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From: Borislav Petkov <bp@alien8.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@amacapital.net>, X86 ML <x86@kernel.org>
Subject: [PATCH -v2 3/3] x86/dumpstack: Add show_stack_regs() and use it
Date: Tue,  5 Jul 2016 00:31:27 +0200
Message-ID: <1467671487-10344-4-git-send-email-bp@alien8.de> (raw)
In-Reply-To: <1467671487-10344-1-git-send-email-bp@alien8.de>

From: Borislav Petkov <bp@suse.de>

Add a helper to dump supplied pt_regs and use it in the MSR exception
handling code to have precise stack traces pointing to the actual
function causing the MSR access exception and not the stack frame of the
exception handler itself.

The new output looks like this:

 unchecked MSR access error: RDMSR from 0xdeadbeef at rIP: 0xffffffff8102ddb6 (early_init_intel+0x16/0x3a0)
  00000000756e6547 ffffffff81c03f68 ffffffff81dd0940 ffffffff81c03f10
  ffffffff81d42e65 0000000001000000 ffffffff81c03f58 ffffffff81d3e5a3
  0000800000000000 ffffffff81800080 ffffffffffffffff 0000000000000000
 Call Trace:
  [<ffffffff81d42e65>] early_cpu_init+0xe7/0x136
  [<ffffffff81d3e5a3>] setup_arch+0xa5/0x9df
  [<ffffffff81d38bb9>] start_kernel+0x9f/0x43a
  [<ffffffff81d38294>] x86_64_start_reservations+0x2f/0x31
  [<ffffffff81d383fe>] x86_64_start_kernel+0x168/0x176

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/kdebug.h |  1 +
 arch/x86/kernel/dumpstack.c   |  5 +++++
 arch/x86/mm/extable.c         | 13 ++++++++-----
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index e5f5dc9787d5..1ef9d581b5d9 100644
--- a/arch/x86/include/asm/kdebug.h
+++ b/arch/x86/include/asm/kdebug.h
@@ -26,6 +26,7 @@ extern void die(const char *, struct pt_regs *,long);
 extern int __must_check __die(const char *, struct pt_regs *, long);
 extern void show_trace(struct task_struct *t, struct pt_regs *regs,
 		       unsigned long *sp, unsigned long bp);
+extern void show_stack_regs(struct pt_regs *regs);
 extern void __show_regs(struct pt_regs *regs, int all);
 extern unsigned long oops_begin(void);
 extern void oops_end(unsigned long, struct pt_regs *, int signr);
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index ef8017ca5ba9..d66e5ac823b2 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -197,6 +197,11 @@ void show_stack(struct task_struct *task, unsigned long *sp)
 	show_stack_log_lvl(task, NULL, sp, bp, "");
 }
 
+void show_stack_regs(struct pt_regs *regs)
+{
+	show_stack_log_lvl(current, regs, (unsigned long *)regs->sp, regs->bp, "");
+}
+
 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
 static int die_owner = -1;
 static unsigned int die_nest_count;
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 4bb53b89f3c5..fafc771568c7 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -1,6 +1,7 @@
 #include <linux/module.h>
 #include <asm/uaccess.h>
 #include <asm/traps.h>
+#include <asm/kdebug.h>
 
 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
 			    struct pt_regs *, int);
@@ -46,8 +47,9 @@ EXPORT_SYMBOL(ex_handler_ext);
 bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
 			     struct pt_regs *regs, int trapnr)
 {
-	WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x\n",
-		  (unsigned int)regs->cx);
+	if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pF)\n",
+			 (unsigned int)regs->cx, regs->ip, (void *)regs->ip))
+		show_stack_regs(regs);
 
 	/* Pretend that the read succeeded and returned 0. */
 	regs->ip = ex_fixup_addr(fixup);
@@ -60,9 +62,10 @@ EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
 bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
 			     struct pt_regs *regs, int trapnr)
 {
-	WARN_ONCE(1, "unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x)\n",
-		  (unsigned int)regs->cx,
-		  (unsigned int)regs->dx, (unsigned int)regs->ax);
+	if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pF)\n",
+			 (unsigned int)regs->cx, (unsigned int)regs->dx,
+			 (unsigned int)regs->ax,  regs->ip, (void *)regs->ip))
+		show_stack_regs(regs);
 
