[PATCH 6/7] powerpc/book3s32: Prepare Kernel Userspace Access Protection
Christophe Leroy
christophe.leroy at c-s.fr
Wed Mar 6 08:18:20 AEDT 2019
This patch prepares Kernel Userspace Access Protection for
book3s/32.
Due to limitations of the processor page protection capabilities,
the protection is only against writing. read protection cannot be
achieved using page protection.
book3s/32 provides the following values for PP bits:
PP00 provides RW for Key 0 and NA for Key 1
PP01 provides RW for Key 0 and RO for Key 1
PP10 provides RW for all
PP11 provides RO for all
Today PP10 is used for RW pages and PP11 for RO pages, and user
segment register's Kp and Ks are set to 1. This patch modifies
page protection to use PP01 for RW pages and sets user segment
registers to Kp 0 and Ks 0.
This will allow to setup Userspace write access protection by
settng Ks to 1 in the following patch.
Kernel space segment registers remain unchanged.
Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
arch/powerpc/include/asm/book3s/32/mmu-hash.h | 4 ++++
arch/powerpc/kernel/head_32.S | 28 ++++++++++++++++-----------
arch/powerpc/mm/hash_low_32.S | 6 +++---
3 files changed, 24 insertions(+), 14 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/mmu-hash.h b/arch/powerpc/include/asm/book3s/32/mmu-hash.h
index 5cb588395fdc..82492dcfa81c 100644
--- a/arch/powerpc/include/asm/book3s/32/mmu-hash.h
+++ b/arch/powerpc/include/asm/book3s/32/mmu-hash.h
@@ -63,6 +63,10 @@ typedef pte_t *pgtable_t;
#define PP_RWRW 2 /* Supervisor read/write, User read/write */
#define PP_RXRX 3 /* Supervisor read, User read */
+/* Values for Segment Registers */
+#define SR_KS 0x40000000 /* Supervisor key */
+#define SR_KP 0x20000000 /* User key */
+
#ifndef __ASSEMBLY__
/*
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index ce6a972f2584..46b633514422 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -522,9 +522,9 @@ InstructionTLBMiss:
andc. r1,r1,r0 /* check access & ~permission */
bne- InstructionAddressInvalid /* return if access not permitted */
/* Convert linux-style PTE to low word of PPC-style PTE */
- rlwimi r0,r0,32-1,30,30 /* _PAGE_USER -> PP msb */
- ori r1, r1, 0xe05 /* clear out reserved bits */
- andc r1, r0, r1 /* PP = user? 2 : 0 */
+ rlwimi r0,r0,32-2,31,31 /* _PAGE_USER -> PP lsb */
+ ori r1, r1, 0xe06 /* clear out reserved bits */
+ andc r1, r0, r1 /* PP = user? 1 : 0 */
BEGIN_FTR_SECTION
rlwinm r1,r1,0,~_PAGE_COHERENT /* clear M (coherence not required) */
END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
@@ -590,11 +590,11 @@ DataLoadTLBMiss:
* we would need to update the pte atomically with lwarx/stwcx.
*/
/* Convert linux-style PTE to low word of PPC-style PTE */
- rlwinm r1,r0,32-10,31,31 /* _PAGE_RW -> PP lsb */
+ rlwinm r1,r0,32-9,30,30 /* _PAGE_RW -> PP msb */
rlwimi r0,r0,32-1,30,30 /* _PAGE_USER -> PP msb */
rlwimi r0,r0,32-1,31,31 /* _PAGE_USER -> PP lsb */
ori r1,r1,0xe04 /* clear out reserved bits */
- andc r1,r0,r1 /* PP = user? rw? 2: 3: 0 */
+ andc r1,r0,r1 /* PP = user? rw? 1: 3: 0 */
BEGIN_FTR_SECTION
rlwinm r1,r1,0,~_PAGE_COHERENT /* clear M (coherence not required) */
END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
@@ -670,9 +670,9 @@ DataStoreTLBMiss:
* we would need to update the pte atomically with lwarx/stwcx.
