linux-kernel - [PATCH V8 26/44] x86/fault: Print PKS MSR on fault

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Message-Id: <20220127175505.851391-27-ira.weiny@intel.com>
Date:   Thu, 27 Jan 2022 09:54:47 -0800
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>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V8 26/44] 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 it if the PKS MSR value
at the time of the fault is known.

Add pks_dump_fault_info() to dump the PKRS MSR on fault if enabled.

Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes for V8
	Split this into it's own patch.
---
 arch/x86/include/asm/pks.h |  2 ++
 arch/x86/mm/fault.c        |  3 +++
 arch/x86/mm/pkeys.c        | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/pks.h b/arch/x86/include/asm/pks.h
index 82baa594cb3b..fc3c66f1bb04 100644
--- a/arch/x86/include/asm/pks.h
+++ b/arch/x86/include/asm/pks.h
@@ -8,6 +8,7 @@ void pks_setup(void);
 void pks_write_current(void);
 void pks_save_pt_regs(struct pt_regs *regs);
 void pks_restore_pt_regs(struct pt_regs *regs);
+void pks_dump_fault_info(struct pt_regs *regs);
 
 #else /* !CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS */
 
@@ -15,6 +16,7 @@ static inline void pks_setup(void) { }
 static inline void pks_write_current(void) { }
 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_dump_fault_info(struct pt_regs *regs) { }
 
 #endif /* CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS */
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 030eb3e08550..697c06f08103 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -549,6 +549,9 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
 		 (error_code & X86_PF_PK)    ? "protection keys violation" :
 					       "permissions violation");
 
+	if (error_code & X86_PF_PK)
+		pks_dump_fault_info(regs);
+
 	if (!(error_code & X86_PF_USER) && user_mode(regs)) {
 		struct desc_ptr idt, gdt;
 		u16 ldtr, tr;
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 33b7f84ed33b..bdd700d5ad03 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -288,6 +288,17 @@ void pks_restore_pt_regs(struct pt_regs *regs)
 	pks_write_pkrs(current->thread.pks_saved_pkrs);
 }
 
+void pks_dump_fault_info(struct pt_regs *regs)
+{
+	struct pt_regs_auxiliary *aux_pt_regs;
+
+	if (!cpu_feature_enabled(X86_FEATURE_PKS))
+		return;
+
+	aux_pt_regs = &to_extended_pt_regs(regs)->aux;
+	pr_alert("PKRS: 0x%x\n", aux_pt_regs->pks_thread_pkrs);
+}
+
 /*
  * PKS is independent of PKU and either or both may be supported on a CPU.
  *
-- 
2.31.1