From 90b39366d834e4de622f14a29ddb9f9f84d39d79 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 28 Oct 2020 09:04:33 +0100 Subject: [PATCH] powerpc: Avoid broken GCC __attribute__((optimize)) [ Upstream commit a7223f5bfcaeade4a86d35263493bcda6c940891 ] Commit 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot") introduced a couple of uses of __attribute__((optimize)) with function scope, to disable the stack protector in some early boot code. Unfortunately, and this is documented in the GCC man pages [0], overriding function attributes for optimization is broken, and is only supported for debug scenarios, not for production: the problem appears to be that setting GCC -f flags using this method will cause it to forget about some or all other optimization settings that have been applied. So the only safe way to disable the stack protector is to disable it for the entire source file. [0] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html Fixes: 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot") Signed-off-by: Ard Biesheuvel [mpe: Drop one remaining use of __nostackprotector, reported by snowpatch] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20201028080433.26799-1-ardb@kernel.org Signed-off-by: Sasha Levin --- arch/powerpc/kernel/Makefile | 3 +++ arch/powerpc/kernel/paca.c | 4 ++-- arch/powerpc/kernel/setup.h | 6 ------ arch/powerpc/kernel/setup_64.c | 2 +- 4 files changed, 6 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 59260eb96291..afbd47b0a75c 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -181,6 +181,9 @@ KCOV_INSTRUMENT_cputable.o := n KCOV_INSTRUMENT_setup_64.o := n KCOV_INSTRUMENT_paca.o := n +CFLAGS_setup_64.o += -fno-stack-protector +CFLAGS_paca.o += -fno-stack-protector + extra-$(CONFIG_PPC_FPU) += fpu.o extra-$(CONFIG_ALTIVEC) += vector.o extra-$(CONFIG_PPC64) += entry_64.o diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c index 4ea0cca52e16..c786adfb9413 100644 --- a/arch/powerpc/kernel/paca.c +++ b/arch/powerpc/kernel/paca.c @@ -176,7 +176,7 @@ static struct slb_shadow * __init new_slb_shadow(int cpu, unsigned long limit) struct paca_struct **paca_ptrs __read_mostly; EXPORT_SYMBOL(paca_ptrs); -void __init __nostackprotector initialise_paca(struct paca_struct *new_paca, int cpu) +void __init initialise_paca(struct paca_struct *new_paca, int cpu) { #ifdef CONFIG_PPC_PSERIES new_paca->lppaca_ptr = NULL; @@ -205,7 +205,7 @@ void __init __nostackprotector initialise_paca(struct paca_struct *new_paca, int } /* Put the paca pointer into r13 and SPRG_PACA */ -void __nostackprotector setup_paca(struct paca_struct *new_paca) +void setup_paca(struct paca_struct *new_paca) { /* Setup r13 */ local_paca = new_paca; diff --git a/arch/powerpc/kernel/setup.h b/arch/powerpc/kernel/setup.h index 1b02d338a5f5..c82577c4b15d 100644 --- a/arch/powerpc/kernel/setup.h +++ b/arch/powerpc/kernel/setup.h @@ -8,12 +8,6 @@ #ifndef __ARCH_POWERPC_KERNEL_SETUP_H #define __ARCH_POWERPC_KERNEL_SETUP_H -#ifdef CONFIG_CC_IS_CLANG -#define __nostackprotector -#else -#define __nostackprotector __attribute__((__optimize__("no-stack-protector"))) -#endif - void initialize_cache_info(void); void irqstack_early_init(void); diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 480c236724da..5bc7e753df4d 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -284,7 +284,7 @@ void __init record_spr_defaults(void) * device-tree is not accessible via normal means at this point. */ -void __init __nostackprotector early_setup(unsigned long dt_ptr) +void __init early_setup(unsigned long dt_ptr) { static __initdata struct paca_struct boot_paca;