[PATCH 2/3] powerpc/mce: Add debugfs interface to inject MCE
Ganesh Goudar
ganeshgr at linux.ibm.com
Thu Sep 17 03:22:27 AEST 2020
To test machine check handling, add debugfs interface to inject
slb multihit errors.
To inject slb multihit:
#echo 1 > /sys/kernel/debug/powerpc/mce_error_inject/inject_slb_multihit
Signed-off-by: Ganesh Goudar <ganeshgr at linux.ibm.com>
Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
---
arch/powerpc/Kconfig.debug | 9 ++
arch/powerpc/sysdev/Makefile | 2 +
arch/powerpc/sysdev/mce_error_inject.c | 148 +++++++++++++++++++++++++
3 files changed, 159 insertions(+)
create mode 100644 arch/powerpc/sysdev/mce_error_inject.c
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index b88900f4832f..61db133f2f0d 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -398,3 +398,12 @@ config KASAN_SHADOW_OFFSET
hex
depends on KASAN
default 0xe0000000
+
+config MCE_ERROR_INJECT
+ bool "Enable MCE error injection through debugfs"
+ depends on DEBUG_FS
+ default y
+ help
+ This option creates an mce_error_inject directory in the
+ powerpc debugfs directory that allows limited injection of
+ Machine Check Errors (MCEs).
diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
index 026b3f01a991..7fc102222b77 100644
--- a/arch/powerpc/sysdev/Makefile
+++ b/arch/powerpc/sysdev/Makefile
@@ -52,3 +52,5 @@ obj-$(CONFIG_PPC_XICS) += xics/
obj-$(CONFIG_PPC_XIVE) += xive/
obj-$(CONFIG_GE_FPGA) += ge/
+
+obj-$(CONFIG_MCE_ERROR_INJECT) += mce_error_inject.o
diff --git a/arch/powerpc/sysdev/mce_error_inject.c b/arch/powerpc/sysdev/mce_error_inject.c
new file mode 100644
index 000000000000..ca4726bfa2d9
--- /dev/null
+++ b/arch/powerpc/sysdev/mce_error_inject.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Machine Check Exception injection code
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <asm/debugfs.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;
+ struct paca_struct *paca;
+
+ flags = SLB_VSID_KERNEL | mmu_psize_defs[MMU_PAGE_64K].sllp;
+
+ preempt_disable();
+
+ paca = get_paca();
+
+ 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 ssize_t inject_slb_multihit(const char __user *u_buf, size_t count)
+{
+ char buf[32];
+ size_t buf_size;
+
+ buf_size = min(count, (sizeof(buf) - 1));
+ if (copy_from_user(buf, u_buf, buf_size))
+ return -EFAULT;
+ buf[buf_size] = '\0';
+
+ if (buf[0] != '1')
+ return -EINVAL;
+
+ inject_vmalloc_slb_multihit();
+ inject_kmalloc_slb_multihit();
+ return count;
+}
+
+static ssize_t inject_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ static ssize_t (*func)(const char __user *, size_t);
+
+ func = file->f_inode->i_private;
+ return func(buf, count);
+}
+
+static const struct file_operations inject_fops = {
+ .write = inject_write,
+ .llseek = default_llseek,
+};
+
+static int mce_error_inject_setup(void)
+{
+ struct dentry *mce_error_inject_dir;
+
+ mce_error_inject_dir = debugfs_create_dir("mce_error_inject",
+ powerpc_debugfs_root);
+
+ if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
+ (void)debugfs_create_file("inject_slb_multihit", 0200,
+ mce_error_inject_dir,
+ &inject_slb_multihit,
+ &inject_fops);
+ }
+
+ return 0;
+}
+
+device_initcall(mce_error_inject_setup);
--
2.26.2
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