Home Home > GIT Browse
summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorRussell Currey <ruscur@russell.cc>2019-04-18 16:51:16 +1000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-05-16 19:40:30 +0200
commit0da52ad69b37346335848e0811467a3ffe6f0c68 (patch)
treefb3b1832522ef72e70423d64cd2f5a9fed8f4ef8
parentd314437d17adcbc696e61816972a9c35df084193 (diff)
powerpc/powernv/idle: Restore IAMR after idle
commit a3f3072db6cad40895c585dce65e36aab997f042 upstream. Without restoring the IAMR after idle, execution prevention on POWER9 with Radix MMU is overwritten and the kernel can freely execute userspace without faulting. This is necessary when returning from any stop state that modifies user state, as well as hypervisor state. To test how this fails without this patch, load the lkdtm driver and do the following: $ echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT which won't fault, then boot the kernel with powersave=off, where it will fault. Applying this patch will fix this. Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of user space") Cc: stable@vger.kernel.org # v4.10+ Signed-off-by: Russell Currey <ruscur@russell.cc> Reviewed-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/powerpc/kernel/idle_book3s.S20
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 7f5ac2e8581b..36178000a2f2 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -170,6 +170,9 @@ core_idle_lock_held:
bne- core_idle_lock_held
blr
+/* Reuse an unused pt_regs slot for IAMR */
+#define PNV_POWERSAVE_IAMR _DAR
+
/*
* Pass requested state in r3:
* r3 - PNV_THREAD_NAP/SLEEP/WINKLE in POWER8
@@ -200,6 +203,12 @@ pnv_powersave_common:
/* Continue saving state */
SAVE_GPR(2, r1)
SAVE_NVGPRS(r1)
+
+BEGIN_FTR_SECTION
+ mfspr r5, SPRN_IAMR
+ std r5, PNV_POWERSAVE_IAMR(r1)
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
+
mfcr r5
std r5,_CCR(r1)
std r1,PACAR1(r13)
@@ -924,6 +933,17 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
REST_NVGPRS(r1)
REST_GPR(2, r1)
+
+BEGIN_FTR_SECTION
+ /* IAMR was saved in pnv_powersave_common() */
+ ld r5, PNV_POWERSAVE_IAMR(r1)
+ mtspr SPRN_IAMR, r5
+ /*
+ * We don't need an isync here because the upcoming mtmsrd is
+ * execution synchronizing.
+ */
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
+
ld r4,PACAKMSR(r13)
ld r5,_LINK(r1)
ld r6,_CCR(r1)