This prepare kernel to operate with a different value than userspace IAMR. For this, IAMR needs to be saved and restored on entry and return from the kernel.
If MMU_FTR_KEY is enabled we always use the key mechanism to implement KUEP feature. If MMU_FTR_KEY is not supported and if we support MMU_FTR_KUEP (radix translation on POWER9), we can skip restoring IAMR on return to userspace. Userspace won't be using IAMR in that specific config. We don't need to save/restore IAMR on reentry into the kernel due to interrupt because the kernel doesn't modify IAMR internally. Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> --- arch/powerpc/include/asm/book3s/64/kup.h | 46 ++++++++++++++++++++++-- arch/powerpc/include/asm/ptrace.h | 6 +++- arch/powerpc/kernel/asm-offsets.c | 4 +++ arch/powerpc/kernel/syscall_64.c | 8 +++-- 4 files changed, 59 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h index 6979cd1a0003..49182efea945 100644 --- a/arch/powerpc/include/asm/book3s/64/kup.h +++ b/arch/powerpc/include/asm/book3s/64/kup.h @@ -17,15 +17,26 @@ #if defined(CONFIG_PPC_MEM_KEYS) BEGIN_MMU_FTR_SECTION_NESTED(67) /* - * AMR is going to be different when + * AMR and IAMR are going to be different when * returning to userspace. */ ld \gpr1, STACK_REGS_KUAP(r1) isync mtspr SPRN_AMR, \gpr1 + /* + * Restore IAMR only when returning to userspace + */ + ld \gpr1, STACK_REGS_KUEP(r1) + mtspr SPRN_IAMR, \gpr1 /* No isync required, see kuap_restore_user_amr() */ END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_PKEY , 67) + + /* + * We don't check KUEP feature here, because if FTR_PKEY + * is not enabled we don't need to restore IAMR on + * return to usespace. + */ #endif .endm @@ -53,6 +64,9 @@ isync mtspr SPRN_AMR, \gpr2 /* No isync required, see kuap_restore_amr() */ + /* + * No need to restore IAMR when returning to kernel space. + */ 100: // skip_restore_amr #endif .endm @@ -90,6 +104,12 @@ b 100f // skip_save_amr ALT_MMU_FTR_SECTION_END_NESTED_IFSET(MMU_FTR_KUAP, 68) + /* + * We don't check KUEP feature here, because if FTR_PKEY + * is not enabled we don't need to save IAMR on + * entry from usespace. That is handled by either + * handle_kuap_save_amr or skip_save_amr + */ 99: // handle_kuap_save_amr .ifnb \msr_pr_cr @@ -120,6 +140,25 @@ 102: END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 69) + .ifnb \msr_pr_cr + beq \msr_pr_cr, 103f // from kernel space + mfspr \gpr1, SPRN_IAMR + std \gpr1, STACK_REGS_KUEP(r1) + + /* + * update kernel IAMR with AMR_KUEP_BLOCKED only + * if KUEP feature is enabled + */ + BEGIN_MMU_FTR_SECTION_NESTED(70) + LOAD_REG_IMMEDIATE(\gpr2, AMR_KUEP_BLOCKED) + cmpd \use_cr, \gpr1, \gpr2 + beq \use_cr, 103f + mtspr SPRN_IAMR, \gpr2 + isync +103: + END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUEP, 70) + .endif + 100: // skip_save_amr #endif .endm @@ -140,13 +179,13 @@ static inline void kuap_restore_user_amr(struct pt_regs *regs) isync(); mtspr(SPRN_AMR, regs->kuap); + mtspr(SPRN_IAMR, regs->kuep); /* * No isync required here because we are about to rfi * back to previous context before any user accesses * would be made, which is a CSI. */ } - static inline void kuap_restore_kernel_amr(struct pt_regs *regs, unsigned long amr) { @@ -162,6 +201,9 @@ static inline void kuap_restore_kernel_amr(struct pt_regs *regs, */ } } + /* + * No need to restore IAMR when returning to kernel space. + */ } static inline unsigned long kuap_get_and_check_amr(void) diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h index 1a6cadf63d14..2b610dc20426 100644 --- a/arch/powerpc/include/asm/ptrace.h +++ b/arch/powerpc/include/asm/ptrace.h @@ -56,8 +56,12 @@ struct pt_regs #ifdef CONFIG_PPC_HAVE_KUAP unsigned long kuap; #endif +#ifdef CONFIG_PPC_HAVE_KUEP + unsigned long kuep; +#endif + }; - unsigned long __pad[2]; /* Maintain 16 byte interrupt stack alignment */ + unsigned long __pad[4]; /* Maintain 16 byte interrupt stack alignment */ }; }; #endif diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 1694c4f531b9..5b68970a52a7 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -357,6 +357,10 @@ int main(void) #ifdef CONFIG_PPC_HAVE_KUAP STACK_PT_REGS_OFFSET(STACK_REGS_KUAP, kuap); #endif +#ifdef CONFIG_PPC_HAVE_KUEP + STACK_PT_REGS_OFFSET(STACK_REGS_KUEP, kuep); +#endif + #if defined(CONFIG_PPC32) #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c index fded67982fbe..8229730c6cb5 100644 --- a/arch/powerpc/kernel/syscall_64.c +++ b/arch/powerpc/kernel/syscall_64.c @@ -37,15 +37,19 @@ notrace long system_call_exception(long r3, long r4, long r5, #ifdef CONFIG_PPC_MEM_KEYS if (mmu_has_feature(MMU_FTR_PKEY)) { - unsigned long amr; + unsigned long amr, iamr; /* - * When entering from userspace we mostly have the AMR + * When entering from userspace we mostly have the AMR/IAMR * different from kernel default values. Hence don't compare. */ amr = mfspr(SPRN_AMR); + iamr = mfspr(SPRN_IAMR); regs->kuap = amr; + regs->kuep = iamr; if (mmu_has_feature(MMU_FTR_KUAP)) mtspr(SPRN_AMR, AMR_KUAP_BLOCKED); + if (mmu_has_feature(MMU_FTR_KUEP)) + mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED); isync(); } else #endif -- 2.26.2