Merge tag 'pr-arm32-ti-in-task' of git://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux into devel-stable

ARM: support THREAD_INFO_IN_TASK

Move thread_info off the stack and into the task struct, as is done by
many other architectures. This requires a method to find the task struct
of the task currently running on the CPU, which is provided in this case
by the user space TLS (Thread Local Storage) register. This implies that
the feature is only supported on CPUs that implement this register,
i.e., ARM v6k or later.

Kindly tested by Amit and reviewed by Linus. The first patch is against
the GCC plugins subsystem, but was reviewed by the maintainer and can be
taken through the ARM tree.

1 files changed, 6 insertions, 21 deletions

diff --git a/scripts/gcc-plugins/arm_ssp_per_task_plugin.c b/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
index 8c1af9bdcb1b..7328d037f975 100644
--- a/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
+++ b/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
@@ -4,7 +4,7 @@
 
 __visible int plugin_is_GPL_compatible;
 
-static unsigned int sp_mask, canary_offset;
+static unsigned int canary_offset;
 
 static unsigned int arm_pertask_ssp_rtl_execute(void)
 {
@@ -13,7 +13,7 @@ static unsigned int arm_pertask_ssp_rtl_execute(void)
 	for (insn = get_insns(); insn; insn = NEXT_INSN(insn)) {
 		const char *sym;
 		rtx body;
-		rtx mask, masked_sp;
+		rtx current;
 
 		/*
 		 * Find a SET insn involving a SYMBOL_REF to __stack_chk_guard
@@ -30,19 +30,13 @@ static unsigned int arm_pertask_ssp_rtl_execute(void)
 
 		/*
 		 * Replace the source of the SET insn with an expression that
-		 * produces the address of the copy of the stack canary value
-		 * stored in struct thread_info
+		 * produces the address of the current task's stack canary value
 		 */
-		mask = GEN_INT(sext_hwi(sp_mask, GET_MODE_PRECISION(Pmode)));
-		masked_sp = gen_reg_rtx(Pmode);
+		current = gen_reg_rtx(Pmode);
 
-		emit_insn_before(gen_rtx_set(masked_sp,
-					     gen_rtx_AND(Pmode,
-							 stack_pointer_rtx,
-							 mask)),
-				 insn);
+		emit_insn_before(gen_load_tp_hard(current), insn);
 
-		SET_SRC(body) = gen_rtx_PLUS(Pmode, masked_sp,
+		SET_SRC(body) = gen_rtx_PLUS(Pmode, current,
 					     GEN_INT(canary_offset));
 	}
 	return 0;
@@ -72,7 +66,6 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
 	const char * const plugin_name = plugin_info->base_name;
 	const int argc = plugin_info->argc;
 	const struct plugin_argument *argv = plugin_info->argv;
-	int tso = 0;
 	int i;
 
 	if (!plugin_default_version_check(version, &gcc_version)) {
@@ -91,11 +84,6 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
 			return 1;
 		}
 
-		if (!strcmp(argv[i].key, "tso")) {
-			tso = atoi(argv[i].value);
-			continue;
-		}
-
 		if (!strcmp(argv[i].key, "offset")) {
 			canary_offset = atoi(argv[i].value);
 			continue;
@@ -105,9 +93,6 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
 		return 1;
 	}
 
-	/* create the mask that produces the base of the stack */
-	sp_mask = ~((1U << (12 + tso)) - 1);
-
 	PASS_INFO(arm_pertask_ssp_rtl, "expand", 1, PASS_POS_INSERT_AFTER);
 
 	register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP,