powerpc/64: add stack protector support

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>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 3bcb059..602eea7 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -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

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 45b8eb4..81552c7 100644 (file)
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -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.

diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 7b6e23a..c6d01f0 100644 (file)
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -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);

diff --git a/arch/powerpc/include/asm/stackprotector.h b/arch/powerpc/include/asm/stackprotector.h
index d05d969..1c8460e 100644 (file)
--- a/arch/powerpc/include/asm/stackprotector.h
+++ b/arch/powerpc/include/asm/stackprotector.h
@@ -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 */

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 9e9ee16..a6d70fd 100644 (file)
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -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

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 77a888b..573fa87 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -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