git: 61a7ad35bb20 - stable/13 - Teach DTrace about BTI on arm64

The branch stable/13 has been updated by andrew:

URL: https://cgit.FreeBSD.org/src/commit/?id=61a7ad35bb20b00755515e484583b92b07c1923d

commit 61a7ad35bb20b00755515e484583b92b07c1923d
Author:     Andrew Turner <andrew@FreeBSD.org>
AuthorDate: 2021-12-22 17:26:33 +0000
Commit:     Andrew Turner <andrew@FreeBSD.org>
CommitDate: 2022-02-22 16:23:07 +0000

    Teach DTrace about BTI on arm64
    
    The Branch Target Identification (BTI) Armv8-A extension adds new
    instructions that can be placed where we may indirrectly branch to,
    e.g. at the start of a function called via a function pointer. We can't
    emulate these in DTrace as the kernel will have raised a different
    exception before the DTrace handler has run.
    
    Skip over the BTI instruction if it's used as the first instruction in
    a function.
    
    Sponsored by:   The FreeBSD Foundation
    
    (cherry picked from commit b5876847acfeae2dd3a655cde8cdf6145aed16d8)
---
 sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h | 3 +++
 sys/cddl/dev/fbt/aarch64/fbt_isa.c                   | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h b/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
index f15a971f12be..c15cc39189b1 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
+++ b/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
@@ -2466,6 +2466,9 @@ extern void dtrace_helpers_destroy(proc_t *);
 #define	B_DATA_MASK	0x00ffffff
 #define	B_INSTR		0x14000000
 
+#define	BTI_MASK	0xffffff3f
+#define	BTI_INSTR	0xd503241f
+
 #define	NOP_INSTR	0xd503201f
 
 #define	RET_INSTR	0xd65f03c0
diff --git a/sys/cddl/dev/fbt/aarch64/fbt_isa.c b/sys/cddl/dev/fbt/aarch64/fbt_isa.c
index d00aabf0cc81..07f02e2edb72 100644
--- a/sys/cddl/dev/fbt/aarch64/fbt_isa.c
+++ b/sys/cddl/dev/fbt/aarch64/fbt_isa.c
@@ -118,6 +118,14 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
 	instr = (uint32_t *)(symval->value);
 	limit = (uint32_t *)(symval->value + symval->size);
 
+	/*
+	 * Ignore any bti instruction at the start of the function
+	 * we need to keep it there for any indirect branches calling
+	 * the function on Armv8.5+
+	 */
+	if ((*instr & BTI_MASK) == BTI_INSTR)
+		instr++;
+
 	/* Look for stp (pre-indexed) operation */
 	found = false;
 	/*