bfd: aarch64: Fix stubs that may break BTI PR30076

Insert two stubs in a BTI enabled binary when fixing long calls: The
first is near the call site and uses an indirect jump like before,
but it targets the second stub that is near the call target site and
uses a direct jump.

This is needed when a single stub breaks BTI compatibility.

The stub layout is kept fixed between sizing and building the stubs,
so the location of the second stub is known at build time, this may
introduce padding between stubs when those are relaxed.  Stub layout
with BTI disabled is unchanged.

5 files changed, 192 insertions, 0 deletions

diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 48c8c12ef8f..80662de7e44 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -461,6 +461,9 @@ run_dump_test "bti-warn"
 run_dump_test "weak-tls"
 run_dump_test "undef-tls"
 
+run_dump_test "bti-far-1"
+run_dump_test "bti-far-2"
+
 if { ![skip_sframe_tests] } {
   run_dump_test "sframe-simple-1"
 }
diff --git a/ld/testsuite/ld-aarch64/bti-far-1.d b/ld/testsuite/ld-aarch64/bti-far-1.d
new file mode 100644
index 00000000000..d2dbc9db110
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-far-1.d
@@ -0,0 +1,83 @@
+#name: Check linker stubs with indirect calls handle BTI (shared lib).
+#source: bti-far.s
+#target: [check_shared_lib_support]
+#as: -mabi=lp64
+#ld: -shared -T bti-far.ld
+#objdump: -dr
+
+[^:]*: *file format elf64-.*aarch64
+
+
+Disassembly of section \.plt:
+
+0000000000018000 <\.plt>:
+   18000:	d503245f 	bti	c
+   18004:	a9bf7bf0 	stp	x16, x30, \[sp, #-16\]!
+   18008:	900000d0 	adrp	x16, 30000 <_GLOBAL_OFFSET_TABLE_>
+   1800c:	f9400e11 	ldr	x17, \[x16, #24\]
+   18010:	91006210 	add	x16, x16, #0x18
+   18014:	d61f0220 	br	x17
+   18018:	d503201f 	nop
+   1801c:	d503201f 	nop
+
+0000000000018020 <foo@plt>:
+   18020:	900000d0 	adrp	x16, 30000 <_GLOBAL_OFFSET_TABLE_>
+   18024:	f9401211 	ldr	x17, \[x16, #32\]
+   18028:	91008210 	add	x16, x16, #0x20
+   1802c:	d61f0220 	br	x17
+   18030:	14000004 	b	18040 <__foo_bti_veneer\+0x8>
+   18034:	d503201f 	nop
+
+0000000000018038 <__foo_bti_veneer>:
+   18038:	d503245f 	bti	c
+   1803c:	17fffff9 	b	18020 <foo@plt>
+
+Disassembly of section \.text:
+
+0000000000020000 <_start>:
+   20000:	97ffe008 	bl	18020 <foo@plt>
+   20004:	94000007 	bl	20020 <___veneer>
+   20008:	94000001 	bl	2000c <baz>
+
+000000000002000c <baz>:
+   2000c:	d65f03c0 	ret
+   20010:	1400000a 	b	20038 <___veneer\+0x18>
+   20014:	d503201f 	nop
+
+0000000000020018 <___bti_veneer>:
+   20018:	d503245f 	bti	c
+   2001c:	17fffffc 	b	2000c <baz>
+
+0000000000020020 <___veneer>:
+   20020:	90091910 	adrp	x16, 12340000 <foo>
+   20024:	91012210 	add	x16, x16, #0x48
+   20028:	d61f0200 	br	x16
+	\.\.\.
+
+Disassembly of section \.far:
+
+0000000012340000 <foo>:
+    12340000:	9400000c 	bl	12340030 <___veneer>
+
+0000000012340004 <bar>:
+    12340004:	9400000b 	bl	12340030 <___veneer>
+    12340008:	94000004 	bl	12340018 <__foo_veneer>
+    1234000c:	00000000 	udf	#0
+    12340010:	14000010 	b	12340050 <___bti_veneer\+0x8>
+    12340014:	d503201f 	nop
+
+0000000012340018 <__foo_veneer>:
+    12340018:	90f6e6d0 	adrp	x16, 18000 <\.plt>
+    1234001c:	9100e210 	add	x16, x16, #0x38
+    12340020:	d61f0200 	br	x16
+	\.\.\.
