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[PATCH v6] aarch64: Add split-stack support
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 7 Feb 2018 16:07:11 -0200
- Subject: [PATCH v6] aarch64: Add split-stack support
- Authentication-results: sourceware.org; auth=none
Changes from previous version:
- Changed the wait to call __morestack to use use a branch with link
instead of a simple branch. This allows use a call instruction and
avoid possible issues with later optimization passes which might
see a branch outside the instruction block (as noticed in previous
iterations while building a more complex workload as speccpu2006).
- Change the return address to use the branch with link value and
set x12 to save x30. This simplifies the required instructions
to setup/save the return address.
--
This patch adds the split-stack support on aarch64 (PR #67877). As for
other ports this patch should be used along with glibc and gold support.
The support is done similar to other architectures: a split-stack field
is allocated before TCB by glibc, a target-specific __morestack implementation
and helper functions are added in libgcc and compiler supported in adjusted
(split-stack prologue, va_start for argument handling). I also plan to
send the gold support to adjust stack allocation acrosss split-stack
and default code calls.
Current approach is to set the final stack adjustments using a 2 instructions
at most (mov/movk) which limits stack allocation to upper limit of 4GB.
The morestack call is non standard with x10 hollding the requested stack
pointer, x11 the argument pointer (if required), and x12 to return
continuation address. Unwinding is handled by a personality routine that
knows how to find stack segments.
Split-stack prologue on function entry is as follow (this goes before the
usual function prologue):
function:
mrs x9, tpidr_el0
ldur x9, [x9, -8]
mov x10, <required stack allocation>
movk x10, #0x0, lsl #16
sub x10, sp, x10
mov x11, sp # if function has stacked arguments
cmp x9, x10
bcc .LX
main_fn_entry:
[function prologue]
LX:
bl __morestack
b main_fn_entry
Notes:
1. Even if a function does not allocate a stack frame, a split-stack prologue
is created. It is to avoid issues with tail call for external symbols
which might require linker adjustment (libgo/runtime/go-varargs.c).
2. Basic-block reordering (enabled with -O2) will move split-stack TCB ldur
to after the required stack calculation.
3. Similar to powerpc, When the linker detects a call from split-stack to
non-split-stack code, it adds 16k (or more) to the value found in "allocate"
instructions (so non-split-stack code gets a larger stack). The amount is
tunable by a linker option. This feature is only implemented in the GNU
gold linker.
4. AArch64 does not handle >4G stack initially and although it is possible
to implement it, limiting to 4G allows to materize the allocation with
only 2 instructions (mov + movk) and thus simplifying the linker
adjustments required. Supporting multiple threads each requiring more
than 4G of stack is probably not that important, and likely to OOM at
run time.
5. The TCB support on GLIBC is meant to be included in version 2.28.
6. Besides a regression tests I also checked with a SPECcpu2006 run with
-fsplit-stack additional option. I saw no regression besides 416.gamess
which fails on trunk as well (not sure if some misconfiguration in my
environment).
libgcc/ChangeLog:
* libgcc/config.host: Use t-stack and t-statck-aarch64 for
aarch64*-*-linux.
* libgcc/config/aarch64/morestack-c.c: New file.
* libgcc/config/aarch64/morestack.S: Likewise.
* libgcc/config/aarch64/t-stack-aarch64: Likewise.
* libgcc/generic-morestack.c (__splitstack_find): Add aarch64-specific
code.
gcc/ChangeLog:
* common/config/aarch64/aarch64-common.c
(aarch64_supports_split_stack): New function.
(TARGET_SUPPORTS_SPLIT_STACK): New macro.
* gcc/config/aarch64/aarch64-linux.h (TARGET_ASM_FILE_END): Remove
macro.
* gcc/config/aarch64/aarch64-protos.h: Add
aarch64_expand_split_stack_prologue and
aarch64_split_stack_space_check.
* gcc/config/aarch64/aarch64.c (aarch64_expand_builtin_va_start): Use
internal argument pointer instead of virtual_incoming_args_rtx.
(morestack_ref): New symbol.
(aarch64_load_split_stack_value): New function.
(aarch64_expand_split_stack_prologue): Likewise.
(aarch64_internal_arg_pointer): Likewise.
(aarch64_file_end): Emit the split-stack note sections.
