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| | 'Retpoline' mitigation technique for Spectre (branch target injection)
[CVE-2017-5715]:
https://security.googleblog.com/2018/01/more-details-about-mitigations-for-cpu_4.html
https://support.google.com/faqs/answer/7625886
https://spectreattack.com/
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715
Patch copied from the 'retpoline-regnames' branch of upstream source repository
(please keep an eye for new branches or updates for existing branches):
http://git.infradead.org/users/dwmw2/gcc-retpoline.git
From f23f45109139911714e2164191c0228500ebef92 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 6 Nov 2017 09:11:08 -0800
Subject: [PATCH 01/10] i386: Move struct ix86_frame to machine_function
Make ix86_frame available to i386 code generation. This is needed to
backport the patch set of -mindirect-branch= to mitigate variant #2 of
the speculative execution vulnerabilities on x86 processors identified
by CVE-2017-5715, aka Spectre.
Backport from mainline
* config/i386/i386.c (ix86_frame): Moved to ...
* config/i386/i386.h (ix86_frame): Here.
(machine_function): Add frame.
* config/i386/i386.c (ix86_compute_frame_layout): Repace the
frame argument with &cfun->machine->frame.
(ix86_can_use_return_insn_p): Don't pass &frame to
ix86_compute_frame_layout. Copy frame from cfun->machine->frame.
(ix86_can_eliminate): Likewise.
(ix86_expand_prologue): Likewise.
(ix86_expand_epilogue): Likewise.
(ix86_expand_split_stack_prologue): Likewise.
---
gcc/config/i386/i386.c | 68 ++++++++++----------------------------------------
gcc/config/i386/i386.h | 53 ++++++++++++++++++++++++++++++++++++++-
2 files changed, 65 insertions(+), 56 deletions(-)
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 8a3782c0298..813337242d8 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -2444,53 +2444,6 @@ struct GTY(()) stack_local_entry {
struct stack_local_entry *next;
};
-/* Structure describing stack frame layout.
- Stack grows downward:
-
- [arguments]
- <- ARG_POINTER
- saved pc
-
- saved static chain if ix86_static_chain_on_stack
-
- saved frame pointer if frame_pointer_needed
- <- HARD_FRAME_POINTER
- [saved regs]
- <- regs_save_offset
- [padding0]
-
- [saved SSE regs]
- <- sse_regs_save_offset
- [padding1] |
- | <- FRAME_POINTER
- [va_arg registers] |
- |
- [frame] |
- |
- [padding2] | = to_allocate
- <- STACK_POINTER
- */
-struct ix86_frame
-{
- int nsseregs;
- int nregs;
- int va_arg_size;
- int red_zone_size;
- int outgoing_arguments_size;
-
- /* The offsets relative to ARG_POINTER. */
- HOST_WIDE_INT frame_pointer_offset;
- HOST_WIDE_INT hard_frame_pointer_offset;
- HOST_WIDE_INT stack_pointer_offset;
- HOST_WIDE_INT hfp_save_offset;
- HOST_WIDE_INT reg_save_offset;
- HOST_WIDE_INT sse_reg_save_offset;
-
- /* When save_regs_using_mov is set, emit prologue using
- move instead of push instructions. */
- bool save_regs_using_mov;
-};
-
/* Which cpu are we scheduling for. */
enum attr_cpu ix86_schedule;
@@ -2582,7 +2535,7 @@ static unsigned int ix86_function_arg_boundary (machine_mode,
const_tree);
static rtx ix86_static_chain (const_tree, bool);
static int ix86_function_regparm (const_tree, const_tree);
-static void ix86_compute_frame_layout (struct ix86_frame *);
+static void ix86_compute_frame_layout (void);
static bool ix86_expand_vector_init_one_nonzero (bool, machine_mode,
rtx, rtx, int);
static void ix86_add_new_builtins (HOST_WIDE_INT, HOST_WIDE_INT);
@@ -11903,7 +11856,8 @@ ix86_can_use_return_insn_p (void)
if (crtl->args.pops_args && crtl->args.size >= 32768)
return 0;
- ix86_compute_frame_layout (&frame);
+ ix86_compute_frame_layout ();
+ frame = cfun->machine->frame;
return (frame.stack_pointer_offset == UNITS_PER_WORD
&& (frame.nregs + frame.nsseregs) == 0);
}
@@ -12389,8 +12343,8 @@ ix86_can_eliminate (const int from, const int to)
