@@ -13,13 +13,32 @@
#ifdef __ASSEMBLY__
-.macro kuap_restore_amr gpr
-#ifdef CONFIG_PPC_KUAP
+.macro kuap_restore_amr gpr to_user
+#if defined(CONFIG_PPC_MEM_KEYS) || defined (CONFIG_PPC_KUAP)
BEGIN_MMU_FTR_SECTION_NESTED(67)
+ b 101f // handle_pkey_restore_amr
+ END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_PKEY , 67)
+
+ BEGIN_MMU_FTR_SECTION_NESTED(68)
+ b 99f // handle_kuap_restore_amr
+ MMU_FTR_SECTION_ELSE_NESTED(68)
+ b 100f // skip_restore_amr
+ ALT_MMU_FTR_SECTION_END_NESTED_IFSET(MMU_FTR_KUAP, 68)
+
+99: // handle_kuap_restore_amr
+ /*
+ * No key support, don't bother to restore AMR
+ * when returning to userspace.
+ */
+ .ifnb \to_user
+ b 100f
+ .endif
+101: // handle_pkey_restore_amr
ld \gpr, STACK_REGS_KUAP(r1)
isync
mtspr SPRN_AMR, \gpr
- END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 67)
+ /* No isync here because we will return to a different context */
+100: // skip_restore_amr
#endif
.endm
@@ -35,23 +54,58 @@
#endif
.endm
+/*
+ * MMU_FTR_PKEY and MMU_FTR_KUAP can both be enabled on a platform. We prefer
+ * PKEY over KUAP if both can be enabled on the platform.
+ *
+ * With KUAP only enabled on exception if we are coming from userspace we don't
+ * save the AMR at all, because the expectation is that userspace can't change
+ * the AMR if KUAP feature is enabled.
+ */
.macro kuap_save_amr_and_lock gpr1, gpr2, use_cr, msr_pr_cr
-#ifdef CONFIG_PPC_KUAP
+#if defined(CONFIG_PPC_MEM_KEYS) || defined (CONFIG_PPC_KUAP)
+
BEGIN_MMU_FTR_SECTION_NESTED(67)
+ b 101f // handle_pkey_save_amr
+ END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_PKEY , 67)
+
+ BEGIN_MMU_FTR_SECTION_NESTED(68)
+ b 99f // handle_kuap_save_amr
+ MMU_FTR_SECTION_ELSE_NESTED(68)
+ b 100f // skip_save_amr
+ ALT_MMU_FTR_SECTION_END_NESTED_IFSET(MMU_FTR_KUAP, 68)
+
+
+99: // handle_kuap_save_amr
.ifnb \msr_pr_cr
- bne \msr_pr_cr, 99f
+ /*
+ * We avoid changing AMR outside the kernel
+ * hence skip this completely.
+ */
+ bne \msr_pr_cr, 100f // from userspace
.endif
+
+101: // handle_pkey_save_amr
mfspr \gpr1, SPRN_AMR
std \gpr1, STACK_REGS_KUAP(r1)
- li \gpr2, (AMR_KUAP_BLOCKED >> AMR_KUAP_SHIFT)
- sldi \gpr2, \gpr2, AMR_KUAP_SHIFT
+
+ /*
+ * update kernel AMR with AMR_KUAP_BLOCKED only
+ * if KUAP feature is enabled
+ */
+ BEGIN_MMU_FTR_SECTION_NESTED(69)
+ LOAD_REG_IMMEDIATE(\gpr2, AMR_KUAP_BLOCKED)
cmpd \use_cr, \gpr1, \gpr2
- beq \use_cr, 99f
- // We don't isync here because we very recently entered via rfid
+ beq \use_cr, 102f
+ /*
+ * We don't isync here because we very recently entered via an interrupt
+ */
mtspr SPRN_AMR, \gpr2
isync
-99:
- END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 67)
+102:
+ END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 69)
+
+100: // skip_save_amr
#endif
.endm
@@ -62,9 +116,12 @@
#include <asm/mmu.h>
#include <asm/ptrace.h>
-static inline void kuap_restore_amr(struct pt_regs *regs)
+static inline void kuap_restore_amr(struct pt_regs *regs, bool to_user)
{
- if (mmu_has_feature(MMU_FTR_KUAP)) {
+ if (!mmu_has_feature(MMU_FTR_PKEY) && to_user)
+ return;
+
+ if (mmu_has_feature(MMU_FTR_KUAP) || mmu_has_feature(MMU_FTR_PKEY)) {
isync();
mtspr(SPRN_AMR, regs->kuap);
/*
@@ -76,7 +133,8 @@ static inline void kuap_restore_amr(struct pt_regs *regs)
static inline void kuap_check_amr(void)
{
- if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) && mmu_has_feature(MMU_FTR_KUAP))
+ if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG) &&
+ (mmu_has_feature(MMU_FTR_KUAP) || mmu_has_feature(MMU_FTR_PKEY)))
WARN_ON_ONCE(mfspr(SPRN_AMR) != AMR_KUAP_BLOCKED);
}
@@ -481,7 +481,7 @@ _ASM_NOKPROBE_SYMBOL(fast_interrupt_return)
kuap_check_amr r3, r4
ld r4,_MSR(r1)
andi. r0,r4,MSR_PR
- bne .Lfast_user_interrupt_return
+ bne .Lfast_user_interrupt_return_amr
kuap_restore_amr r3
andi. r0,r4,MSR_RI
li r3,0 /* 0 return value, no EMULATE_STACK_STORE */
@@ -502,6 +502,8 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return)
cmpdi r3,0
bne- .Lrestore_nvgprs
+.Lfast_user_interrupt_return_amr:
+ kuap_restore_amr r3, 1
.Lfast_user_interrupt_return:
ld r11,_NIP(r1)
ld r12,_MSR(r1)
@@ -35,7 +35,15 @@ notrace long system_call_exception(long r3, long r4, long r5,
BUG_ON(!FULL_REGS(regs));
BUG_ON(regs->softe != IRQS_ENABLED);
- kuap_check_amr();
+ if (mmu_has_feature(MMU_FTR_PKEY)) {
+ unsigned long amr;
+
+ amr = mfspr(SPRN_AMR);
+ regs->kuap = amr;
+ mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
+ isync();
+ } else
+ kuap_check_amr();
account_cpu_user_entry();
@@ -208,6 +216,10 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
account_cpu_user_exit();
+ /*
+ * We do this at the end so that we do context switch with KERNEL AMR
+ */
+ kuap_restore_amr(regs, true);
return ret;
}
@@ -293,9 +305,12 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
local_paca->tm_scratch = regs->msr;
#endif
-
account_cpu_user_exit();
+ /*
+ * We do this at the end so that we do context switch with KERNEL AMR
+ */
+ kuap_restore_amr(regs, true);
return ret;
}
This prepare kernel to operate with a different value than userspace AMR. For this, AMR needs to be saved and restored on entry and return from the kernel. With KUAP we modify kernel AMR when accessing user address from the kernel via copy_to/from_user interfaces. If MMU_FTR_KEY is enabled we always use the key mechanism to implement KUAP feature. If MMU_FTR_KEY is not supported and if we support MMU_FTR_KUAP (radix translation on POWER9), we can skip restoring AMR on return to userspace. Userspace won't be using AMR in that specific config. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> --- arch/powerpc/include/asm/book3s/64/kup.h | 86 ++++++++++++++++++++---- arch/powerpc/kernel/entry_64.S | 4 +- arch/powerpc/kernel/syscall_64.c | 19 +++++- 3 files changed, 92 insertions(+), 17 deletions(-)