git: 6f9e9eba984f - main - arm64: mte: handle synchronous tag check faults

The branch main has been updated by andrew:

URL: https://cgit.FreeBSD.org/src/commit/?id=6f9e9eba984f5c8d8a022c0ec99f844a911687fe

commit 6f9e9eba984f5c8d8a022c0ec99f844a911687fe
Author:     Harry Moulton <harry.moulton@arm.com>
AuthorDate: 2026-04-16 13:29:14 +0000
Commit:     Andrew Turner <andrew@FreeBSD.org>
CommitDate: 2026-04-16 14:22:24 +0000

    arm64: mte: handle synchronous tag check faults
    
    The Memory Tagging Extension supports both Synchronous and Asynchronous
    faults, called Tag Check Faults, which are configurable via
    SCTLR_EL1.TCF0 for userspace and SCTLR_EL1.TCF for the kernel.
    
    This commit adds support for handling synchronous tag check faults at
    EL0 and EL1, although these are only enabled on a per-process basis in
    userspace, kernel space does not enable tag check faults. A TCF in the
    kernel will cause a kernel panic like any other virtual memory fault,
    and a TCF in userspace will result in a SIGSEGV
    
    Reviewed by:    kib
    Sponsored by:   Arm Ltd
    Signed-off-by:  Harry Moulton <harry.moulton@arm.com>
    Differential Revision:  https://reviews.freebsd.org/D55947
---
 sys/arm64/arm64/trap.c | 22 ++++++++++++++++++++++
 sys/sys/signal.h       |  2 ++
 2 files changed, 24 insertions(+)

diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c
index ad461aa1bffc..1178817108e5 100644
--- a/sys/arm64/arm64/trap.c
+++ b/sys/arm64/arm64/trap.c
@@ -94,6 +94,7 @@ typedef void (abort_handler)(struct thread *, struct trapframe *, uint64_t,
 static abort_handler align_abort;
 static abort_handler data_abort;
 static abort_handler external_abort;
+static abort_handler tag_check_abort;
 
 static abort_handler *abort_handlers[] = {
 	[ISS_DATA_DFSC_TF_L0] = data_abort,
@@ -106,6 +107,7 @@ static abort_handler *abort_handlers[] = {
 	[ISS_DATA_DFSC_PF_L1] = data_abort,
 	[ISS_DATA_DFSC_PF_L2] = data_abort,
 	[ISS_DATA_DFSC_PF_L3] = data_abort,
+	[ISS_DATA_DFSC_TAG] = tag_check_abort,
 	[ISS_DATA_DFSC_ALIGN] = align_abort,
 	[ISS_DATA_DFSC_EXT] =  external_abort,
 	[ISS_DATA_DFSC_EXT_L0] =  external_abort,
@@ -250,6 +252,26 @@ external_abort(struct thread *td, struct trapframe *frame, uint64_t esr,
 	panic("Unhandled external data abort");
 }
 
+static void
+tag_check_abort(struct thread *td, struct trapframe *frame, uint64_t esr,
+    uint64_t far, int lower)
+{
+	/*
+	 * A Tag Check Fault should be handled as a SIGSEGV if it occurs
+	 * at EL0 and a kernel panic if at EL1.
+	 */
+	if (!lower) {
+		print_registers(frame);
+		print_gp_register("far", far);
+		printf(" esr: 0x%.16lx\n", esr);
+		panic("Tag Check Fault");
+	}
+
+	call_trapsignal(td, SIGSEGV, SEGV_MTESERR, (void *)far,
+	    ESR_ELx_EXCEPTION(frame->tf_esr));
+	userret(td, frame);
+}
+
 /*
  * It is unsafe to access the stack canary value stored in "td" until
  * kernel map translation faults are handled, see the pmap_klookup() call below.
diff --git a/sys/sys/signal.h b/sys/sys/signal.h
index c0b65c0c9ef0..863b981c2b7a 100644
--- a/sys/sys/signal.h
+++ b/sys/sys/signal.h
@@ -307,6 +307,8 @@ struct __siginfo32 {
 #define SEGV_ACCERR	2	/* Invalid permissions for mapped	*/
 				/* object.				*/
 #define	SEGV_PKUERR	100	/* x86: PKU violation			*/
+#define	SEGV_MTEAERR	100	/* arm64: Asynchronous Arm MTE error	*/
+#define	SEGV_MTESERR	101	/* arm64: Synchronous Arm MTE error	*/
 
 /* codes for SIGFPE */
 #define FPE_INTOVF	1	/* Integer overflow.			*/