(aarch64_split_stack_space_check): Likewise.
(TARGET_ASM_FILE_END): New macro.
(TARGET_INTERNAL_ARG_POINTER): Likewise.
* gcc/config/aarch64/aarch64.h (aarch64_frame): Add
split_stack_arg_pointer to setup the argument pointer when using
split-stack.
* gcc/config/aarch64/aarch64.md
(UNSPECV_STACK_CHECK): New define.
(split_stack_prologue): New expand.
(split_stack_space_check): Likewise.
---
gcc/common/config/aarch64/aarch64-common.c | 28 +++-
gcc/config/aarch64/aarch64-linux.h | 2 -
gcc/config/aarch64/aarch64-protos.h | 2 +
gcc/config/aarch64/aarch64.c | 182 ++++++++++++++++++++-
gcc/config/aarch64/aarch64.h | 3 +
gcc/config/aarch64/aarch64.md | 29 ++++
libgcc/config.host | 1 +
libgcc/config/aarch64/morestack-c.c | 87 ++++++++++
libgcc/config/aarch64/morestack.S | 254 +++++++++++++++++++++++++++++
libgcc/config/aarch64/t-stack-aarch64 | 3 +
libgcc/generic-morestack.c | 1 +
11 files changed, 588 insertions(+), 4 deletions(-)
create mode 100644 libgcc/config/aarch64/morestack-c.c
create mode 100644 libgcc/config/aarch64/morestack.S
create mode 100644 libgcc/config/aarch64/t-stack-aarch64
diff --git a/gcc/common/config/aarch64/aarch64-common.c b/gcc/common/config/aarch64/aarch64-common.c
index 71d3953..cf17e2f 100644
--- a/gcc/common/config/aarch64/aarch64-common.c
+++ b/gcc/common/config/aarch64/aarch64-common.c
@@ -107,6 +107,33 @@ aarch64_handle_option (struct gcc_options *opts,
}
}
+/* -fsplit-stack uses a TCB field available on glibc-2.27. GLIBC also
+ exports symbol, __tcb_private_ss, to signal it has the field available
+ on TCB bloc. This aims to prevent binaries linked against newer
+ GLIBC to run on non-supported ones. */
+
+static bool
+aarch64_supports_split_stack (bool report ATTRIBUTE_UNUSED,
+ struct gcc_options *opts ATTRIBUTE_UNUSED)
+{
+#ifndef TARGET_GLIBC_MAJOR
+#define TARGET_GLIBC_MAJOR 0
+#endif
+#ifndef TARGET_GLIBC_MINOR
+#define TARGET_GLIBC_MINOR 0
+#endif
+ /* Note: Can't test DEFAULT_ABI here, it isn't set until later. */
+ if (TARGET_GLIBC_MAJOR * 1000 + TARGET_GLIBC_MINOR >= 2026)
+ return true;
+
+ if (report)
+ error ("%<-fsplit-stack%> currently only supported on AArch64 GNU/Linux with glibc-2.27 or later");
+ return false;
+}
+
+#undef TARGET_SUPPORTS_SPLIT_STACK
+#define TARGET_SUPPORTS_SPLIT_STACK aarch64_supports_split_stack
+
struct gcc_targetm_common targetm_common = TARGETM_COMMON_INITIALIZER;
/* An ISA extension in the co-processor and main instruction set space. */
@@ -340,4 +367,3 @@ aarch64_rewrite_mcpu (int argc, const char **argv)
}
#undef AARCH64_CPU_NAME_LENGTH
-
diff --git a/gcc/config/aarch64/aarch64-linux.h b/gcc/config/aarch64/aarch64-linux.h
index bf1327e..1189bfe 100644
--- a/gcc/config/aarch64/aarch64-linux.h
+++ b/gcc/config/aarch64/aarch64-linux.h
@@ -81,8 +81,6 @@
} \
while (0)
-#define TARGET_ASM_FILE_END file_end_indicate_exec_stack
-
/* Uninitialized common symbols in non-PIE executables, even with
strong definitions in dependent shared libraries, will resolve
to COPY relocated symbol in the executable. See PR65780. */
diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index cda2895..20fe10e 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -450,6 +450,8 @@ void aarch64_expand_sve_mem_move (rtx, rtx, machine_mode);
