[MODERATED] [PATCH v5 05/11] [PATCH v5 05/10] Linux Patch #5

[konrad.wilk@oracle.com]

It does not do much except show the words 'Vulnerable' for recent x86
cores. Intel cores prior to Nehalem are known not to be vulnerable, and
so are some Atoms and some Xeon Phi.

It assumes that older Cyrix, Centaur, etc. cores are immune.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
v1.3: Remove AMD
    s/md/mdd/
v1.4: s/mdd/sbb/
v3: s/SSB/SPEC_STORE_BYPASS
  Rework the logic in cpu_set_bug_bits to be inverse.
v4: Expanded the not affected array
  - s/X86_BUG_CPU_SPEC_STORE_BYPASS/X86_BUG_SPEC_STORE_BYPASS/
---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/kernel/cpu/bugs.c         |  5 +++++
 arch/x86/kernel/cpu/common.c       | 20 ++++++++++++++++++++
 drivers/base/cpu.c                 |  8 ++++++++
 include/linux/cpu.h                |  2 ++
 5 files changed, 36 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index d554c11e01ff..c70b9a5d5045 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -362,5 +362,6 @@
 #define X86_BUG_CPU_MELTDOWN		X86_BUG(14) /* CPU is affected by meltdown attack and needs kernel page table isolation */
 #define X86_BUG_SPECTRE_V1		X86_BUG(15) /* CPU is affected by Spectre variant 1 attack with conditional branches */
 #define X86_BUG_SPECTRE_V2		X86_BUG(16) /* CPU is affected by Spectre variant 2 attack with indirect branches */
+#define X86_BUG_SPEC_STORE_BYPASS	X86_BUG(17) /* CPU is affected by speculative store bypass attack */
 
 #endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index af30bf6a2007..004b42f71c45 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -404,4 +404,9 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, c
 {
 	return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
 }
+
+ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
+}
 #endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 74722c38a836..7ae1f2e6caf7 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -918,10 +918,30 @@ static const __initconst struct x86_cpu_id cpu_no_meltdown[] = {
 	{}
 };
 
+static const __initconst struct x86_cpu_id cpu_no_spec_store_bypass[] = {
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_PINEVIEW },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_LINCROFT },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_PENWELL },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_CLOVERVIEW },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_CEDARVIEW },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_SILVERMONT1 },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_AIRMONT },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_XEON_PHI_KNL },
+	{ X86_VENDOR_INTEL,     6, INTEL_FAM6_XEON_PHI_KNM },
+	{ X86_VENDOR_CENTAUR,	5 },
+	{ X86_VENDOR_INTEL,	5 },
+	{ X86_VENDOR_NSC,	5 },
+	{ X86_VENDOR_ANY,	4 },
+	{}
+};
+
 static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
 {
 	u64 ia32_cap = 0;
 
+	if (!x86_match_cpu(cpu_no_spec_store_bypass))
+		setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);
+
 	if (x86_match_cpu(cpu_no_speculation))
 		return;
 
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index d21a2d913107..827905794b48 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -532,14 +532,22 @@ ssize_t __weak cpu_show_spectre_v2(struct device *dev,
 	return sprintf(buf, "Not affected\n");
 }
 
+ssize_t __weak cpu_show_spec_store_bypass(struct device *dev,
+					  struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
 static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
+static DEVICE_ATTR(spec_store_bypass, 0444, cpu_show_spec_store_bypass, NULL);
 
 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 	&dev_attr_meltdown.attr,
 	&dev_attr_spectre_v1.attr,
 	&dev_attr_spectre_v2.attr,
+	&dev_attr_spec_store_bypass.attr,
 	NULL
 };
 
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 7b01bc11c692..a97a63eef59f 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -53,6 +53,8 @@ extern ssize_t cpu_show_spectre_v1(struct device *dev,
 				   struct device_attribute *attr, char *buf);
 extern ssize_t cpu_show_spectre_v2(struct device *dev,
 				   struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_spec_store_bypass(struct device *dev,
+					  struct device_attribute *attr, char *buf);
 
 extern __printf(4, 5)
 struct device *cpu_device_create(struct device *parent, void *drvdata,
-- 
2.14.3