HOST_WIDE_INT
ix86_initial_elimination_offset (int from, int to)
{
- struct ix86_frame frame;
- ix86_compute_frame_layout (&frame);
+ ix86_compute_frame_layout ();
+ struct ix86_frame frame = cfun->machine->frame;
if (from == ARG_POINTER_REGNUM && to == HARD_FRAME_POINTER_REGNUM)
return frame.hard_frame_pointer_offset;
@@ -12429,8 +12383,9 @@ ix86_builtin_setjmp_frame_value (void)
/* Fill structure ix86_frame about frame of currently computed function. */
static void
-ix86_compute_frame_layout (struct ix86_frame *frame)
+ix86_compute_frame_layout (void)
{
+ struct ix86_frame *frame = &cfun->machine->frame;
unsigned HOST_WIDE_INT stack_alignment_needed;
HOST_WIDE_INT offset;
unsigned HOST_WIDE_INT preferred_alignment;
@@ -13737,7 +13692,8 @@ ix86_expand_prologue (void)
m->fs.sp_offset = INCOMING_FRAME_SP_OFFSET;
m->fs.sp_valid = true;
- ix86_compute_frame_layout (&frame);
+ ix86_compute_frame_layout ();
+ frame = m->frame;
if (!TARGET_64BIT && ix86_function_ms_hook_prologue (current_function_decl))
{
@@ -14405,7 +14361,8 @@ ix86_expand_epilogue (int style)
bool using_drap;
ix86_finalize_stack_realign_flags ();
- ix86_compute_frame_layout (&frame);
+ ix86_compute_frame_layout ();
+ frame = m->frame;
m->fs.sp_valid = (!frame_pointer_needed
|| (crtl->sp_is_unchanging
@@ -14915,7 +14872,8 @@ ix86_expand_split_stack_prologue (void)
gcc_assert (flag_split_stack && reload_completed);
ix86_finalize_stack_realign_flags ();
- ix86_compute_frame_layout (&frame);
+ ix86_compute_frame_layout ();
+ frame = cfun->machine->frame;
allocate = frame.stack_pointer_offset - INCOMING_FRAME_SP_OFFSET;
/* This is the label we will branch to if we have enough stack
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 9c776dc5172..f9b91286a01 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -2451,9 +2451,56 @@ enum avx_u128_state
\f
#define FASTCALL_PREFIX '@'
\f
+#ifndef USED_FOR_TARGET
+/* Structure describing stack frame layout.
+ Stack grows downward:
+
+ [arguments]
+ <- ARG_POINTER
+ saved pc
+
+ saved static chain if ix86_static_chain_on_stack
+
+ saved frame pointer if frame_pointer_needed
+ <- HARD_FRAME_POINTER
+ [saved regs]
+ <- regs_save_offset
+ [padding0]
+
+ [saved SSE regs]
+ <- sse_regs_save_offset
+ [padding1] |
+ | <- FRAME_POINTER
+ [va_arg registers] |
+ |
+ [frame] |
+ |
+ [padding2] | = to_allocate
+ <- STACK_POINTER
+ */
+struct GTY(()) ix86_frame
+{
+ int nsseregs;
+ int nregs;
+ int va_arg_size;
+ int red_zone_size;
+ int outgoing_arguments_size;
+
+ /* The offsets relative to ARG_POINTER. */
+ HOST_WIDE_INT frame_pointer_offset;
+ HOST_WIDE_INT hard_frame_pointer_offset;
+ HOST_WIDE_INT stack_pointer_offset;
+ HOST_WIDE_INT hfp_save_offset;
+ HOST_WIDE_INT reg_save_offset;
+ HOST_WIDE_INT sse_reg_save_offset;
+
+ /* When save_regs_using_mov is set, emit prologue using
+ move instead of push instructions. */
+ bool save_regs_using_mov;
+};
+
/* Machine specific frame tracking during prologue/epilogue generation. */
-#ifndef USED_FOR_TARGET
struct GTY(()) machine_frame_state
{
/* This pair tracks the currently active CFA as reg+offset. When reg
@@ -2512,6 +2559,9 @@ struct GTY(()) machine_function {
int varargs_fpr_size;
int optimize_mode_switching[MAX_386_ENTITIES];
+ /* Cached initial frame layout for the current function. */
+ struct ix86_frame frame;
+
/* Number of saved registers USE_FAST_PROLOGUE_EPILOGUE
has been computed for. */
int use_fast_prologue_epilogue_nregs;
@@ -2594,6 +2644,7 @@ struct GTY(()) machine_function {
#define ix86_current_function_calls_tls_descriptor \
(ix86_tls_descriptor_calls_expanded_in_cfun && df_regs_ever_live_p (SP_REG))
#define ix86_static_chain_on_stack (cfun->machine->static_chain_on_stack)
+#define ix86_red_zone_size (cfun->machine->frame.red_zone_size)
/* Control behavior of x86_file_start. */
#define X86_FILE_START_VERSION_DIRECTIVE false
--
2.15.1
|