bool aarch64_maybe_expand_sve_subreg_move (rtx, rtx);
void aarch64_split_sve_subreg_move (rtx, rtx, rtx);
void aarch64_expand_prologue (void);
+void aarch64_expand_split_stack_prologue (void);
+void aarch64_split_stack_space_check (rtx, rtx);
void aarch64_expand_vector_init (rtx, rtx);
void aarch64_init_cumulative_args (CUMULATIVE_ARGS *, const_tree, rtx,
const_tree, unsigned);
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 7c9c6e5..c653755 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -71,6 +71,7 @@
#include "selftest.h"
#include "selftest-rtl.h"
#include "rtx-vector-builder.h"
+#include "except.h"
/* This file should be included last. */
#include "target-def.h"
@@ -12073,7 +12074,7 @@ aarch64_expand_builtin_va_start (tree valist, rtx nextarg ATTRIBUTE_UNUSED)
/* Emit code to initialize STACK, which points to the next varargs stack
argument. CUM->AAPCS_STACK_SIZE gives the number of stack words used
by named arguments. STACK is 8-byte aligned. */
- t = make_tree (TREE_TYPE (stack), virtual_incoming_args_rtx);
+ t = make_tree (TREE_TYPE (stack), crtl->args.internal_arg_pointer);
if (cum->aapcs_stack_size > 0)
t = fold_build_pointer_plus_hwi (t, cum->aapcs_stack_size * UNITS_PER_WORD);
t = build2 (MODIFY_EXPR, TREE_TYPE (stack), stack, t);
@@ -17351,6 +17352,179 @@ aarch64_select_early_remat_modes (sbitmap modes)
}
}
+/* -fsplit-stack support. */
+
+/* A SYMBOL_REF for __morestack. */
+static GTY(()) rtx morestack_ref;
+
+/* Load split-stack area from thread pointer position. The split-stack is
+ allocate just before thread pointer. */
+
+static rtx
+aarch64_load_split_stack_value (bool use_hard_reg)
+{
+ /* Offset from thread pointer to split-stack area. */
+ const int psso = -8;
+
+ rtx ssvalue = use_hard_reg
+ ? gen_rtx_REG (Pmode, R9_REGNUM) : gen_reg_rtx (Pmode);
+ ssvalue = aarch64_load_tp (ssvalue);
+ rtx mem = gen_rtx_MEM (Pmode, plus_constant (Pmode, ssvalue, psso));
+ emit_move_insn (ssvalue, mem);
+ return ssvalue;
+}
+
+/* Emit -fsplit-stack prologue, which goes before the regular function
+ prologue. */
+
+void
+aarch64_expand_split_stack_prologue (void)
+{
+ rtx ssvalue, reg10, reg11, reg12, cc, jump;
+ HOST_WIDE_INT allocate;
+ rtx_code_label *ok_label;
+ rtx_insn *insn;
+
+ gcc_assert (flag_split_stack && reload_completed);
+
+ /* It limits total maximum stack allocation on 4G so its value can be
+ materialized using two instructions at most (movn/movk). It might be
+ used by the linker to add some extra space for split calling non split
+ stack functions. */
+ allocate = constant_lower_bound (cfun->machine->frame.frame_size);
+ if (allocate > ((int64_t)1 << 32))
+ {
+ sorry ("Stack frame larger than 4G is not supported for -fsplit-stack");
+ return;
+ }
+
+ if (morestack_ref == NULL_RTX)
+ {
+ morestack_ref = gen_rtx_SYMBOL_REF (Pmode, "__morestack");
+ SYMBOL_REF_FLAGS (morestack_ref) |= (SYMBOL_FLAG_LOCAL
+ | SYMBOL_FLAG_FUNCTION);
+ }
+
+ ssvalue = aarch64_load_split_stack_value (true);
+
+ /* Always emit two insns to calculate the requested stack, so the linker
+ can edit them when adjusting size for calling non-split-stack code. */
+ reg10 = gen_rtx_REG (Pmode, R10_REGNUM);
