[BFD, LD, AArch64, 2/3] Add --force-bti to enable BTI and to select BTI enabled PLTs

This is part of the patch series to add support for BTI and
PAC in AArch64 linker.

1) This patch adds a new ld command line option: --force-bti.
In the presence of this option, the linker enables BTI with the
GNU_PROPERTY_AARCH64_FEATURE_1_BTI feature. This gives out warning
in case of missing gnu notes for BTI in inputs.
2) It also defines a new set of BTI enabled PLTs. These are used either
when all the inputs are marked with GNU_PROPERTY_AARCH64_FEATURE_1_BTI
or when the new --force-bti option is used. This required adding new
fields in elf_aarch64_link_hash_table so that we could make the PLT
related information more generic.
3) It also defines a dynamic tag DT_AARCH64_BTI_PLT. The linker uses
this whenever it picks BTI enabled PLTs.
All these are made according to the new AArch64 ELF ABI
https://developer.arm.com/docs/ihi0056/latest/elf-for-the-arm-64-bit-architecture-aarch64-abi-2018q4

*** bfd/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>
	    Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* bfd-in.h (aarch64_plt_type, aarch64_enable_bti_type): New.
	(aarch64_bti_pac_info): New.
	(bfd_elf64_aarch64_set_options): Add aarch64_bti_pac_info argument.
	(bfd_elf32_aarch64_set_options): Likewise.
	* bfd-in2.h: Regenerate
	* elfnn-aarch64.c (PLT_BTI_ENTRY_SIZE): New.
	(PLT_BTI_SMALL_ENTRY_SIZE, PLT_BTI_TLSDESC_ENTRY_SIZE): New.
	(elfNN_aarch64_small_plt0_bti_entry): New.
	(elfNN_aarch64_small_plt_bti_entry): New.
	(elfNN_aarch64_tlsdesc_small_plt_bti_entry): New.
	(elf_aarch64_obj_tdata): Add no_bti_warn and plt_type fields.
	(elf_aarch64_link_hash_table): Add plt0_entry, plt_entry and
	tlsdesc_plt_entry_size fields.
	(elfNN_aarch64_link_hash_table_create): Initialise the new fields.
	(setup_plt_values): New helper function.
	(bfd_elfNN_aarch64_set_options): Use new bp_info to set plt sizes and
	bti enable type.
	(elfNN_aarch64_allocate_dynrelocs): Use new size members instead of
	fixed macros.
	(elfNN_aarch64_size_dynamic_sections): Likewise and add checks.
	(elfNN_aarch64_create_small_pltn_entry): Use new generic pointers
	to plt stubs instead of fixed ones and update filling them according
	to the need for bti.
	(elfNN_aarch64_init_small_plt0_entry): Likewise.
	(elfNN_aarch64_finish_dynamic_sections): Likewise.
	(get_plt_type, elfNN_aarch64_get_synthetic_symtab): New.
	(elfNN_aarch64_plt_sym_val): Update size accordingly.
	(elfNN_aarch64_link_setup_gnu_properties): Set up plts if BTI GNU NOTE
	is set.
	(bfd_elfNN_get_synthetic_symtab): Define.
	(elfNN_aarch64_merge_gnu_properties): Give out warning with --force-bti
	and mising BTI NOTE SECTION.

*** binutils/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>
	    Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* readelf.c (get_aarch64_dynamic_type): New.
	(get_dynamic_type): Use above for EM_AARCH64.
	(dynamic_section_aarch64_val): New.
	(process_dynamic_section): Use above for EM_AARCH64.

*** include/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>
	    Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* elf/aarch64.h (DT_AARCH64_BTI_PLT): New.

