linux-kernel - [PATCH V10 22/44] x86/fault: Print PKS MSR on fault

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Date:   Tue, 19 Apr 2022 10:06:27 -0700
From:   ira.weiny@...el.com
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V10 22/44] x86/fault: Print PKS MSR on fault

From: Ira Weiny <ira.weiny@...el.com>

If a PKS fault occurs it will be easier to debug if the PKS MSR value at
the time of the fault is known.

Add pks_show_regs() to __show_regs() to show the PKRS MSR on fault if
enabled.

An 'executive summary' of the pt_regs are saved in __die_header() which
ensures that the first registers are saved in the event of multiple
faults.  Teach this code about the extended pt_registers such that the
PKS code can get to the original pkrs value as well.

Suggested-by: Andy Lutomirski <luto@...nel.org>
Suggested-by: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes for V9
	From Dave Hansen
		Move this output to __show_regs() next to the PKRU
			register dump

Changes for V8
	Split this into it's own patch.
---
 arch/x86/include/asm/pks.h   |  3 +++
 arch/x86/kernel/dumpstack.c  | 32 ++++++++++++++++++++++++++++++--
 arch/x86/kernel/process_64.c |  1 +
 arch/x86/mm/pkeys.c          | 11 +++++++++++
 4 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pks.h b/arch/x86/include/asm/pks.h
index b69e03a141fe..de67d5b5a2af 100644
--- a/arch/x86/include/asm/pks.h
+++ b/arch/x86/include/asm/pks.h
@@ -8,6 +8,7 @@ void pks_setup(void);
 void x86_pkrs_load(struct thread_struct *thread);
 void pks_save_pt_regs(struct pt_regs *regs);
 void pks_restore_pt_regs(struct pt_regs *regs);
+void pks_show_regs(struct pt_regs *regs, const char *log_lvl);
 
 bool pks_handle_key_fault(struct pt_regs *regs, unsigned long hw_error_code,
 			  unsigned long address);
@@ -18,6 +19,8 @@ static inline void pks_setup(void) { }
 static inline void x86_pkrs_load(struct thread_struct *thread) { }
 static inline void pks_save_pt_regs(struct pt_regs *regs) { }
 static inline void pks_restore_pt_regs(struct pt_regs *regs) { }
+static inline void pks_show_regs(struct pt_regs *regs,
+				 const char *log_lvl) { }
 
 static inline bool pks_handle_key_fault(struct pt_regs *regs,
 					unsigned long hw_error_code,
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index afae4dd77495..5fae75113def 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -27,8 +27,36 @@ int panic_on_unrecovered_nmi;
 int panic_on_io_nmi;
 static int die_counter;
 
+#ifdef CONFIG_ARCH_HAS_PTREGS_AUXILIARY
+
+static struct pt_regs_extended exec_summary_regs;
+
+static void save_exec_summary(struct pt_regs *regs)
+{
+	exec_summary_regs = *(to_extended_pt_regs(regs));
+}
+
+static struct pt_regs *retrieve_exec_summary(void)
+{
+	return &exec_summary_regs.pt_regs;
+}
+
+#else /* !CONFIG_ARCH_HAS_PTREGS_AUXILIARY */
+
 static struct pt_regs exec_summary_regs;
 
+static void save_exec_summary(struct pt_regs *regs)
+{
+	exec_summary_regs = *regs;
+}
+
+static struct pt_regs *retrieve_exec_summary(void)
+{
+	return &exec_summary_regs;
+}
+
+#endif /* CONFIG_ARCH_HAS_PTREGS_AUXILIARY */
+
 bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
 			   struct stack_info *info)
 {
@@ -363,7 +391,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 	oops_exit();
 
 	/* Executive summary in case the oops scrolled away */
-	__show_regs(&exec_summary_regs, SHOW_REGS_ALL, KERN_DEFAULT);
+	__show_regs(retrieve_exec_summary(), SHOW_REGS_ALL, KERN_DEFAULT);
 
 	if (!signr)
 		return;
@@ -390,7 +418,7 @@ static void __die_header(const char *str, struct pt_regs *regs, long err)
 
 	/* Save the regs of the first oops for the executive summary later. */
 	if (!die_counter)
-		exec_summary_regs = *regs;
+		save_exec_summary(regs);
 
 	if (IS_ENABLED(CONFIG_PREEMPTION))
 		pr = IS_ENABLED(CONFIG_PREEMPT_RT) ? " PREEMPT_RT" : " PREEMPT";
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 5cfa1f8c8465..cd8f362a83c4 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -140,6 +140,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
 
 	if (cpu_feature_enabled(X86_FEATURE_OSPKE))
 		printk("%sPKRU: %08x\n", log_lvl, read_pkru());
+	pks_show_regs(regs, log_lvl);
 }
 
 void release_thread(struct task_struct *dead_task)
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index dd02e76d0359..a993c9b23815 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -374,6 +374,17 @@ void pks_restore_pt_regs(struct pt_regs *regs)
 	pks_write_pkrs(current->thread.pkrs);
 }
 
+void pks_show_regs(struct pt_regs *regs, const char *log_lvl)
+{
+	struct pt_regs_auxiliary *aux_pt_regs;
+
+	if (!cpu_feature_enabled(X86_FEATURE_PKS))
+		return;
+
+	aux_pt_regs = &to_extended_pt_regs(regs)->aux;
+	printk("%sPKRS: 0x%x\n", log_lvl, aux_pt_regs->pkrs);
+}
+
 /*
  * PKS is independent of PKU and either or both may be supported on a CPU.
  *
-- 
2.35.1