+ emit_insn (gen_rtx_SET (reg10, GEN_INT (allocate & 0xffff)));
+ emit_insn (gen_insv_immdi (reg10, GEN_INT (16),
+ GEN_INT ((allocate & 0xffff0000) >> 16)));
+ emit_insn (gen_sub3_insn (reg10, stack_pointer_rtx, reg10));
+
+ ok_label = gen_label_rtx ();
+
+ /* If function uses stacked arguments save the old stack value so morestack
+ can return it. */
+ reg11 = gen_rtx_REG (Pmode, R11_REGNUM);
+ if (maybe_gt(crtl->args.size, 0)
+ || maybe_gt(cfun->machine->frame.saved_varargs_size, 0))
+ emit_move_insn (reg11, stack_pointer_rtx);
+
+ /* x12 holds the function entry x30 which will be restored by morestack. */
+ reg12 = gen_rtx_REG (Pmode, R12_REGNUM);
+ emit_move_insn (reg12, gen_rtx_REG (Pmode, R30_REGNUM));
+
+ ok_label = gen_label_rtx ();
+ cc = aarch64_gen_compare_reg (GEU, reg10, ssvalue);
+ jump = gen_rtx_IF_THEN_ELSE (VOIDmode,
+ gen_rtx_fmt_ee (GEU, VOIDmode, cc, const0_rtx),
+ gen_rtx_LABEL_REF (VOIDmode, ok_label),
+ pc_rtx);
+ insn = emit_jump_insn (gen_rtx_SET (pc_rtx, jump));
+ JUMP_LABEL (insn) = ok_label;
+ /* Mark the jump as very likely to be taken. */
+ add_reg_br_prob_note (insn, profile_probability::very_likely ());
+
+ insn = emit_call_insn (gen_call (gen_rtx_MEM (Pmode, morestack_ref),
+ const0_rtx, const0_rtx));
+
+ rtx call_fusage = NULL_RTX;
+ use_reg (&call_fusage, reg10);
+ use_reg (&call_fusage, reg11);
+ use_reg (&call_fusage, reg12);
+ add_function_usage_to (insn, call_fusage);
+ /* Indicate that this function can't jump to non-local gotos. */
+ make_reg_eh_region_note_nothrow_nononlocal (insn);
+
+ emit_label (ok_label);
+ LABEL_NUSES (ok_label)++;
+}
+
+/* Implement TARGET_ASM_FILE_END. */
+
+static void
+aarch64_file_end (void)
+{
+ file_end_indicate_exec_stack ();
+
+ if (flag_split_stack)
+ {
+ file_end_indicate_split_stack ();
+
+ switch_to_section (data_section);
+ fprintf (asm_out_file, "\t.align 3\n");
+ fprintf (asm_out_file, "\t.quad __libc_tcb_private_ss\n");
+ }
+}
+
+/* Return the internal arg pointer used for function incoming arguments. */
+
+static rtx
+aarch64_internal_arg_pointer (void)
+{
+ if (flag_split_stack
+ && (lookup_attribute ("no_split_stack", DECL_ATTRIBUTES (cfun->decl))
+ == NULL))
+ {
+ if (cfun->machine->frame.split_stack_arg_pointer == NULL_RTX)
+ {
+ rtx pat;
+
+ cfun->machine->frame.split_stack_arg_pointer = gen_reg_rtx (Pmode);
+ REG_POINTER (cfun->machine->frame.split_stack_arg_pointer) = 1;
+
+ /* Put the pseudo initialization right after the note at the
+ beginning of the function. */
+ pat = gen_rtx_SET (cfun->machine->frame.split_stack_arg_pointer,
+ gen_rtx_REG (Pmode, R11_REGNUM));
+ push_topmost_sequence ();
+ emit_insn_after (pat, get_insns ());
+ pop_topmost_sequence ();
+ }
+ return plus_constant (Pmode, cfun->machine->frame.split_stack_arg_pointer,
+ FIRST_PARM_OFFSET (current_function_decl));
+ }
+ return virtual_incoming_args_rtx;
+}
+
+/* Emit -fsplit-stack dynamic stack allocation space check. */
+
+void
+aarch64_split_stack_space_check (rtx size, rtx label)
+{
+ rtx ssvalue, cc, cmp, jump, temp;
+ rtx requested = gen_reg_rtx (Pmode);
+
+ /* Load __private_ss from TCB. */
+ ssvalue = aarch64_load_split_stack_value (false);
+
