linux-kernel - [patch V3 06/23] bug: Annotate WARN/BUG/stackfail as noinstr safe

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Message-Id: <20200320180032.994128577@linutronix.de>
Date:   Fri, 20 Mar 2020 19:00:02 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Paul McKenney <paulmck@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: [patch V3 06/23] bug: Annotate WARN/BUG/stackfail as noinstr safe

Warnings, bugs and stack protection fails from noinstr sections, e.g. low
level and early entry code, are likely to be fatal.

Mark them as "safe" to be invoked from noinstr protected code to avoid
annotating all usage sites. Getting the information out is important.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/include/asm/bug.h |    3 +++
 include/asm-generic/bug.h  |    9 +++++++--
 kernel/panic.c             |    4 +++-
 3 files changed, 13 insertions(+), 3 deletions(-)

--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -70,13 +70,16 @@ do {									\
 #define HAVE_ARCH_BUG
 #define BUG()							\
 do {								\
+	instr_begin();						\
 	_BUG_FLAGS(ASM_UD2, 0);					\
 	unreachable();						\
 } while (0)
 
 #define __WARN_FLAGS(flags)					\
 do {								\
+	instr_begin();						\
 	_BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags));		\
+	instr_end();						\
 	annotate_reachable();					\
 } while (0)
 
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -83,14 +83,19 @@ extern __printf(4, 5)
 void warn_slowpath_fmt(const char *file, const int line, unsigned taint,
 		       const char *fmt, ...);
 #define __WARN()		__WARN_printf(TAINT_WARN, NULL)
-#define __WARN_printf(taint, arg...)					\
-	warn_slowpath_fmt(__FILE__, __LINE__, taint, arg)
+#define __WARN_printf(taint, arg...) do {				\
+	instr_begin();							\
+	warn_slowpath_fmt(__FILE__, __LINE__, taint, arg);		\
+	instr_end();							\
+	while (0)
 #else
 extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
 #define __WARN()		__WARN_FLAGS(BUGFLAG_TAINT(TAINT_WARN))
 #define __WARN_printf(taint, arg...) do {				\
+		instr_begin();						\
 		__warn_printk(arg);					\
 		__WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
+		instr_end();						\
 	} while (0)
 #define WARN_ON_ONCE(condition) ({				\
 	int __ret_warn_on = !!(condition);			\
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -662,10 +662,12 @@ device_initcall(register_warn_debugfs);
  * Called when gcc's -fstack-protector feature is used, and
  * gcc detects corruption of the on-stack canary value
  */
-__visible void __stack_chk_fail(void)
+__visible noinstr void __stack_chk_fail(void)
 {
+	instr_begin();
 	panic("stack-protector: Kernel stack is corrupted in: %pB",
 		__builtin_return_address(0));
+	instr_end();
 }
 EXPORT_SYMBOL(__stack_chk_fail);