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() and __die_body() so that a future
commit can print extra information after the header line.

 [ bp: Comment the KASAN-specific usage of gp_addr. ]

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: kasan-dev@googlegroups.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191218231150.12139-3-jannh@google.com

diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index 75f1e35..247ab14 100644 (file)
--- 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 e07424e..8995bf1 100644 (file)
--- 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 108ab1e..2afd7d8 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -619,7 +619,14 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
                                 "maybe for address",
                                 gp_addr);
 
-               die(desc, regs, error_code);
+               /*
+                * KASAN is interested only in the non-canonical case, clear it
+                * otherwise.
+                */
+               if (hint != GP_NON_CANONICAL)
+                       gp_addr = 0;
+
+               die_addr(desc, regs, error_code, gp_addr);
                return;
        }