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From:   Omar Sandoval <osandov@osandov.com>
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] x86: define arch_crash_save_vmcoreinfo() if CONFIG_CRASH_CORE=y
Date:   Mon,  2 Dec 2019 10:02:29 -0800
Message-Id: <9e9eb78c157d26d80f8781f8ce0e088fd12120b4.1575309711.git.osandov@fb.com>
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Sender: linux-kernel-owner@vger.kernel.org
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From: Omar Sandoval <osandov@fb.com>

kernel/crash_core.c calls arch_crash_save_vmcoreinfo() to get
arch-specific bits for vmcoreinfo. If it is not defined, then it has a
no-op fallback. kernel/crash_core.c is gated behind CONFIG_CRASH_CORE.
However, x86 defines arch_crash_save_vmcoreinfo() in
arch/x86/kernel/machine_kexec_*.c, which is gated behind
CONFIG_KEXEC_CORE. So, a kernel with CONFIG_CRASH_CORE=y and
CONFIG_KEXEC_CORE=n uses the fallback and gets incomplete vmcoreinfo
data, which can confuse applications reading vmcoreinfo from
/proc/kcore.

Fix it by moving arch_crash_save_vmcoreinfo() into two new
arch/x86/kernel/crash_core_*.c files, which are gated behind
CONFIG_CRASH_CORE.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
Based on Linus's tree.

 arch/x86/kernel/Makefile           |  1 +
 arch/x86/kernel/crash_core_32.c    | 17 +++++++++++++++++
 arch/x86/kernel/crash_core_64.c    | 24 ++++++++++++++++++++++++
 arch/x86/kernel/machine_kexec_32.c | 12 ------------
 arch/x86/kernel/machine_kexec_64.c | 19 -------------------
 5 files changed, 42 insertions(+), 31 deletions(-)
 create mode 100644 arch/x86/kernel/crash_core_32.c
 create mode 100644 arch/x86/kernel/crash_core_64.c

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 6175e370ee4a..9b294c13809a 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -94,6 +94,7 @@ obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace_$(BITS).o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
 obj-$(CONFIG_FTRACE_SYSCALLS)	+= ftrace.o
 obj-$(CONFIG_X86_TSC)		+= trace_clock.o
+obj-$(CONFIG_CRASH_CORE)	+= crash_core_$(BITS).o
 obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec_$(BITS).o
 obj-$(CONFIG_KEXEC_CORE)	+= relocate_kernel_$(BITS).o crash.o
 obj-$(CONFIG_KEXEC_FILE)	+= kexec-bzimage64.o
diff --git a/arch/x86/kernel/crash_core_32.c b/arch/x86/kernel/crash_core_32.c
new file mode 100644
index 000000000000..c0159a7bca6d
--- /dev/null
+++ b/arch/x86/kernel/crash_core_32.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/crash_core.h>
+
+#include <asm/pgtable.h>
+#include <asm/setup.h>
+
+void arch_crash_save_vmcoreinfo(void)
+{
+#ifdef CONFIG_NUMA
+	VMCOREINFO_SYMBOL(node_data);
+	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
+#endif
+#ifdef CONFIG_X86_PAE
+	VMCOREINFO_CONFIG(X86_PAE);
+#endif
+}
diff --git a/arch/x86/kernel/crash_core_64.c b/arch/x86/kernel/crash_core_64.c
new file mode 100644
index 000000000000..845a57eb4eb7
--- /dev/null
+++ b/arch/x86/kernel/crash_core_64.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/crash_core.h>
+
+#include <asm/pgtable.h>
+#include <asm/setup.h>
+
+void arch_crash_save_vmcoreinfo(void)
+{
+	u64 sme_mask = sme_me_mask;
+
+	VMCOREINFO_NUMBER(phys_base);
+	VMCOREINFO_SYMBOL(init_top_pgt);
+	vmcoreinfo_append_str("NUMBER(pgtable_l5_enabled)=%d\n",
+			      pgtable_l5_enabled());
+
+#ifdef CONFIG_NUMA
+	VMCOREINFO_SYMBOL(node_data);
+	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
+#endif
+	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
+	VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
+	VMCOREINFO_NUMBER(sme_mask);
+}
diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index 7b45e8daad22..02bddfc122a4 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -250,15 +250,3 @@ void machine_kexec(struct kimage *image)
 
 	__ftrace_enabled_restore(save_ftrace_enabled);
 }
-
-void arch_crash_save_vmcoreinfo(void)
-{
-#ifdef CONFIG_NUMA
-	VMCOREINFO_SYMBOL(node_data);
-	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
-#endif
-#ifdef CONFIG_X86_PAE
-	VMCOREINFO_CONFIG(X86_PAE);
-#endif
-}
-
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 16e125a50b33..ad5cdd6a5f23 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -398,25 +398,6 @@ void machine_kexec(struct kimage *image)
 	__ftrace_enabled_restore(save_ftrace_enabled);
 }
 
-void arch_crash_save_vmcoreinfo(void)
-{
-	u64 sme_mask = sme_me_mask;
-
-	VMCOREINFO_NUMBER(phys_base);
-	VMCOREINFO_SYMBOL(init_top_pgt);
-	vmcoreinfo_append_str("NUMBER(pgtable_l5_enabled)=%d\n",
-			pgtable_l5_enabled());
-
-#ifdef CONFIG_NUMA
-	VMCOREINFO_SYMBOL(node_data);
-	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
-#endif
-	vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
-			      kaslr_offset());
-	VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
-	VMCOREINFO_NUMBER(sme_mask);
-}
-
 /* arch-dependent functionality related to kexec file-based syscall */
 
 #ifdef CONFIG_KEXEC_FILE
-- 
2.24.0