 	/* Pretend that the write succeeded. */
 	regs->ip = ex_fixup_addr(fixup);
-- 
2.7.3

  parent reply index

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-04 22:31 [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Borislav Petkov
2016-07-04 22:31 ` [PATCH -v2 1/3] x86/dumpstack: Honor supplied @regs arg Borislav Petkov
2016-07-04 22:31 ` [PATCH -v2 2/3] printk: Make the printk*once() variants return a value Borislav Petkov
2016-07-08 12:08   ` [tip:x86/debug] " tip-bot for Borislav Petkov
2016-07-09  2:40     ` Joe Perches
2016-07-09  7:50       ` Borislav Petkov
2016-07-09 17:56         ` Joe Perches
2016-07-10  6:49           ` Borislav Petkov
2016-07-10  8:23             ` Joe Perches
2016-07-10 12:06               ` Borislav Petkov
2016-07-10 12:33                 ` Joe Perches
2016-07-04 22:31 ` Borislav Petkov [this message]
2016-07-08 12:08   ` [tip:x86/debug] x86/dumpstack: Add show_stack_regs() and use it tip-bot for Borislav Petkov
2016-07-06 12:58 ` [PATCH -v2 0/3] x86/MSR: Improve unhandled MSR access error message Andy Lutomirski
2016-07-06 13:11   ` Borislav Petkov
  -- strict thread matches above, loose matches on Subject: below --
2016-06-16  0:28 [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski
2016-06-16  0:28 ` [PATCH 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski
2016-06-16  0:28 ` [PATCH 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski
2016-06-16  0:28 ` [PATCH 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski
2016-06-16  0:28 ` [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks Andy Lutomirski
2016-06-16 11:10   ` Vladimir Davydov
2016-06-16 17:21     ` Andy Lutomirski
2016-06-16 19:20       ` Andy Lutomirski
2016-06-16 15:33   ` Josh Poimboeuf
2016-06-16 17:39     ` Andy Lutomirski
2016-06-16 19:39       ` Josh Poimboeuf
2016-06-16  0:28 ` [PATCH 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski
2016-06-16  0:28 ` [PATCH 06/13] fork: Add generic vmalloced stack support Andy Lutomirski
2016-06-16 17:25   ` Kees Cook
2016-06-16 17:37     ` Andy Lutomirski
2016-06-16  0:28 ` [PATCH 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski
2016-06-16  0:28 ` [PATCH 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski
2016-06-16 17:50   ` Josh Poimboeuf
2016-06-16 17:57     ` Andy Lutomirski
2016-06-16  0:28 ` [PATCH 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski
2016-06-16 11:56   ` Borislav Petkov
2016-07-08 12:07   ` [tip:x86/debug] x86/dumpstack: Honor supplied @regs arg tip-bot for Andy Lutomirski
2016-06-16  0:28 ` [PATCH 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski
2016-06-16 18:16   ` Josh Poimboeuf
2016-06-16 18:22     ` Andy Lutomirski
2016-06-16 18:33       ` Josh Poimboeuf
2016-06-16 18:37         ` Andy Lutomirski
2016-06-16 18:54           ` Josh Poimboeuf
2016-06-16  0:28 ` [PATCH 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski
2016-06-16  0:28 ` [PATCH 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski
2016-06-16  4:17   ` Mika Penttilä
2016-06-16  5:33     ` Andy Lutomirski
2016-06-16 13:11       ` [kernel-hardening] " Rik van Riel
2016-06-16  0:28 ` [PATCH 13/13] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski
2016-06-16  6:05 ` [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core) Heiko Carstens
2016-06-16 17:50   ` Andy Lutomirski
2016-06-16 18:14     ` Andy Lutomirski
2016-06-16 21:27       ` Andy Lutomirski
2016-06-17  3:58   ` Andy Lutomirski
2016-06-17  7:27     ` Heiko Carstens
2016-06-17 17:38       ` Andy Lutomirski
2016-06-20  5:58         ` Heiko Carstens
2016-06-20  6:01           ` Andy Lutomirski
2016-06-20  7:07             ` Heiko Carstens
2016-06-16 17:24 ` Kees Cook

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