This prepare kernel to operate with a different value than userspace
AMR/IAMR.
For this, AMR/IAMR need 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. We don't need to modify IAMR value in
similar fashion.
If MMU_FTR_PKEY is enabled we need to save AMR/IAMR in pt_regs on
entering
kernel from userspace. If not we can assume that AMR/IAMR is not modified
from userspace.
We need to save AMR if we have MMU_FTR_KUAP feature enabled and we are
interrupted within kernel. This is required so that if we get interrupted
within copy_to/from_user we continue with the right AMR value.
If we hae MMU_FTR_KUEP enabled we need to restore IAMR on return to
userspace
beause kernel will be running with a different IAMR value.
Reviewed-by: Sandipan Das <sandi...@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
arch/powerpc/include/asm/book3s/64/kup.h | 222 +++++++++++++++++++----
arch/powerpc/include/asm/ptrace.h | 5 +-
arch/powerpc/kernel/asm-offsets.c | 2 +
arch/powerpc/kernel/entry_64.S | 6 +-
arch/powerpc/kernel/exceptions-64s.S | 4 +-
arch/powerpc/kernel/syscall_64.c | 32 +++-
6 files changed, 225 insertions(+), 46 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/kup.h
b/arch/powerpc/include/asm/book3s/64/kup.h
index 1d38eab83d48..4dbb2d53fd8f 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -13,17 +13,46 @@
#ifdef __ASSEMBLY__
-.macro kuap_restore_amr gpr1, gpr2
-#ifdef CONFIG_PPC_KUAP
+.macro kuap_restore_user_amr gpr1
+#if defined(CONFIG_PPC_PKEY)
BEGIN_MMU_FTR_SECTION_NESTED(67)
- mfspr \gpr1, SPRN_AMR
+ /*
+ * AMR and IAMR are going to be different when
+ * returning to userspace.
+ */
+ ld \gpr1, STACK_REGS_AMR(r1)
+ isync
+ mtspr SPRN_AMR, \gpr1
+ /*
+ * Restore IAMR only when returning to userspace
+ */
+ ld \gpr1, STACK_REGS_IAMR(r1)
+ mtspr SPRN_IAMR, \gpr1
+
+ /* No isync required, see kuap_restore_user_amr() */
+ END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_PKEY, 67)
+#endif
+.endm
+
+.macro kuap_restore_kernel_amr gpr1, gpr2
+#if defined(CONFIG_PPC_PKEY)
+
+ BEGIN_MMU_FTR_SECTION_NESTED(67)
+ /*
+ * AMR is going to be mostly the same since we are
+ * returning to the kernel. Compare and do a mtspr.
+ */
ld \gpr2, STACK_REGS_AMR(r1)
+ mfspr \gpr1, SPRN_AMR
cmpd \gpr1, \gpr2
- beq 998f
+ beq 100f
isync
mtspr SPRN_AMR, \gpr2
- /* No isync required, see kuap_restore_amr() */
-998:
+ /*
+ * No isync required, see kuap_restore_amr()
+ * No need to restore IAMR when returning to kernel space.
+ */
+100:
END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 67)
#endif
.endm
@@ -42,23 +71,98 @@
.endm
#endif
+/*
+ * if (pkey) {
+ *
+ * save AMR -> stack;
+ * if (kuap) {
+ * if (AMR != BLOCKED)
+ * KUAP_BLOCKED -> AMR;
+ * }
+ * if (from_user) {
+ * save IAMR -> stack;
+ * if (kuep) {
+ * KUEP_BLOCKED ->IAMR
+ * }
+ * }
+ * return;
+ * }
+ *
+ * if (kuap) {
+ * if (from_kernel) {
+ * save AMR -> stack;
+ * if (AMR != BLOCKED)
+ * KUAP_BLOCKED -> AMR;
+ * }
+ *
+ * }
+ */
.macro kuap_save_amr_and_lock gpr1, gpr2, use_cr, msr_pr_cr
-#ifdef CONFIG_PPC_KUAP
+#if defined(CONFIG_PPC_PKEY)
+
+ /*
+ * if both pkey and kuap is disabled, nothing to do
+ */
+ BEGIN_MMU_FTR_SECTION_NESTED(68)
+ b 100f // skip_save_amr
+ END_MMU_FTR_SECTION_NESTED_IFCLR(MMU_FTR_PKEY | MMU_FTR_KUAP, 68)
+
+ /*
+ * if pkey is disabled and we are entering from userspace
+ * don't do anything.
+ */
BEGIN_MMU_FTR_SECTION_NESTED(67)
.ifnb \msr_pr_cr
- bne \msr_pr_cr, 99f
+ /*
+ * Without pkey we are not changing AMR outside the kernel
+ * hence skip this completely.
+ */
+ bne \msr_pr_cr, 100f // from userspace
.endif
+ END_MMU_FTR_SECTION_NESTED_IFCLR(MMU_FTR_PKEY, 67)
+
+ /*
+ * pkey is enabled or pkey is disabled but entering from kernel
+ */
mfspr \gpr1, SPRN_AMR
std \gpr1, STACK_REGS_AMR(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)
+
+ /*
+ * if entering from kernel we don't need save IAMR
+ */
+ .ifnb \msr_pr_cr
+ beq \msr_pr_cr, 100f // from kernel space
+ mfspr \gpr1, SPRN_IAMR
+ std \gpr1, STACK_REGS_IAMR(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)
+ mtspr SPRN_IAMR, \gpr2
+ isync
+ END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUEP, 70)
+ .endif
+
+100: // skip_save_amr
#endif
.endm
@@ -66,22 +170,42 @@
DECLARE_STATIC_KEY_FALSE(uaccess_flush_key);
-#ifdef CONFIG_PPC_KUAP
+#ifdef CONFIG_PPC_PKEY
#include <asm/mmu.h>
#include <asm/ptrace.h>
-static inline void kuap_restore_amr(struct pt_regs *regs, unsigned
long amr)
+static inline void kuap_restore_user_amr(struct pt_regs *regs)
