu=", check_iommu);
+#endif
Index: linux/include/asm-i386/dma-mapping.h
===================================================================
--- linux.orig/include/asm-i386/dma-mapping.h
+++ linux/include/asm-i386/dma-mapping.h
@@ -123,6 +123,8 @@ dma_mapping_error(dma_addr_t dma_addr)
 	return 0;
 }
 
+extern int forbid_dac;
+
 static inline int
 dma_supported(struct device *dev, u64 mask)
 {
@@ -134,6 +136,10 @@ dma_supported(struct device *dev, u64 ma
         if(mask < 0x00ffffff)
                 return 0;
 
+	/* Work around chipset bugs */
+	if (forbid_dac > 0 && mask > 0xffffffffULL)
+		return 0;
+
 	return 1;
 }
 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/