*** ld/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>
	    Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* NEWS: Document --force-bti.
	* emultempl/aarch64elf.em (plt_type, bti_type, OPTION_FORCE_BTI): New.
	(PARSE_AND_LIST_SHORTOPTS, PARSE_AND_LIST_OPTIONS): Add force-bti.
	(PARSE_AND_LIST_ARGS_CASES): Handle OPTION_FORCE_BTI.
	* testsuite/ld-aarch64/aarch64-elf.exp: Add all the tests below.
	* testsuite/ld-aarch64/bti-plt-1.d: New test.
	* testsuite/ld-aarch64/bti-plt-1.s: New test.
	* testsuite/ld-aarch64/bti-plt-2.s: New test.
	* testsuite/ld-aarch64/bti-plt-2.d: New test.
	* testsuite/ld-aarch64/bti-plt-3.d: New test.
	* testsuite/ld-aarch64/bti-plt-4.d: New test.
	* testsuite/ld-aarch64/bti-plt-5.d: New test.
	* testsuite/ld-aarch64/bti-plt-6.d: New test.
	* testsuite/ld-aarch64/bti-plt-7.d: New test.
	* testsuite/ld-aarch64/bti-plt-so.s: New test.
	* testsuite/ld-aarch64/bti-plt.ld: New test.

12 files changed, 252 insertions, 0 deletions

diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index c6fefbb..906534b 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -374,6 +374,8 @@ run_dump_test_lp64 "pie-bind-locally"
 run_dump_test "property-bti-pac1"
 run_dump_test "property-bti-pac2"
 run_dump_test "property-bti-pac3"
+run_dump_test "bti-plt-1"
+run_dump_test "bti-plt-2"
 
 set aarch64elflinktests {
   {"ld-aarch64/so with global symbol" "-shared" "" "" {copy-reloc-so.s}
@@ -389,6 +391,14 @@ set aarch64elflinktests {
   {"ld-aarch64/func sym hash opt for exe"
    "-e0 --hash-style=gnu tmpdir/func-in-so.so" "" ""
     {func-sym-hash-opt.s} {{readelf --dyn-sym func-sym-hash-opt.d}} "hash-opt"}
+  {"Build bti-plt-so for PLT tests" "-shared" "" "" {bti-plt-so.s}
+    {} "libbti-plt-so.so"}
 }
 