+ temp = gen_reg_rtx (Pmode);
+
+ /* And compare it with frame pointer plus required stack. */
+ size = force_reg (Pmode, size);
+ emit_move_insn (requested, gen_rtx_MINUS (Pmode, stack_pointer_rtx, size));
+
+ /* Jump to label call if current ss guard is not suffice. */
+ cc = aarch64_gen_compare_reg (GE, temp, ssvalue);
+ cmp = gen_rtx_fmt_ee (GEU, VOIDmode, cc, const0_rtx);
+ jump = emit_jump_insn (gen_condjump (cmp, cc, label));
+ JUMP_LABEL (jump) = label;
+}
+
/* Target-specific selftests. */
#if CHECKING_P
@@ -17423,6 +17597,9 @@ aarch64_run_selftests (void)
#undef TARGET_ASM_FILE_START
#define TARGET_ASM_FILE_START aarch64_start_file
+#undef TARGET_ASM_FILE_END
+#define TARGET_ASM_FILE_END aarch64_file_end
+
#undef TARGET_ASM_OUTPUT_MI_THUNK
#define TARGET_ASM_OUTPUT_MI_THUNK aarch64_output_mi_thunk
@@ -17513,6 +17690,9 @@ aarch64_run_selftests (void)
#undef TARGET_FUNCTION_VALUE_REGNO_P
#define TARGET_FUNCTION_VALUE_REGNO_P aarch64_function_value_regno_p
+#undef TARGET_INTERNAL_ARG_POINTER
+#define TARGET_INTERNAL_ARG_POINTER aarch64_internal_arg_pointer
+
#undef TARGET_GIMPLE_FOLD_BUILTIN
#define TARGET_GIMPLE_FOLD_BUILTIN aarch64_gimple_fold_builtin
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index e3c52f6..20ef441 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -675,6 +675,9 @@ struct GTY (()) aarch64_frame
unsigned wb_candidate2;
bool laid_out;
+
+ /* Alternative internal arg pointer for -fsplit-stack. */
+ rtx split_stack_arg_pointer;
};
typedef struct GTY (()) machine_function
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 5a2a930..3104ed4 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -169,6 +169,7 @@
UNSPEC_CLASTB
UNSPEC_FADDA
UNSPEC_REV_SUBREG
+ UNSPEC_STACK_CHECK
])
(define_c_enum "unspecv" [
@@ -6010,6 +6011,34 @@
(match_operand 1))
(clobber (reg:CC CC_REGNUM))])])
+;; Handle -fsplit-stack
+(define_expand "split_stack_prologue"
+ [(const_int 0)]
+ ""
+{
+ aarch64_expand_split_stack_prologue ();
+ DONE;
+})
+
+;; If there are operand 0 bytes available on the stack, jump to
+;; operand 1.
+(define_expand "split_stack_space_check"
+ [(set (match_dup 2)
+ (unspec [(const_int 0)] UNSPEC_STACK_CHECK))
+ (set (match_dup 3)
+ (minus (reg SP_REGNUM)
+ (match_operand 0)))
+ (set (match_dup 4) (compare:CC (match_dup 3) (match_dup 2)))
+ (set (pc) (if_then_else
+ (geu (match_dup 4) (const_int 0))
+ (label_ref (match_operand 1))
+ (pc)))]
+ ""
+{
+ aarch64_split_stack_space_check (operands[0], operands[1]);
+ DONE;
+})
+
;; AdvSIMD Stuff
(include "aarch64-simd.md")
diff --git a/libgcc/config.host b/libgcc/config.host
index 96d55a4..d6a2d15 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -355,6 +355,7 @@ aarch64*-*-linux*)
md_unwind_header=aarch64/linux-unwind.h
tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
+ tmake_file="${tmake_file} t-stack aarch64/t-stack-aarch64"
;;
alpha*-*-linux*)
tmake_file="${tmake_file} alpha/t-alpha alpha/t-ieee t-crtfm alpha/t-linux"
diff --git a/libgcc/config/aarch64/morestack-c.c b/libgcc/config/aarch64/morestack-c.c
new file mode 100644
index 0000000..8de531f
--- /dev/null
+++ b/libgcc/config/aarch64/morestack-c.c
@@ -0,0 +1,87 @@
+/* AArch64 support for -fsplit-stack.
