[PATCH] x86/sgx: Add code to inject hwpoison into SGX memory

[Thomas Tai <thomas.tai@oracle.com>]

Inspired by commit c6acb1e7bf46 (x86/sgx: Add hook to error injection
address validation), add a similar code in hwpoison_inject function to
check if the address is located in SGX Memory. The error will then be
handled by the arch_memory_failure function in the SGX driver.

Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
---
 Documentation/mm/hwpoison.rst | 44 +++++++++++++++++++++++++++++++++++
 mm/hwpoison-inject.c          |  3 +++
 2 files changed, 47 insertions(+)

diff --git a/Documentation/mm/hwpoison.rst b/Documentation/mm/hwpoison.rst
index b9d5253c1305..8a542aca4744 100644
--- a/Documentation/mm/hwpoison.rst
+++ b/Documentation/mm/hwpoison.rst
@@ -162,6 +162,50 @@ Testing
 
   Some portable hwpoison test programs in mce-test, see below.
 
+* Special notes for injection into SGX enclaves
+
+  1) Determine physical address of enclave page
+
+	dmesg | grep "sgx: EPC"
+
+	sgx: EPC section 0x8000c00000-0x807f7fffff
+	sgx: EPC section 0x10000c00000-0x1007fffffff
+
+  2) Convert the EPC address to page frame number.
+
+	For 4K page size, the page frame number for 0x8000c00000 is
+	0x8000c00000 / 0x1000 = 0x8000c00.
+
+  3) Trace memory_failure
+
+	echo nop > /sys/kernel/tracing/current_tracer
+	echo *memory_failure > /sys/kernel/tracing/set_ftrace_filter
+	echo function > /sys/kernel/tracing/current_tracer
+
+  4) Inject a memory error
+
+	modprobe hwpoison-inject
+	echo "0x8000c00" > /sys/kernel/debug/hwpoison/corrupt-pfn
+
+  5) Check the trace output
+
+	cat /sys/kernel/tracing/trace
+
+	# tracer: function
+	#
+	# entries-in-buffer/entries-written: 2/2   #P:128
+	#
+	#                            _-----=> irqs-off
+	#                           / _----=> need-resched
+	#                          | / _---=> hardirq/softirq
+	#                          || / _--=> preempt-depth
+	#                          ||| / _-=> migrate-disable
+	#                          |||| /     delay
+	#       TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
+	#          | |         |   |||||     |         |
+	        bash-12167   [002] .....   113.136808: memory_failure<-simple_attr_write
+	        bash-12167   [002] .....   113.136810: arch_memory_failure<-memory_failure
+
 References
 ==========
 
diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
index 65e242b5a432..8134dc983699 100644
--- a/mm/hwpoison-inject.c
+++ b/mm/hwpoison-inject.c
@@ -21,6 +21,9 @@ static int hwpoison_inject(void *data, u64 val)
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
+	if (arch_is_platform_page(pfn << PAGE_SHIFT))
+		goto inject;
+
 	if (!pfn_valid(pfn))
 		return -ENXIO;
 
-- 
2.31.1