[PATCH v2 2/3] lkdtm/powerpc: Add SLB multihit test

[Ganesh Goudar <ganeshgr@linux.ibm.com>]

Add support to inject slb multihit errors, to test machine
check handling.

Based on work by Mahesh Salgaonkar and Michal Suchánek.

Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
---
 drivers/misc/lkdtm/Makefile  |   4 ++
 drivers/misc/lkdtm/core.c    |   3 +
 drivers/misc/lkdtm/lkdtm.h   |   3 +
 drivers/misc/lkdtm/powerpc.c | 132 +++++++++++++++++++++++++++++++++++
 4 files changed, 142 insertions(+)
 create mode 100644 drivers/misc/lkdtm/powerpc.c

diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
index c70b3822013f..6a82f407fbcd 100644
--- a/drivers/misc/lkdtm/Makefile
+++ b/drivers/misc/lkdtm/Makefile
@@ -11,6 +11,10 @@ lkdtm-$(CONFIG_LKDTM)		+= usercopy.o
 lkdtm-$(CONFIG_LKDTM)		+= stackleak.o
 lkdtm-$(CONFIG_LKDTM)		+= cfi.o
 
+ifeq ($(CONFIG_PPC64),y)
+lkdtm-$(CONFIG_LKDTM)		+= powerpc.o
+endif
+
 KASAN_SANITIZE_stackleak.o	:= n
 KCOV_INSTRUMENT_rodata.o	:= n
 
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index a5e344df9166..8d5db42baa90 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -178,6 +178,9 @@ static const struct crashtype crashtypes[] = {
 #ifdef CONFIG_X86_32
 	CRASHTYPE(DOUBLE_FAULT),
 #endif
+#ifdef CONFIG_PPC64
+	CRASHTYPE(PPC_SLB_MULTIHIT),
+#endif
 };
 
 
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 8878538b2c13..b305bd511ee5 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -104,4 +104,7 @@ void lkdtm_STACKLEAK_ERASING(void);
 /* cfi.c */
 void lkdtm_CFI_FORWARD_PROTO(void);
 
+/* powerpc.c */
+void lkdtm_PPC_SLB_MULTIHIT(void);
+
 #endif
diff --git a/drivers/misc/lkdtm/powerpc.c b/drivers/misc/lkdtm/powerpc.c
new file mode 100644
index 000000000000..d6db18444757
--- /dev/null
+++ b/drivers/misc/lkdtm/powerpc.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+static inline unsigned long get_slb_index(void)
+{
+	unsigned long index;
+
+	index = get_paca()->stab_rr;
+
+	/*
+	 * simple round-robin replacement of slb starting at SLB_NUM_BOLTED.
+	 */
+	if (index < (mmu_slb_size - 1))
+		index++;
+	else
+		index = SLB_NUM_BOLTED;
+	get_paca()->stab_rr = index;
+	return index;
+}
+
+#define slb_esid_mask(ssize)	\
+	(((ssize) == MMU_SEGSIZE_256M) ? ESID_MASK : ESID_MASK_1T)
+
+static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
+					 unsigned long slot)
+{
+	return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | slot;
+}
+
+#define slb_vsid_shift(ssize)	\
+	((ssize) == MMU_SEGSIZE_256M ? SLB_VSID_SHIFT : SLB_VSID_SHIFT_1T)
+
+static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
+					 unsigned long flags)
+{
+	return (get_kernel_vsid(ea, ssize) << slb_vsid_shift(ssize)) | flags |
+		((unsigned long)ssize << SLB_VSID_SSIZE_SHIFT);
+}
+
+static void insert_slb_entry(char *p, int ssize)
+{
+	unsigned long flags, entry;
+
+	flags = SLB_VSID_KERNEL | mmu_psize_defs[MMU_PAGE_64K].sllp;
+	preempt_disable();
+
+	entry = get_slb_index();
+	asm volatile("slbmte %0,%1" :
+			: "r" (mk_vsid_data((unsigned long)p, ssize, flags)),
+			  "r" (mk_esid_data((unsigned long)p, ssize, entry))
+			: "memory");
+
+	entry = get_slb_index();
+	asm volatile("slbmte %0,%1" :
+			: "r" (mk_vsid_data((unsigned long)p, ssize, flags)),
+			  "r" (mk_esid_data((unsigned long)p, ssize, entry))
+			: "memory");
+	preempt_enable();
+	p[0] = '!';
+}
+
+static void inject_vmalloc_slb_multihit(void)
+{
+	char *p;
+
+	p = vmalloc(2048);
+	if (!p)
+		return;
+
+	insert_slb_entry(p, MMU_SEGSIZE_1T);
+	vfree(p);
+}
+
+static void inject_kmalloc_slb_multihit(void)
+{
+	char *p;
+
+	p = kmalloc(2048, GFP_KERNEL);
+	if (!p)
+		return;
+
+	insert_slb_entry(p, MMU_SEGSIZE_1T);
+	kfree(p);
+}
+
+static void insert_dup_slb_entry_0(void)
+{
+	unsigned long test_address = 0xC000000000000000;
+	volatile unsigned long *test_ptr;
+	unsigned long entry, i = 0;
+	unsigned long esid, vsid;
+
+	test_ptr = (unsigned long *)test_address;
+	preempt_disable();
+
+	asm volatile("slbmfee  %0,%1" : "=r" (esid) : "r" (i));
+	asm volatile("slbmfev  %0,%1" : "=r" (vsid) : "r" (i));
+	entry = get_slb_index();
+
+	/* for i !=0 we would need to mask out the old entry number */
+	asm volatile("slbmte %0,%1" :
+			: "r" (vsid),
+			  "r" (esid | entry)
+			: "memory");
+
+	asm volatile("slbmfee  %0,%1" : "=r" (esid) : "r" (i));
+	asm volatile("slbmfev  %0,%1" : "=r" (vsid) : "r" (i));
+	entry = get_slb_index();
+
+	/* for i !=0 we would need to mask out the old entry number */
+	asm volatile("slbmte %0,%1" :
+			: "r" (vsid),
+			  "r" (esid | entry)
+			: "memory");
+
+	pr_info("lkdtm: %s accessing test address 0x%lx: 0x%lx\n",
+		__func__, test_address, *test_ptr);
+
+	preempt_enable();
+}
+
+void lkdtm_PPC_SLB_MULTIHIT(void)
+{
+	if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
+		inject_vmalloc_slb_multihit();
+		inject_kmalloc_slb_multihit();
+		insert_dup_slb_entry_0();
+	}
+	pr_info("Recovered from SLB multihit. (Ignore this message on non HPTE machines)");
+}
-- 
2.26.2