+ * Copyright (C) 2018 Free Software Foundation, Inc.
+ *
+ * This file is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 3, or (at your option) any
+ * later version.
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * Under Section 7 of GPL version 3, you are granted additional
+ * permissions described in the GCC Runtime Library Exception, version
+ * 3.1, as published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License and
+ * a copy of the GCC Runtime Library Exception along with this program;
+ * see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef inhibit_libc
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include "generic-morestack.h"
+
+#define INITIAL_STACK_SIZE 0x4000
+#define BACKOFF 0x1000
+
+void __generic_morestack_set_initial_sp (void *sp, size_t len);
+void *__morestack_get_guard (void);
+void __morestack_set_guard (void *);
+void *__morestack_make_guard (void *stack, size_t size);
+void __morestack_load_mmap (void);
+
+/* split-stack area position from thread pointer. */
+static inline void *
+ss_pointer (void)
+{
+#define SS_OFFSET (-8)
+ return (void*) ((uintptr_t) __builtin_thread_pointer() + SS_OFFSET);
+}
+
+/* Initialize the stack guard when the program starts or when a new
+ thread. This is called from a constructor using ctors section. */
+void
+__stack_split_initialize (void)
+{
+ register uintptr_t* sp __asm__ ("sp");
+ uintptr_t *ss = ss_pointer ();
+ *ss = (uintptr_t)sp - INITIAL_STACK_SIZE;
+ __generic_morestack_set_initial_sp (sp, INITIAL_STACK_SIZE);
+}
+
+/* Return current __private_ss. */
+void *
+__morestack_get_guard (void)
+{
+ void **ss = ss_pointer ();
+ return *ss;
+}
+
+/* Set __private_ss to ptr. */
+void
+__morestack_set_guard (void *ptr)
+{
+ void **ss = ss_pointer ();
+ *ss = ptr;
+}
+
+/* Return the stack guard value for given stack. */
+void *
+__morestack_make_guard (void *stack, size_t size)
+{
+ return (void*)((uintptr_t) stack - size + BACKOFF);
+}
+
+/* Make __stack_split_initialize a high priority constructor. */
+static void (*const ctors [])
+ __attribute__ ((used, section (".ctors.65535"), aligned (sizeof (void *))))
+ = { __stack_split_initialize, __morestack_load_mmap };
+
+#endif /* !defined (inhibit_libc) */
diff --git a/libgcc/config/aarch64/morestack.S b/libgcc/config/aarch64/morestack.S
new file mode 100644
index 0000000..59a6391
--- /dev/null
+++ b/libgcc/config/aarch64/morestack.S
@@ -0,0 +1,254 @@
+# AArch64 support for -fsplit-stack.
+# Copyright (C) 2018 Free Software Foundation, Inc.
+
+# This file is part of GCC.
+
+# GCC is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation; either version 3, or (at your option) any later
+# version.
+
+# GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+# for more details.
+
+# Under Section 7 of GPL version 3, you are granted additional
+# permissions described in the GCC Runtime Library Exception, version
+# 3.1, as published by the Free Software Foundation.
+
+# You should have received a copy of the GNU General Public License and
+# a copy of the GCC Runtime Library Exception along with this program;
+# see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+# <http://www.gnu.org/licenses/>.
+
+/* Define an entry point visible from C. */
+#define ENTRY(name) \
+ .globl name; \
+ .type name,%function; \
+ .align 4; \
+ name##:
+
+#define END(name) \
+ .size name,.-name
+
+/* __morestack frame size. */
+#define MORESTACK_FRAMESIZE 112
+/* Offset from __morestack frame where the new stack size is saved and
+ passed to __generic_morestack. */
+#define NEWSTACK_SAVE 96
+
+# Excess space needed to call ld.so resolver for lazy plt resolution.
+# Go uses sigaltstack so this doesn't need to also cover signal frame size.
+#define BACKOFF 0x1000
+# Large excess allocated when calling non-split-stack code.
+#define NON_SPLIT_STACK 0x100000
+
+/* split-stack area position from thread pointer. */
+#define SPLITSTACK_PTR_TP -8
+
+ .text
+ENTRY(__morestack_non_split)
+ .cfi_startproc
+# We use a cleanup to restore the TCB split stack field if an exception is
+# through this code.