 run_ld_link_tests $aarch64elflinktests
+
+run_dump_test "bti-plt-3"
+run_dump_test "bti-plt-4"
+run_dump_test "bti-plt-5"
+run_dump_test "bti-plt-6"
+run_dump_test "bti-plt-7"
diff --git a/ld/testsuite/ld-aarch64/bti-plt-1.d b/ld/testsuite/ld-aarch64/bti-plt-1.d
new file mode 100644
index 0000000..b7b58a8
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-1.d
@@ -0,0 +1,32 @@
+#name: Check --force-bti emits BTI PLT (shared)
+#source: bti-plt-1.s
+#as: -mabi=lp64
+#ld: -shared --force-bti -T bti-plt.ld
+#objdump: -dr -j .plt
+
+[^:]*: *file format elf64-.*aarch64
+
+Disassembly of section \.plt:
+
+[0-9]+ <.*>:
+.*:	d503245f 	bti	c
+.*:	a9bf7bf0 	stp	x16, x30, \[sp, #-16\]!
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9400e11 	ldr	x17, \[x16, #24\]
+.*:	91006210 	add	x16, x16, #0x18
+.*:	d61f0220 	br	x17
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+
+[0-9]+ <.*>:
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401211 	ldr	x17, \[x16, #32\]
+.*:	91008210 	add	x16, x16, #0x20
+.*:	d61f0220 	br	x17
+
+[0-9]+ <.*>:
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401611 	ldr	x17, \[x16, #40\]
+.*:	9100a210 	add	x16, x16, #0x28
+.*:	d61f0220 	br	x17
diff --git a/ld/testsuite/ld-aarch64/bti-plt-1.s b/ld/testsuite/ld-aarch64/bti-plt-1.s
new file mode 100644
index 0000000..78e1aaa
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-1.s
@@ -0,0 +1,21 @@
+	.text
+	.globl _start
+	.type _start,@function
+_start:
+	bl foo
+	bl bar
+	.section ".note.gnu.property", "a"
+	.p2align 3
+	.long 1f - 0f		/* name length */
+	.long 5f - 2f		/* data length */
+	.long 5			/* note type */
+0:	.asciz "GNU"		/* vendor name */
+1:
+	.p2align 3
+2:	.long 0xc0000000	/* pr_type.  */
+	.long 4f - 3f		/* pr_datasz.  */
+3:
+	.long 0x1		/* BTI.  */
+4:
+	.p2align 3
+5:
diff --git a/ld/testsuite/ld-aarch64/bti-plt-2.d b/ld/testsuite/ld-aarch64/bti-plt-2.d
new file mode 100644
index 0000000..c26e47a
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-2.d
@@ -0,0 +1,11 @@
+#name: Check --force-bti emits BTI feature (shared)
+#source: bti-plt-1.s
+#source: bti-plt-2.s
+#as: -mabi=lp64
+#ld: -shared --force-bti -T bti-plt.ld
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+  Owner                 Data size	Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: BTI
diff --git a/ld/testsuite/ld-aarch64/bti-plt-2.s b/ld/testsuite/ld-aarch64/bti-plt-2.s
new file mode 100644
index 0000000..fff945c
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-2.s
@@ -0,0 +1,21 @@
+	.text
+	.globl _start
+	.type _start,@function
+func2:
+	bl foo2
+	bl bar2
+	.section ".note.gnu.property", "a"
+	.p2align 3
+	.long 1f - 0f		/* name length */
+	.long 5f - 2f		/* data length */
+	.long 5			/* note type */
+0:	.asciz "GNU"		/* vendor name */
+1:
+	.p2align 3
+2:	.long 0xc0000000	/* pr_type.  */
+	.long 4f - 3f		/* pr_datasz.  */
+3:
+	.long 0x1		/* BTI.  */
+4:
+	.p2align 3
+5:
diff --git a/ld/testsuite/ld-aarch64/bti-plt-3.d b/ld/testsuite/ld-aarch64/bti-plt-3.d
new file mode 100644
index 0000000..0d4c467
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-3.d
@@ -0,0 +1,34 @@
+#name: Check --force-bti emits BTI PLT (exec)
+#source: bti-plt-1.s
+#as: -mabi=lp64
+#ld: --force-bti -e _start -T bti-plt.ld -L./tmpdir -lbti-plt-so
+#objdump: -dr -j .plt
+
+[^:]*: *file format elf64-.*aarch64
+
+Disassembly of section \.plt:
+
+[0-9]+ <.*>:
+.*:	d503245f 	bti	c
+.*:	a9bf7bf0 	stp	x16, x30, \[sp, #-16\]!
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9400e11 	ldr	x17, \[x16, #24\]
+.*:	91006210 	add	x16, x16, #0x18
+.*:	d61f0220 	br	x17
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+
+[0-9]+ <.*>:
+.*:	d503245f 	bti	c
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401211 	ldr	x17, \[x16, #32\]
+.*:	91008210 	add	x16, x16, #0x20
+.*:	d61f0220 	br	x17
+
+[0-9]+ <.*>:
+.*:	d503245f 	bti	c
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401611 	ldr	x17, \[x16, #40\]
+.*:	9100a210 	add	x16, x16, #0x28
+.*:	d61f0220 	br	x17
diff --git a/ld/testsuite/ld-aarch64/bti-plt-4.d b/ld/testsuite/ld-aarch64/bti-plt-4.d
new file mode 100644
index 0000000..90aeed2
