[PATCH v3 05/11] powerpc/dexcr: Support userspace ROP protection
From: Benjamin Gray <hidden>
Date: 2023-06-16 03:54:48
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
The ISA 3.1B hashst and hashchk instructions use a per-cpu SPR HASHKEYR to hold a key used in the hash calculation. This key should be different for each process to make it harder for a malicious process to recreate valid hash values for a victim process. Add support for storing a per-thread hash key, and setting/clearing HASHKEYR appropriately. Signed-off-by: Benjamin Gray <redacted> Reviewed-by: Russell Currey <redacted> --- v3: * Add ruscur reviewed-by v1: * Guard HASHKEYR update behind change check * HASHKEYR reset moved earlier to patch 2 --- arch/powerpc/include/asm/processor.h | 1 + arch/powerpc/kernel/process.c | 17 +++++++++++++++++ 2 files changed, 18 insertions(+)
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index e96c9b8c2a60..8a6754ffdc7e 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h@@ -264,6 +264,7 @@ struct thread_struct { unsigned long mmcr3; unsigned long sier2; unsigned long sier3; + unsigned long hashkeyr; #endif };
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 1fefafb2b29b..b68898ac07e1 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c@@ -1182,6 +1182,9 @@ static inline void save_sprs(struct thread_struct *t) */ t->tar = mfspr(SPRN_TAR); } + + if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE)) + t->hashkeyr = mfspr(SPRN_HASHKEYR); #endif }
@@ -1260,6 +1263,10 @@ static inline void restore_sprs(struct thread_struct *old_thread, if (cpu_has_feature(CPU_FTR_P9_TIDR) && old_thread->tidr != new_thread->tidr) mtspr(SPRN_TIDR, new_thread->tidr); + + if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE) && + old_thread->hashkeyr != new_thread->hashkeyr) + mtspr(SPRN_HASHKEYR, new_thread->hashkeyr); #endif }
@@ -1867,6 +1874,10 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) } p->thread.tidr = 0; +#endif +#ifdef CONFIG_PPC_BOOK3S_64 + if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE)) + p->thread.hashkeyr = current->thread.hashkeyr; #endif return 0; }
@@ -1984,6 +1995,12 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp) current->thread.tm_tfiar = 0; current->thread.load_tm = 0; #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */ +#ifdef CONFIG_PPC_BOOK3S_64 + if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE)) { + current->thread.hashkeyr = get_random_long(); + mtspr(SPRN_HASHKEYR, current->thread.hashkeyr); + } +#endif /* CONFIG_PPC_BOOK3S_64 */ } EXPORT_SYMBOL(start_thread);
--
2.40.1