[BFD, LD, AArch64, 3/3] Add --pac-plt to enable PLTs protected with PAC.

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

1) This patch adds new definitions of PAC enabled PLTs
and both BTI and PAC enabled PLTs.
2) It also defines the new dynamic tag DT_AARCH64_PAC_PLT
for the PAC enabled PLTs.
3) This patch adds a new ld command line option: --pac-plt.
In the presence of this option, the linker uses the PAC
enabled PLTs and marks with DT_AARCH64_PAC_PLT.
4) In case both BTI and PAC are enabled the linker should
pick PLTs enabled with both and also use dynamic tags for both.
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>

	* elfnn-aarch64.c (PLT_PAC_ENTRY_SIZE, PLT_PAC_SMALL_ENTRY_SIZE): New.
	(PLT_BTI_PAC_ENTRY_SIZE, PLT_BTI_PAC_SMALL_ENTRY_SIZE): New.
	(setup_plt_values): Account for PAC or PAC and BTI enabled PLTs.
	(elfNN_aarch64_size_dynamic_sections): Add checks for PLT_BTI_PAC
	and PLT_PAC_PLT.
	(elfNN_aarch64_finish_dynamic_sections): Account for PLT_BTI_PAC.
	(get_plt_type): Add case for DT_AARCH64_PAC_PLT.
	(elfNN_aarch64_plt_sym_val): Add cases for PLT_BTI_PAC and PLT_PAC.

*** binutils/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* readelf.c (get_aarch64_dynamic_type): Add case for
	DT_AARCH64_PAC_PLT.
	(dynamic_section_aarch64_val): Likewise.

*** include/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* elf/aarch64.h (DT_AARCH64_PAC_PLT): New.

*** ld/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* NEWS: Document --pac-plt.
	* emultempl/aarch64elf.em (OPTION_PAC_PLT): New.
	(PARSE_AND_LIST_LONGOPTS, PARSE_AND_LIST_OPTIONS): Add pac-plt.
	(PARSE_AND_LIST_ARGS_CASES): Handle OPTION_PAC_PLT.
	* testsuite/ld-aarch64/aarch64-elf.exp: Add the following tests.
	* testsuite/ld-aarch64/bti-pac-plt-1.d: New test.
	* testsuite/ld-aarch64/bti-pac-plt-2.d: New test.
	* testsuite/ld-aarch64/pac-plt-1.d: New test.
	* testsuite/ld-aarch64/pac-plt-2.d: New test.
	* testsuite/ld-aarch64/bti-plt-1.s: Add .ifndef directive.

9 files changed, 156 insertions, 0 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 151877d..d37865b 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,4 +1,17 @@
 2019-03-13  Sudakshina Das  <sudi.das@arm.com>
+
+	* NEWS: Document --pac-plt.
+	* emultempl/aarch64elf.em (OPTION_PAC_PLT): New.
+	(PARSE_AND_LIST_LONGOPTS, PARSE_AND_LIST_OPTIONS): Add pac-plt.
+	(PARSE_AND_LIST_ARGS_CASES): Handle OPTION_PAC_PLT.
+	* testsuite/ld-aarch64/aarch64-elf.exp: Add the following tests.
+	* testsuite/ld-aarch64/bti-pac-plt-1.d: New test.
+	* testsuite/ld-aarch64/bti-pac-plt-2.d: New test.
+	* testsuite/ld-aarch64/pac-plt-1.d: New test.
+	* testsuite/ld-aarch64/pac-plt-2.d: New test.
+	* testsuite/ld-aarch64/bti-plt-1.s: Add .ifndef directive.
+
+2019-03-13  Sudakshina Das  <sudi.das@arm.com>
 	    Szabolcs Nagy  <szabolcs.nagy@arm.com>
 
 	* NEWS: Document --force-bti.
diff --git a/ld/NEWS b/ld/NEWS
index ed8dfc5..597845a 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -14,6 +14,8 @@ Changes in 2.33:
   on output while warning about missing GNU_PROPERTY_AARCH64_FEATURE_1_BTI
   on inputs and use PLTs protected with BTI.
 
+* Add --pac-plt for AArch64 to pick PAC enabled PLTs.
+
 Changes in 2.32:
 
 * Report property change in linker map file when merging GNU properties.
diff --git a/ld/emultempl/aarch64elf.em b/ld/emultempl/aarch64elf.em
index 02243d9..bfe8d1b 100644
--- a/ld/emultempl/aarch64elf.em
+++ b/ld/emultempl/aarch64elf.em
@@ -373,6 +373,7 @@ PARSE_AND_LIST_PROLOGUE='
 #define OPTION_FIX_ERRATUM_843419	314
 #define OPTION_NO_APPLY_DYNAMIC_RELOCS	315
 #define OPTION_FORCE_BTI		316
+#define OPTION_PAC_PLT			317
 '
 
 PARSE_AND_LIST_SHORTOPTS=p
@@ -387,6 +388,7 @@ PARSE_AND_LIST_LONGOPTS='
   { "fix-cortex-a53-843419", no_argument, NULL, OPTION_FIX_ERRATUM_843419},
   { "no-apply-dynamic-relocs", no_argument, NULL, OPTION_NO_APPLY_DYNAMIC_RELOCS},
   { "force-bti", no_argument, NULL, OPTION_FORCE_BTI},
+  { "pac-plt", no_argument, NULL, OPTION_PAC_PLT},
 '
 
