2023-10-16 13:29:21

by Michael Roth

Subject: [PATCH v10 09/50] x86/traps: Define RMP violation #PF error code

From: Brijesh Singh <[email protected]>

Bit 31 in the page fault-error bit will be set when processor encounters
an RMP violation.

While at it, use the BIT() macro.

Signed-off-by: Brijesh Singh <[email protected]>
Signed-off by: Ashish Kalra <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Signed-off-by: Michael Roth <[email protected]>
---
arch/x86/include/asm/trap_pf.h | 4 ++++
arch/x86/mm/fault.c | 1 +
2 files changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/trap_pf.h b/arch/x86/include/asm/trap_pf.h
index afa524325e55..136707d7a961 100644
--- a/arch/x86/include/asm/trap_pf.h
+++ b/arch/x86/include/asm/trap_pf.h
@@ -2,6 +2,8 @@
#ifndef _ASM_X86_TRAP_PF_H
#define _ASM_X86_TRAP_PF_H

+#include <linux/bits.h> /* BIT() macro */
+
/*
* Page fault error code bits:
*
@@ -13,6 +15,7 @@
* bit 5 == 1: protection keys block access
* bit 6 == 1: shadow stack access fault
* bit 15 == 1: SGX MMU page-fault
+ * bit 31 == 1: fault was due to RMP violation
*/
enum x86_pf_error_code {
X86_PF_PROT = 1 << 0,
@@ -23,6 +26,7 @@ enum x86_pf_error_code {
X86_PF_PK = 1 << 5,
X86_PF_SHSTK = 1 << 6,
X86_PF_SGX = 1 << 15,
+ X86_PF_RMP = 1 << 31,
};

#endif /* _ASM_X86_TRAP_PF_H */
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ab778eac1952..7858b9515d4a 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -547,6 +547,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
!(error_code & X86_PF_PROT) ? "not-present page" :
(error_code & X86_PF_RSVD) ? "reserved bit violation" :
(error_code & X86_PF_PK) ? "protection keys violation" :
+ (error_code & X86_PF_RMP) ? "RMP violation" :
"permissions violation");

if (!(error_code & X86_PF_USER) && user_mode(regs)) {
--
2.25.1

2023-10-16 14:55:58

by Michael Roth

Subject: Re: [PATCH v10 09/50] x86/traps: Define RMP violation #PF error code

On Mon, Oct 16, 2023 at 07:14:07AM -0700, Dave Hansen wrote:
> On 10/16/23 06:27, Michael Roth wrote:
> > Bit 31 in the page fault-error bit will be set when processor encounters
> > an RMP violation. While at it, use the BIT() macro.
>
> Any idea where the BIT() use went? I remember seeing it in earlier
> versions.

Yah... this patch used to convert all the previous definitions over to
using BIT() as part of introducing the new RMP bit. I'm not sure what
happened, but a likely possibility is I hit a merge conflict at some
point due to upstream commit fd5439e0c9, which introduced this change:

X86_PF_SHSTK = 1 << 6,

and my brain probably defaulted to using the existing pattern to
resolve it. I'll get this fixed up.

-Mike