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-4.d
@@ -0,0 +1,10 @@
+#name: Check --force-bti emits BTI feature (exec)
+#source: bti-plt-1.s
+#as: -mabi=lp64
+#ld: --force-bti -e _start -T bti-plt.ld -L./tmpdir -lbti-plt-so
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+  Owner                 Data size	Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: BTI
diff --git a/ld/testsuite/ld-aarch64/bti-plt-5.d b/ld/testsuite/ld-aarch64/bti-plt-5.d
new file mode 100644
index 0000000..01231b6
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-5.d
@@ -0,0 +1,28 @@
+#name: BTI PLT with only GNU PROP
+#source: property-bti-pac1.s
+#as: -mabi=lp64 -defsym __property_bti__=1
+#ld: -e _start -L./tmpdir -lbti-plt-so
+#objdump: -dr -j .plt
+#target: *linux*
+
+[^:]*: *file format elf64-.*aarch64
+
+Disassembly of section \.plt:
+
+[0-9a-f]+ <.*>:
+.*:	d503245f 	bti	c
+.*:	a9bf7bf0 	stp	x16, x30, \[sp, #-16\]!
+.*:	90000090 	adrp	x16, 410000 <_start\+0xfd28>
+.*:	f9421611 	ldr	x17, \[x16, #1064\]
+.*:	9110a210 	add	x16, x16, #0x428
+.*:	d61f0220 	br	x17
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+
+[0-9a-f]+ <.*>:
+.*:	d503245f 	bti	c
+.*:	90000090 	adrp	x16, 410000 <_start\+0xfd28>
+.*:	f9421a11 	ldr	x17, \[x16, #1072\]
+.*:	9110c210 	add	x16, x16, #0x430
+.*:	d61f0220 	br	x17
diff --git a/ld/testsuite/ld-aarch64/bti-plt-6.d b/ld/testsuite/ld-aarch64/bti-plt-6.d
new file mode 100644
index 0000000..c7d5169
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-6.d
@@ -0,0 +1,15 @@
+#name: Warn with one missing GNU NOTE BTI input
+#source: property-bti-pac1.s
+#source: property-bti-pac2.s
+#as: -mabi=lp64 -defsym __property_pac__=1
+#ld: -shared --force-bti
+#warning: .*: warning: BTI turned on by --force-bti.*$
+#readelf: -n
+
+# Should warn about the missing input BTI NOTE but should
+# still mark output as BTI
+
+Displaying notes found in: .note.gnu.property
+  Owner                 Data size	Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: BTI, PAC
diff --git a/ld/testsuite/ld-aarch64/bti-plt-7.d b/ld/testsuite/ld-aarch64/bti-plt-7.d
new file mode 100644
index 0000000..625f284
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-7.d
@@ -0,0 +1,15 @@
+#name: Warn when neither inputs has GNU NOTE BTI
+#source: property-bti-pac1.s
+#source: plt_mapping_symbol.s
+#as: -mabi=lp64
+#ld: -shared --force-bti
+#warning: .*: warning: BTI turned on by --force-bti.*$
+#readelf: -n
+
+# Should warn about the missing input BTI NOTE but should
+# still mark output as BTI
+
+Displaying notes found in: .note.gnu.property
+  Owner                 Data size	Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: BTI
diff --git a/ld/testsuite/ld-aarch64/bti-plt-so.s b/ld/testsuite/ld-aarch64/bti-plt-so.s
new file mode 100644
index 0000000..2c11356
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt-so.s
@@ -0,0 +1,41 @@
+	.global	foo
+	.type	foo, %function
+foo:
+	sub	sp, sp, #16
+	mov	w0, 9
+	str	w0, [sp, 12]
+	ldr	w0, [sp, 12]
+	add	w0, w0, 4
+	str	w0, [sp, 12]
+	nop
+	add	sp, sp, 16
+	ret
+	.size	foo, .-foo
+	.global	bar
+	.type	bar, %function
+bar:
+	sub	sp, sp, #16
+	mov	w0, 9
+	str	w0, [sp, 12]
+	ldr	w0, [sp, 12]
+	add	w0, w0, 4
+	str	w0, [sp, 12]
+	nop
+	add	sp, sp, 16
+	ret
+	.size	bar, .-bar
+	.section ".note.gnu.property", "a"
+	.p2align 3
+	.long 1f - 0f		/* name length */
+	.long 5f - 2f		/* data length */
+	.long 5			/* note type */
+0:	.asciz "GNU"		/* vendor name */
+1:
+	.p2align 3
+2:	.long 0xc0000000	/* pr_type.  */
+	.long 4f - 3f		/* pr_datasz.  */
+3:
+	.long 0x1		/* BTI.  */
+4:
+	.p2align 3
+5:
diff --git a/ld/testsuite/ld-aarch64/bti-plt.ld b/ld/testsuite/ld-aarch64/bti-plt.ld
new file mode 100644
index 0000000..8682623
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-plt.ld
@@ -0,0 +1,14 @@
+OUTPUT_ARCH(aarch64)
+ENTRY(_start)
+SECTIONS
+{
+  . = 0x10000;
+  .rela.plt       : { *(.rela.plt) *(.rela.iplt) }
+  . = 0x18000;
+  .plt            : { *(.plt) *(.iplt) }
+  . = 0x20000;
+  .text           : { *(.text) }
+  . = 0x28000;
+  .got            : { *(.got) *(.got.plt) }
+  .ARM.attributes 0 : { *(.ARM.atttributes) }
+}