 PARSE_AND_LIST_OPTIONS='
@@ -408,6 +410,7 @@ PARSE_AND_LIST_OPTIONS='
   fprintf (file, _("  --fix-cortex-a53-843419      Fix erratum 843419\n"));
   fprintf (file, _("  --no-apply-dynamic-relocs    Do not apply link-time values for dynamic relocations\n"));
   fprintf (file, _("  --force-bti                  Turn on Branch Target Identification mechanism and generate PLTs with BTI. Generate warnings for missing BTI on inputs\n"));
+  fprintf (file, _("  --pac-plt                    Protect PLTs with Pointer Authentication.\n"));
 '
 
 PARSE_AND_LIST_ARGS_CASES='
@@ -444,6 +447,10 @@ PARSE_AND_LIST_ARGS_CASES='
       bti_type = BTI_WARN;
       break;
 
+    case OPTION_PAC_PLT:
+      plt_type |= PLT_PAC;
+      break;
+
     case OPTION_STUBGROUP_SIZE:
       {
 	const char *end;
diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 906534b..12c2d97 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -402,3 +402,8 @@ run_dump_test "bti-plt-4"
 run_dump_test "bti-plt-5"
 run_dump_test "bti-plt-6"
 run_dump_test "bti-plt-7"
+
+run_dump_test "pac-plt-1"
+run_dump_test "pac-plt-2"
+run_dump_test "bti-pac-plt-1"
+run_dump_test "bti-pac-plt-2"
diff --git a/ld/testsuite/ld-aarch64/bti-pac-plt-1.d b/ld/testsuite/ld-aarch64/bti-pac-plt-1.d
new file mode 100644
index 0000000..8d780ca
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-pac-plt-1.d
@@ -0,0 +1,34 @@
+#source: bti-plt-1.s
+#as: -mabi=lp64
+#ld: -shared --force-bti --pac-plt -T bti-plt.ld
+#objdump: -dr -j .plt
+
+[^:]*: *file format elf64-.*aarch64
+
+Disassembly of section \.plt:
+
+[0-9a-f]+ <.*>:
+.*:	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
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+
+[0-9a-f]+ <.*>:
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401211 	ldr	x17, \[x16, #32\]
+.*:	91008210 	add	x16, x16, #0x20
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
+
+[0-9a-f]+ <.*>:
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401611 	ldr	x17, \[x16, #40\]
+.*:	9100a210 	add	x16, x16, #0x28
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
diff --git a/ld/testsuite/ld-aarch64/bti-pac-plt-2.d b/ld/testsuite/ld-aarch64/bti-pac-plt-2.d
new file mode 100644
index 0000000..d1264ea
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/bti-pac-plt-2.d
@@ -0,0 +1,36 @@
+#source: bti-plt-1.s
+#as: -mabi=lp64
+#ld: --force-bti --pac-plt -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
+.*:	d503219f 	autia1716
+.*:	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
+.*:	d503219f 	autia1716
+.*:	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
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
diff --git a/ld/testsuite/ld-aarch64/bti-plt-1.s b/ld/testsuite/ld-aarch64/bti-plt-1.s
index 78e1aaa..b798ca4 100644
--- a/ld/testsuite/ld-aarch64/bti-plt-1.s
+++ b/ld/testsuite/ld-aarch64/bti-plt-1.s
@@ -4,6 +4,7 @@
 _start:
 	bl foo
 	bl bar
+.ifndef __guard_property_bti__
 	.section ".note.gnu.property", "a"
 	.p2align 3
 	.long 1f - 0f		/* name length */
@@ -19,3 +20,4 @@ _start:
 4:
 	.p2align 3
 5:
+.endif
diff --git a/ld/testsuite/ld-aarch64/pac-plt-1.d b/ld/testsuite/ld-aarch64/pac-plt-1.d
new file mode 100644
index 0000000..47be949
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/pac-plt-1.d
@@ -0,0 +1,33 @@
+#source: bti-plt-1.s
+#as: -mabi=lp64 --defsym __guard_property_bti__=1
+#ld: -shared --pac-plt -T bti-plt.ld
+#objdump: -dr -j .plt
+
+[^:]*: *file format elf64-.*aarch64
+
+Disassembly of section \.plt:
+
+[0-9]+ <.*>:
+.*:	a9bf7bf0 	stp	x16, x30, \[sp, #-16\]!
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9400e11 	ldr	x17, \[x16, #24\]
+.*:	91006210 	add	x16, x16, #0x18
+.*:	d503219f 	autia1716
+.*:	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
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
+
+[0-9]+ <.*>:
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401611 	ldr	x17, \[x16, #40\]
+.*:	9100a210 	add	x16, x16, #0x28
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
diff --git a/ld/testsuite/ld-aarch64/pac-plt-2.d b/ld/testsuite/ld-aarch64/pac-plt-2.d
new file mode 100644
index 0000000..42bfdca
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/pac-plt-2.d
@@ -0,0 +1,24 @@
+#source: tls-desc-ie.s
+#ld: -shared --pac-plt -T bti-plt.ld
+#objdump: -dr -j .plt
+#...
+Disassembly of section .plt:
+
+0000000000018000 \<.plt\>:
+.*:	a9bf7bf0 	stp	x16, x30, \[sp, #-16\]!
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401a11 	ldr	x17, \[x16, #48\]
+.*:	9100c210 	add	x16, x16, #0x30
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+.*:	d503201f 	nop
+
+
+0000000000018024 \<__tls_get_addr@plt\>:
+.*:	90000090 	adrp	x16, 28000 <_GLOBAL_OFFSET_TABLE_>
+.*:	f9401e11 	ldr	x17, \[x16, #56\]
+.*:	9100e210 	add	x16, x16, #0x38
+.*:	d503219f 	autia1716
+.*:	d61f0220 	br	x17