*/
/* Convert linux-style PTE to low word of PPC-style PTE */
- rlwimi r0,r0,32-1,30,30 /* _PAGE_USER -> PP msb */
- li r1,0xe05 /* clear out reserved bits & PP lsb */
- andc r1,r0,r1 /* PP = user? 2: 0 */
+ rlwimi r0,r0,32-2,31,31 /* _PAGE_USER -> PP lsb */
+ li r1,0xe06 /* clear out reserved bits & PP msb */
+ andc r1,r0,r1 /* PP = user? 1: 0 */
BEGIN_FTR_SECTION
rlwinm r1,r1,0,~_PAGE_COHERENT /* clear M (coherence not required) */
END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
@@ -897,14 +897,21 @@ load_up_mmu:
tophys(r6,r6)
lwz r6,_SDR1 at l(r6)
mtspr SPRN_SDR1,r6
- li r0,16 /* load up segment register values */
+ li r0, NUM_USER_SEGMENTS /* load up user segment register values */
mtctr r0 /* for context 0 */
- lis r3,0x2000 /* Ku = 1, VSID = 0 */
+ li r3, 0 /* Kp = 0, Ks = 0, VSID = 0 */
li r4,0
3: mtsrin r3,r4
addi r3,r3,0x111 /* increment VSID */
addis r4,r4,0x1000 /* address of next segment */
bdnz 3b
+ li r0, 16 - NUM_USER_SEGMENTS /* load up kernel segment registers */
+ mtctr r0 /* for context 0 */
+ oris r3, r3, SR_KP at h /* Kp = 1 */
+3: mtsrin r3, r4
+ addi r3, r3, 0x111 /* increment VSID */
+ addis r4, r4, 0x1000 /* address of next segment */
+ bdnz 3b
/* Load the BAT registers with the values set up by MMU_init.
MMU_init takes care of whether we're on a 601 or not. */
@@ -1008,7 +1015,6 @@ _ENTRY(switch_mmu_context)
blt- 4f
mulli r3,r3,897 /* multiply context by skew factor */
rlwinm r3,r3,4,8,27 /* VSID = (context & 0xfffff) << 4 */
- addis r3,r3,0x6000 /* Set Ks, Ku bits */
li r0,NUM_USER_SEGMENTS
mtctr r0
diff --git a/arch/powerpc/mm/hash_low_32.S b/arch/powerpc/mm/hash_low_32.S
index 1f13494efb2b..37964878e392 100644
--- a/arch/powerpc/mm/hash_low_32.S
+++ b/arch/powerpc/mm/hash_low_32.S
@@ -309,13 +309,13 @@ Hash_msk = (((1 << Hash_bits) - 1) * 64)
_GLOBAL(create_hpte)
/* Convert linux-style PTE (r5) to low word of PPC-style PTE (r8) */
- rlwinm r8,r5,32-10,31,31 /* _PAGE_RW -> PP lsb */
- rlwinm r0,r5,32-7,31,31 /* _PAGE_DIRTY -> PP lsb */
+ rlwinm r8,r5,32-9,30,30 /* _PAGE_RW -> PP msb */
+ rlwinm r0,r5,32-6,30,30 /* _PAGE_DIRTY -> PP msb */
and r8,r8,r0 /* writable if _RW & _DIRTY */
rlwimi r5,r5,32-1,30,30 /* _PAGE_USER -> PP msb */
rlwimi r5,r5,32-2,31,31 /* _PAGE_USER -> PP lsb */
ori r8,r8,0xe04 /* clear out reserved bits */
- andc r8,r5,r8 /* PP = user? (rw&dirty? 2: 3): 0 */
+ andc r8,r5,r8 /* PP = user? (rw&dirty? 1: 3): 0 */
BEGIN_FTR_SECTION
rlwinm r8,r8,0,~_PAGE_COHERENT /* clear M (coherence not required) */
END_FTR_SECTION_IFCLR(CPU_FTR_NEED_COHERENT)
--
2.13.3
More information about the Linuxppc-dev
mailing list