+
+0000000012340030 <___veneer>:
+    12340030:	90f6e710 	adrp	x16, 20000 <_start>
+    12340034:	91006210 	add	x16, x16, #0x18
+    12340038:	d61f0200 	br	x16
+	\.\.\.
+
+0000000012340048 <___bti_veneer>:
+    12340048:	d503245f 	bti	c
+    1234004c:	17ffffee 	b	12340004 <bar>
diff --git a/ld/testsuite/ld-aarch64/bti-far-2.d b/ld/testsuite/ld-aarch64/bti-far-2.d
new file mode 100644
index 00000000000..b859e6ce399
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-far-2.d
@@ -0,0 +1,62 @@
+#name: Check linker stubs with indirect calls handle BTI (exe).
+#source: bti-far.s
+#as: -mabi=lp64
+#ld: -T bti-far.ld
+#objdump: -dr
+
+[^:]*: *file format elf64-.*aarch64
+
+
+Disassembly of section \.text:
+
+0000000000020000 <_start>:
+   20000:	9400000e 	bl	20038 <__foo_veneer>
+   20004:	94000007 	bl	20020 <___veneer>
+   20008:	94000001 	bl	2000c <baz>
+
+000000000002000c <baz>:
+   2000c:	d65f03c0 	ret
+   20010:	14000010 	b	20050 <__foo_veneer\+0x18>
+   20014:	d503201f 	nop
+
+0000000000020018 <___bti_veneer>:
+   20018:	d503245f 	bti	c
+   2001c:	17fffffc 	b	2000c <baz>
+
+0000000000020020 <___veneer>:
+   20020:	90091910 	adrp	x16, 12340000 <foo>
+   20024:	9100e210 	add	x16, x16, #0x38
+   20028:	d61f0200 	br	x16
+	\.\.\.
+
+0000000000020038 <__foo_veneer>:
+   20038:	90091910 	adrp	x16, 12340000 <foo>
+   2003c:	91006210 	add	x16, x16, #0x18
+   20040:	d61f0200 	br	x16
+	\.\.\.
+
+Disassembly of section \.far:
+
+0000000012340000 <foo>:
+    12340000:	94000008 	bl	12340020 <___veneer>
+
+0000000012340004 <bar>:
+    12340004:	94000007 	bl	12340020 <___veneer>
+    12340008:	97fffffe 	bl	12340000 <foo>
+    1234000c:	00000000 	udf	#0
+    12340010:	1400000c 	b	12340040 <___bti_veneer\+0x8>
+    12340014:	d503201f 	nop
+
+0000000012340018 <__foo_bti_veneer>:
+    12340018:	d503245f 	bti	c
+    1234001c:	17fffff9 	b	12340000 <foo>
+
+0000000012340020 <___veneer>:
+    12340020:	90f6e710 	adrp	x16, 20000 <_start>
+    12340024:	91006210 	add	x16, x16, #0x18
+    12340028:	d61f0200 	br	x16
+	\.\.\.
+
+0000000012340038 <___bti_veneer>:
+    12340038:	d503245f 	bti	c
+    1234003c:	17fffff2 	b	12340004 <bar>
diff --git a/ld/testsuite/ld-aarch64/bti-far.ld b/ld/testsuite/ld-aarch64/bti-far.ld
new file mode 100644
index 00000000000..214b8cb919e
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-far.ld
@@ -0,0 +1,15 @@
+OUTPUT_ARCH(aarch64)
+ENTRY(_start)
+SECTIONS
+{
+  . = 0x10000;
+  .rela.plt       : { *(.rela.plt) *(.rela.iplt) }
+  . = 0x18000;
+  .plt            : { *(.plt) *(.iplt) }
+  . = 0x20000;
+  .text           : { *(.text) }
+  . = 0x30000;
+  .got            : { *(.got) *(.got.plt) }
+  . = 0x12340000;
+  .far            : { *(.far) }
+}
diff --git a/ld/testsuite/ld-aarch64/bti-far.s b/ld/testsuite/ld-aarch64/bti-far.s
new file mode 100644
index 00000000000..20cffd225cb
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-far.s
@@ -0,0 +1,29 @@
+	.text
+	.global	_start
+	.type	_start, %function
+_start:
+	bl foo
+	bl bar
+	bl baz
+baz:
+	ret
+
+	.section	.far,"ax",@progbits
+	.global	foo
+	.type	foo, %function
+foo:
+	bl baz
+bar:
+	bl baz
+	bl foo
+
+	.section	.note.gnu.property,"a"
+	.align	3
+	.word	4
+	.word	16
+	.word	5
+	.string	"GNU"
+	.word	0xc0000000
+	.word	4
+	.word	1
+	.align	3