+ sub x10, x10, NON_SPLIT_STACK
+ .cfi_endproc
+END(__morestack_non_split)
+# Fall through into __morestack
+
+# This function is called with non-standard calling convention: on entry
+# x10 is the requested stack pointer, x11 is previous stack pointer (if
+# functions has stacked arguments which needs to be restored), and x12 is
+# the caller link register on function entry (which will be restored by
+# morestack when returning to caller). The split-stack prologue is in
+# the form:
+#
+# function:
+# mrs x9, tpidr_el0
+# ldur x9, [x9, #-8]
+# mov x10, <required stack allocation>
+# movk x10, #0x0, lsl #16
+# sub x10, sp, x10
+# mov x11, sp # if function has stacked arguments
+# mov x12, x30
+# cmp x9, x10
+# bcc .LX
+# main_fn_entry:
+# [function body]
+# LX:
+# bl __morestack
+# b main_fn_entry
+#
+# The N bit is also restored to indicate that the function is called
+# (so the prologue addition can set up the argument pointer correctly).
+
+ENTRY(__morestack)
+.LFB1:
+ .cfi_startproc
+
+#ifdef __PIC__
+ .cfi_personality 0x9b,DW.ref.__gcc_personality_v0
+ .cfi_lsda 0x1b,.LLSDA1
+#else
+ .cfi_personality 0x3,__gcc_personality_v0
+ .cfi_lsda 0x3,.LLSDA1
+#endif
+ # Calculate requested stack size.
+ sub x10, sp, x10
+
+ # Save parameters
+ stp x29, x12, [sp, -MORESTACK_FRAMESIZE]!
+ .cfi_def_cfa_offset MORESTACK_FRAMESIZE
+ .cfi_offset 29, -MORESTACK_FRAMESIZE
+ .cfi_offset 30, -MORESTACK_FRAMESIZE+8
+ add x29, sp, 0
+ .cfi_def_cfa_register 29
+ # Adjust the requested stack size for the frame pointer save.
+ stp x0, x1, [x29, 16]
+ stp x2, x3, [x29, 32]
+ add x10, x10, BACKOFF
+ stp x4, x5, [x29, 48]
+ stp x6, x7, [x29, 64]
+ stp x8, x30, [x29, 80]
+ str x10, [x29, 96]
+
+ # void __morestack_block_signals (void)
+ bl __morestack_block_signals
+
+ # void *__generic_morestack (size_t *pframe_size,
+ # void *old_stack,
+ # size_t param_size)
+ # pframe_size: is the size of the required stack frame (the function
+ # amount of space remaining on the allocated stack).
+ # old_stack: points at the parameters the old stack
+ # param_size: size in bytes of parameters to copy to the new stack.
+ add x0, x29, NEWSTACK_SAVE
+ add x1, x29, MORESTACK_FRAMESIZE
+ mov x2, 0
+ bl __generic_morestack
+
+ # Start using new stack
+ mov sp, x0
+
+ # Set __private_ss stack guard for the new stack.
+ ldr x9, [x29, NEWSTACK_SAVE]
+ add x0, x0, BACKOFF
+ sub x0, x0, x9
+.LEHB0:
+ mrs x1, tpidr_el0
+ str x0, [x1, SPLITSTACK_PTR_TP]
+
+ # void __morestack_unblock_signals (void)
+ bl __morestack_unblock_signals
+
+ # Set up for a call to the target function.
+ ldp x0, x1, [x29, 16]
+ ldp x2, x3, [x29, 32]
+ ldp x4, x5, [x29, 48]
+ ldp x6, x7, [x29, 64]
+ ldp x8, x12, [x29, 80]
+ add x11, x29, MORESTACK_FRAMESIZE
+ ldr x30, [x29, 8]
+ # Indicate __morestack was called.
