[AArch64, 4/6] Enable BTI: Add new <type> to -mbranch-protection.

This patch is part of a series that enables ARMv8.5-A in GCC and
adds Branch Target Identification Mechanism.

This pass updates the CLI of -mbranch-protection to add "bti" as a new
type of branch protection and also add it its definition of "none" and
"standard". The option does not really do anything functional.
The functional changes are in the next patch. I am initializing the target
variable aarch64_enable_bti to 2 since I am also adding a configure option
in a later patch and a value different from 0 and 1 would help identify if its
already been updated.

*** gcc/ChangeLog ***

2018-01-09  Sudakshina Das  <sudi.das@arm.com>

	* config/aarch64/aarch64-protos.h (aarch64_bti_enabled): Declare.
	* config/aarch64/aarch64.c (aarch64_handle_no_branch_protection):
	Disable bti for -mbranch-protection=none.
	(aarch64_handle_standard_branch_protection): Enable bti for
	-mbranch-protection=standard.
	(aarch64_handle_bti_protection): Enable bti for "bti" in the string to
	-mbranch-protection.
	(aarch64_bti_enabled): Check if bti is enabled.
	* config/aarch64/aarch64.opt: Declare target variable.
	* doc/invoke.texi: Add bti to the -mbranch-protection documentation.

From-SVN: r267768

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index bd065bc471621fb4c12f885f4ae5c4e316cd5f15..0bc36756e4ae74a40b2cae8247c83e4d5b542979 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2018-01-09  Sudakshina Das  <sudi.das@arm.com>
+
+       * config/aarch64/aarch64-protos.h (aarch64_bti_enabled): Declare.
+       * config/aarch64/aarch64.c (aarch64_handle_no_branch_protection):
+       Disable bti for -mbranch-protection=none.
+       (aarch64_handle_standard_branch_protection): Enable bti for
+       -mbranch-protection=standard.
+       (aarch64_handle_bti_protection): Enable bti for "bti" in the string to
+       -mbranch-protection.
+       (aarch64_bti_enabled): Check if bti is enabled.
+       * config/aarch64/aarch64.opt: Declare target variable.
+       * doc/invoke.texi: Add bti to the -mbranch-protection documentation.
+
 2018-01-09  Sudakshina Das  <sudi.das@arm.com>
 
        * config/aarch64/aarch64.c (aarch64_expand_prologue): Use new

diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index 209c09be669cc139d82d5c7aedb6e59292c50f07..3e3ad14d3232c68c9988a47795e23a474eaf8421 100644 (file)
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -521,6 +521,7 @@ void aarch64_register_pragmas (void);
 void aarch64_relayout_simd_types (void);
 void aarch64_reset_previous_fndecl (void);
 bool aarch64_return_address_signing_enabled (void);
+bool aarch64_bti_enabled (void);
 void aarch64_save_restore_target_globals (tree);
 void aarch64_addti_scratch_regs (rtx, rtx, rtx *,
                                 rtx *, rtx *,

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 152875d9dacf298052416cd871c587c756256645..47569b841f9d51ed58c49615fbfc9ae09107ef2f 100644 (file)
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -1200,6 +1200,7 @@ static enum aarch64_parse_opt_result
 aarch64_handle_no_branch_protection (char* str, char* rest)
 {
   aarch64_ra_sign_scope = AARCH64_FUNCTION_NONE;
+  aarch64_enable_bti = 0;
   if (rest)
     {
       error ("unexpected %<%s%> after %<%s%>", rest, str);
@@ -1212,6 +1213,7 @@ static enum aarch64_parse_opt_result
 aarch64_handle_standard_branch_protection (char* str, char* rest)
 {
   aarch64_ra_sign_scope = AARCH64_FUNCTION_NON_LEAF;
+  aarch64_enable_bti = 1;
   if (rest)
     {
       error ("unexpected %<%s%> after %<%s%>", rest, str);
@@ -1236,6 +1238,14 @@ aarch64_handle_pac_ret_leaf (char* str ATTRIBUTE_UNUSED,
   return AARCH64_PARSE_OK;
 }
 
+static enum aarch64_parse_opt_result
+aarch64_handle_bti_protection (char* str ATTRIBUTE_UNUSED,
+                                   char* rest ATTRIBUTE_UNUSED)
+{
+  aarch64_enable_bti = 1;
+  return AARCH64_PARSE_OK;
+}
+
 static const struct aarch64_branch_protect_type aarch64_pac_ret_subtypes[] = {
   { "leaf", aarch64_handle_pac_ret_leaf, NULL, 0 },
   { NULL, NULL, NULL, 0 }
@@ -1246,6 +1256,7 @@ static const struct aarch64_branch_protect_type aarch64_branch_protect_types[] =
   { "standard", aarch64_handle_standard_branch_protection, NULL, 0 },
   { "pac-ret", aarch64_handle_pac_ret_protection, aarch64_pac_ret_subtypes,
     ARRAY_SIZE (aarch64_pac_ret_subtypes) },
+  { "bti", aarch64_handle_bti_protection, NULL, 0 },
   { NULL, NULL, NULL, 0 }
 };
 
@@ -4725,6 +4736,13 @@ aarch64_return_address_signing_enabled (void)
              && cfun->machine->frame.reg_offset[LR_REGNUM] >= 0));
 }
 
+/* Return TRUE if Branch Target Identification Mechanism is enabled.  */
+bool
+aarch64_bti_enabled (void)
+{
+  return (aarch64_enable_bti == 1);
+}
+
 /* Emit code to save the callee-saved registers from register number START
    to LIMIT to the stack at the location starting at offset START_OFFSET,
    skipping any write-back candidates if SKIP_WB is true.  */

diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index 69a5103a082f2fb32777e6aae21049d4ec30891e..6de7b225f22d99e16fa7fb43fe7fbce6257f9043 100644 (file)
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -33,6 +33,9 @@ const char *x_aarch64_override_tune_string
 TargetVariable
 unsigned long aarch64_isa_flags = 0
 
+TargetVariable
+unsigned aarch64_enable_bti = 2
+
 ; The TLS dialect names to use with -mtls-dialect.
 
 Enum

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index c7c80f73012d0691df16fcea1605550f7e7b6fe8..56649bfd45a75a6346b28dbd303ab4f31ad89e55 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -15757,6 +15757,7 @@ level: signing functions that save the return address to memory (non-leaf
 functions will practically always do this) using the a-key.  The optional
 argument @samp{leaf} can be used to extend the signing to include leaf
 functions.
+@samp{bti} turns on branch target identification mechanism.
 
 @item -msve-vector-bits=@var{bits}
 @opindex msve-vector-bits