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powerpc/64: add stack protector support

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On PPC64, as register r13 points to the paca_struct at all time,
this patch adds a copy of the canary there, which is copied at
task_switch.
That new canary is then used by using the following GCC options:
-mstack-protector-guard=tls
-mstack-protector-guard-reg=r13
-mstack-protector-guard-offset=offsetof(struct paca_struct, canary))

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2018-09-27 07:05:55 +00:00 committed by Michael Ellerman
parent c3ff2a5193
commit 06ec27aea9
6 changed files with 23 additions and 1 deletions
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2
arch/powerpc/Kconfig
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@ -180,7 +180,7 @@ config PPC
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_CBPF_JIT if !PPC64
select HAVE_STACKPROTECTOR if $(cc-option,-mstack-protector-guard=tls) && PPC32
select HAVE_STACKPROTECTOR if $(cc-option,-mstack-protector-guard=tls)
select HAVE_CONTEXT_TRACKING if PPC64
select HAVE_DEBUG_KMEMLEAK
select HAVE_DEBUG_STACKOVERFLOW

8
arch/powerpc/Makefile
View File

@ -113,7 +113,11 @@ KBUILD_ARFLAGS += --target=elf$(BITS)-$(GNUTARGET)
endif
cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard=tls
ifdef CONFIG_PPC64
cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard-reg=r13
else
cflags-$(CONFIG_STACKPROTECTOR) += -mstack-protector-guard-reg=r2
endif
LDFLAGS_vmlinux-y := -Bstatic
LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
@ -411,8 +415,12 @@ ifdef CONFIG_STACKPROTECTOR
prepare: stack_protector_prepare
stack_protector_prepare: prepare0
ifdef CONFIG_PPC64
$(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "PACA_CANARY") print $$3;}' include/generated/asm-offsets.h))
else
$(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "TASK_CANARY") print $$3;}' include/generated/asm-offsets.h))
endif
endif
# Use the file '.tmp_gas_check' for binutils tests, as gas won't output
# to stdout and these checks are run even on install targets.

3
arch/powerpc/include/asm/paca.h
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@ -256,6 +256,9 @@ struct paca_struct {
struct slb_entry *mce_faulty_slbs;
u16 slb_save_cache_ptr;
#endif /* CONFIG_PPC_BOOK3S_64 */
#ifdef CONFIG_STACKPROTECTOR
unsigned long canary;
#endif
} ____cacheline_aligned;
extern void copy_mm_to_paca(struct mm_struct *mm);

4
arch/powerpc/include/asm/stackprotector.h
View File

@ -11,6 +11,7 @@
#include <linux/version.h>
#include <asm/reg.h>
#include <asm/current.h>
#include <asm/paca.h>
/*
* Initialize the stackprotector canary value.
@ -29,6 +30,9 @@ static __always_inline void boot_init_stack_canary(void)
canary &= CANARY_MASK;
current->stack_canary = canary;
#ifdef CONFIG_PPC64
get_paca()->canary = canary;
#endif
}
#endif /* _ASM_STACKPROTECTOR_H */

3
arch/powerpc/kernel/asm-offsets.c
View File

@ -81,6 +81,9 @@ int main(void)
OFFSET(MM, task_struct, mm);
#ifdef CONFIG_STACKPROTECTOR
OFFSET(TASK_CANARY, task_struct, stack_canary);
#ifdef CONFIG_PPC64
OFFSET(PACA_CANARY, paca_struct, canary);
#endif
#endif
OFFSET(MMCONTEXTID, mm_struct, context.id);
#ifdef CONFIG_PPC64

4
arch/powerpc/kernel/entry_64.S
View File

@ -624,6 +624,10 @@ _GLOBAL(_switch)
addi r6,r4,-THREAD /* Convert THREAD to 'current' */
std r6,PACACURRENT(r13) /* Set new 'current' */
#if defined(CONFIG_STACKPROTECTOR)
ld r6, TASK_CANARY(r6)
std r6, PACA_CANARY(r13)
#endif
ld r8,KSP(r4) /* new stack pointer */
#ifdef CONFIG_PPC_BOOK3S_64