+ cmp x12, 0
+ blr x12
+
+ stp x0, x1, [x29, 16]
+ stp x2, x3, [x29, 32]
+ stp x4, x5, [x29, 48]
+ stp x6, x7, [x29, 64]
+
+ bl __morestack_block_signals
+
+ # void *__generic_releasestack (size_t *pavailable)
+ add x0, x29, NEWSTACK_SAVE
+ bl __generic_releasestack
+
+ # Reset __private_ss stack guard to value for old stack
+ ldr x9, [x29, NEWSTACK_SAVE]
+ add x0, x0, BACKOFF
+ sub x0, x0, x9
+
+ # Update TCB split stack field
+.LEHE0:
+ mrs x1, tpidr_el0
+ str x0, [x1, SPLITSTACK_PTR_TP]
+
+ bl __morestack_unblock_signals
+
+ # Use old stack again.
+ add sp, x29, MORESTACK_FRAMESIZE
+
+ ldp x0, x1, [x29, 16]
+ ldp x2, x3, [x29, 32]
+ ldp x4, x5, [x29, 48]
+ ldp x6, x7, [x29, 64]
+ ldp x29, x30, [x29]
+
+ .cfi_remember_state
+ .cfi_restore 30
+ .cfi_restore 29
+ .cfi_def_cfa 31, 0
+
+ ret
+
+# This is the cleanup code called by the stack unwinder when
+# unwinding through code between .LEHB0 and .LEHE0 above.
+cleanup:
+ .cfi_restore_state
+ # Reuse the new stack allocation to save/restore the
+ # exception header
+ str x0, [x29, NEWSTACK_SAVE]
+ # size_t __generic_findstack (void *stack)
+ add x0, x29, MORESTACK_FRAMESIZE
+ bl __generic_findstack
+ sub x0, x29, x0
+ add x0, x0, BACKOFF
+ # Restore split-stack guard value
+ mrs x1, tpidr_el0
+ str x0, [x1, SPLITSTACK_PTR_TP]
+ ldr x0, [x29, NEWSTACK_SAVE]
+ b _Unwind_Resume
+ .cfi_endproc
+END(__morestack)
+
+ .section .gcc_except_table,"a",@progbits
+ .align 4
+.LLSDA1:
+ # @LPStart format (omit)
+ .byte 0xff
+ # @TType format (omit)
+ .byte 0xff
+ # Call-site format (uleb128)
+ .byte 0x1
+ # Call-site table length
+ .uleb128 .LLSDACSE1-.LLSDACSB1
+.LLSDACSB1:
+ # region 0 start
+ .uleb128 .LEHB0-.LFB1
+ # length
+ .uleb128 .LEHE0-.LEHB0
+ # landing pad
+ .uleb128 cleanup-.LFB1
+ # no action (ie a cleanup)
+ .uleb128 0
+.LLSDACSE1:
+
+
+ .global __gcc_personality_v0
+#ifdef __PIC__
+ # Build a position independent reference to the personality function.
+ .hidden DW.ref.__gcc_personality_v0
+ .weak DW.ref.__gcc_personality_v0
+ .section .data.DW.ref.__gcc_personality_v0,"awG",@progbits,DW.ref.__gcc_personality_v0,comdat
+ .type DW.ref.__gcc_personality_v0, @object
+ .align 3
+DW.ref.__gcc_personality_v0:
+ .size DW.ref.__gcc_personality_v0, 8
+ .quad __gcc_personality_v0
+#endif
+
+ .section .note.GNU-stack,"",@progbits
+ .section .note.GNU-split-stack,"",@progbits
+ .section .note.GNU-no-split-stack,"",@progbits
diff --git a/libgcc/config/aarch64/t-stack-aarch64 b/libgcc/config/aarch64/t-stack-aarch64
new file mode 100644
index 0000000..4babb4e
--- /dev/null
+++ b/libgcc/config/aarch64/t-stack-aarch64
@@ -0,0 +1,3 @@
+# Makefile fragment to support -fsplit-stack for aarch64.
+LIB2ADD_ST += $(srcdir)/config/aarch64/morestack.S \
+ $(srcdir)/config/aarch64/morestack-c.c
diff --git a/libgcc/generic-morestack.c b/libgcc/generic-morestack.c
index 80bfd7f..574f58d 100644
--- a/libgcc/generic-morestack.c
+++ b/libgcc/generic-morestack.c
@@ -943,6 +943,7 @@ __splitstack_find (void *segment_arg, void *sp, size_t *len,
nsp -= 2 * 160;
#elif defined __s390__
nsp -= 2 * 96;
+#elif defined __aarch64__
#else
#error "unrecognized target"
#endif
--
2.7.4