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

ira.weiny
2022-01-27T17:56:31Z

From: Ira Weiny <ira.weiny@intel.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@kernel.org>
Signed-off-by: Ira Weiny <ira.weiny@intel.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