[Skiboot] [PATCH] Add support for new gcc 7 parametrized stack protector
Benjamin Herrenschmidt
benh at kernel.crashing.org
Thu Dec 7 04:38:50 AEDT 2017
This gives us per-cpu guard values as well. For now I just
xor a magic constant with the CPU PIR value.
Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
Makefile.main | 22 ++++++++++++++++++----
asm/head.S | 5 +++++
core/cpu.c | 12 ++++++++++--
core/utils.c | 3 ---
include/cpu.h | 5 +++++
include/stack.h | 2 ++
6 files changed, 40 insertions(+), 9 deletions(-)
diff --git a/Makefile.main b/Makefile.main
index 73c91962..035b72d1 100644
--- a/Makefile.main
+++ b/Makefile.main
@@ -19,6 +19,7 @@ try = $(shell set -e; if ($(1)) >/dev/null 2>&1; \
else echo "$(3)"; fi )
try-cflag = $(call try,$(1) $(2) -x c -c /dev/null -o /dev/null,$(2))
+test_cflag = $(call try,$(1) $(2) -x c -c /dev/null -o /dev/null,1,0)
# Base warnings
CWARNS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
@@ -84,20 +85,33 @@ ifeq ($(SKIBOOT_GCOV),1)
CFLAGS += -fprofile-arcs -ftest-coverage -DSKIBOOT_GCOV=1
endif
+# Check if the new parametrized stack protector option is supported
+# by gcc, otherwise disable stack protector
+STACK_PROT_CFLAGS := -mstack-protector-guard=tls -mstack-protector-guard-reg=r13
+STACK_PROT_CFLAGS += -mstack-protector-guard-offset=0
+HAS_STACK_PROT := $(call test_cflag,$(CC),$(STACK_PROT_CFLAGS))
+
# Stack protector disabled for now. gcc tends to use the TLS to
# access the canary (depending on how gcc was built), and this won't
# work for us.
#
ifeq ($(STACK_CHECK),1)
-#CFLAGS += -fstack-protector-all -pg
-CFLAGS += -fno-stack-protector -pg
+STACK_PROT_CFLAGS += -fstack-protector-all
CPPFLAGS += -DSTACK_CHECK_ENABLED
+CFLAGS += -pg
+else
+STACK_PROT_CFLAGS += -fstack-protector
+STACK_PROT_CFLAGS += $(call try-cflag,$(CC),-fstack-protector-strong)
+endif
+
+ifeq ($(HAS_STACK_PROT),1)
+CPPFLAGS += -DHAS_STACK_PROT
+CFLAGS += $(STACK_PROT_CFLAGS)
else
CFLAGS += -fno-stack-protector
-#CFLAGS += -fstack-protector
-#CFLAGS += $(call try-cflag,$(CC),-fstack-protector-strong)
endif
+
CFLAGS += $(call try-cflag,$(CC),-Wjump-misses-init) \
$(call try-cflag,$(CC),-Wsuggest-attribute=const) \
$(call try-cflag,$(CC),-Wsuggest-attribute=noreturn) \
diff --git a/asm/head.S b/asm/head.S
index eccf0702..264899b1 100644
--- a/asm/head.S
+++ b/asm/head.S
@@ -389,6 +389,11 @@ boot_entry:
li %r0,0
std %r0,CPUTHREAD_STACK_BOT_MARK(%r13)
#endif
+ /* Initialize the stack guard */
+ LOAD_IMM64(%r3,STACK_CHECK_GUARD_BASE);
+ xor %r3,%r3,%r31
+ std %r3,0(%r13)
+
/* Jump to C */
mr %r3,%r27
bl main_cpu_entry
diff --git a/core/cpu.c b/core/cpu.c
index b94e04ef..7dd7c863 100644
--- a/core/cpu.c
+++ b/core/cpu.c
@@ -822,6 +822,7 @@ static void init_cpu_thread(struct cpu_thread *t,
init_lock(&t->dctl_lock);
init_lock(&t->job_lock);
list_head_init(&t->job_queue);
+ t->stack_guard = STACK_CHECK_GUARD_BASE ^ pir;
t->state = state;
t->pir = pir;
#ifdef STACK_CHECK_ENABLED
@@ -865,7 +866,8 @@ void __nomcount pre_init_boot_cpu(void)
{
struct cpu_thread *cpu = this_cpu();
- memset(cpu, 0, sizeof(struct cpu_thread));
+ /* We skip the stack guard ! */
+ memset(((void *)cpu) + 8, 0, sizeof(struct cpu_thread) - 8);
}
void init_boot_cpu(void)
@@ -943,8 +945,14 @@ void init_boot_cpu(void)
top_of_ram += (cpu_max_pir + 1) * STACK_SIZE;
/* Clear the CPU structs */
- for (i = 0; i <= cpu_max_pir; i++)
+ for (i = 0; i <= cpu_max_pir; i++) {
+ /* boot CPU already cleared and we don't want to clobber
+ * its stack guard value.
+ */
+ if (i == pir)
+ continue;
memset(&cpu_stacks[i].cpu, 0, sizeof(struct cpu_thread));
+ }
/* Setup boot CPU state */
boot_cpu = &cpu_stacks[pir].cpu;
diff --git a/core/utils.c b/core/utils.c
index d21881ef..9e2cb37c 100644
--- a/core/utils.c
+++ b/core/utils.c
@@ -22,9 +22,6 @@
#include <cpu.h>
#include <stack.h>
-extern unsigned long __stack_chk_guard;
-unsigned long __stack_chk_guard = 0xdeadf00dbaad300dULL;
-
void __noreturn assert_fail(const char *msg)
{
/**
diff --git a/include/cpu.h b/include/cpu.h
index 28041057..e3bc75f4 100644
--- a/include/cpu.h
+++ b/include/cpu.h
@@ -45,6 +45,11 @@ struct cpu_job;
struct xive_cpu_state;
struct cpu_thread {
+ /*
+ * "stack_guard" must be at offset 0 to match the
+ * -mstack-protector-guard-offset=0 statement in the Makefile
+ */
+ uint64_t stack_guard;
uint32_t pir;
uint32_t server_no;
uint32_t chip_id;
diff --git a/include/stack.h b/include/stack.h
index 3c9799b1..e50b34f0 100644
--- a/include/stack.h
+++ b/include/stack.h
@@ -44,6 +44,8 @@
*/
#define STACK_WARNING_GAP 2048
+#define STACK_CHECK_GUARD_BASE 0xdeadf00dbaad300
+
#ifndef __ASSEMBLY__
#include <stdint.h>
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