linux-kernel - [PATCH v7 3/4] x86/dumpstack: Introduce die_addr() for die() with #GP fault address

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Date:   Thu, 19 Dec 2019 00:11:49 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        jannh@...gle.com
Cc:     linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH v7 3/4] x86/dumpstack: Introduce die_addr() for die() with #GP
 fault address

Split __die() into __die_header() and __die_body(). This allows inserting
extra information below the header line that initiates the bug report.

Introduce a new function die_addr() that behaves like die(), but is for
faults only and uses __die_header()+__die_body() so that a future commit
can print extra information after the header line.

Signed-off-by: Jann Horn <jannh@...gle.com>
---

Notes:
    v3:
      new patch
    v4-v6:
      no changes
    v7:
     - introduce die_addr() instead of open-coding __die_header()
       and __die_body() calls in traps.c (Borislav)
     - make __die_header() and __die_body() static
     - rewrite commit message

 arch/x86/include/asm/kdebug.h |  1 +
 arch/x86/kernel/dumpstack.c   | 24 +++++++++++++++++++++++-
 arch/x86/kernel/traps.c       |  5 ++++-
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index 75f1e35e7c15..247ab14c6309 100644
--- a/arch/x86/include/asm/kdebug.h
+++ b/arch/x86/include/asm/kdebug.h
@@ -33,6 +33,7 @@ enum show_regs_mode {
 };
 
 extern void die(const char *, struct pt_regs *,long);
+void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr);
 extern int __must_check __die(const char *, struct pt_regs *, long);
 extern void show_stack_regs(struct pt_regs *regs);
 extern void __show_regs(struct pt_regs *regs, enum show_regs_mode);
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index e07424e19274..8995bf10c97c 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -365,7 +365,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 }
 NOKPROBE_SYMBOL(oops_end);
 
-int __die(const char *str, struct pt_regs *regs, long err)
+static void __die_header(const char *str, struct pt_regs *regs, long err)
 {
 	const char *pr = "";
 
@@ -384,7 +384,11 @@ int __die(const char *str, struct pt_regs *regs, long err)
 	       IS_ENABLED(CONFIG_KASAN)   ? " KASAN"           : "",
 	       IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ?
 	       (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");
+}
+NOKPROBE_SYMBOL(__die_header);
 
+static int __die_body(const char *str, struct pt_regs *regs, long err)
+{
 	show_regs(regs);
 	print_modules();
 
@@ -394,6 +398,13 @@ int __die(const char *str, struct pt_regs *regs, long err)
 
 	return 0;
 }
+NOKPROBE_SYMBOL(__die_body);
+
+int __die(const char *str, struct pt_regs *regs, long err)
+{
+	__die_header(str, regs, err);
+	return __die_body(str, regs, err);
+}
 NOKPROBE_SYMBOL(__die);
 
 /*
@@ -410,6 +421,17 @@ void die(const char *str, struct pt_regs *regs, long err)
 	oops_end(flags, regs, sig);
 }
 
+void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr)
+{
+	unsigned long flags = oops_begin();
+	int sig = SIGSEGV;
+
+	__die_header(str, regs, err);
+	if (__die_body(str, regs, err))
+		sig = 0;
+	oops_end(flags, regs, sig);
+}
+
 void show_regs(struct pt_regs *regs)
 {
 	show_regs_print_info(KERN_DEFAULT);
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c8b4ae6aed5b..4c691bb9e0d9 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -621,7 +621,10 @@ do_general_protection(struct pt_regs *regs, long error_code)
 				 "maybe for address",
 				 gp_addr);
 
-		die(desc, regs, error_code);
+		if (hint != GP_NON_CANONICAL)
+			gp_addr = 0;
+
+		die_addr(desc, regs, error_code, gp_addr);
 		return;
 	}
 
-- 
2.24.1.735.g03f4e72817-goog