We have custom stack expansion checks that it turns out are extremely
badly tested and contain bugs, surprise. So add some tests that
exercise the code and capture the current boundary conditions.
The signal test currently fails on 64-bit kernels because the 2048
byte allowance for the signal frame is too small, we will fix that in
a subsequent patch.
Signed-off-by: Michael Ellerman
---
v2:
- Concentrate on used stack around the 1MB size, as that's where our
custom logic kicks in.
- Increment the used stack size by 64 so we can exercise the case
where we overflow the page by less than 128 (__SIGNAL_FRAMESIZE).
---
tools/testing/selftests/powerpc/mm/.gitignore | 2 +
tools/testing/selftests/powerpc/mm/Makefile | 9 +-
.../powerpc/mm/stack_expansion_ldst.c | 233 ++
.../powerpc/mm/stack_expansion_signal.c | 118 +
tools/testing/selftests/powerpc/pmu/lib.h | 1 +
5 files changed, 362 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/powerpc/mm/stack_expansion_ldst.c
create mode 100644 tools/testing/selftests/powerpc/mm/stack_expansion_signal.c
diff --git a/tools/testing/selftests/powerpc/mm/.gitignore
b/tools/testing/selftests/powerpc/mm/.gitignore
index 8d041f508a51..52308f42b7de 100644
--- a/tools/testing/selftests/powerpc/mm/.gitignore
+++ b/tools/testing/selftests/powerpc/mm/.gitignore
@@ -8,3 +8,5 @@ large_vm_fork_separation
bad_accesses
tlbie_test
pkey_exec_prot
+stack_expansion_ldst
+stack_expansion_signal
diff --git a/tools/testing/selftests/powerpc/mm/Makefile
b/tools/testing/selftests/powerpc/mm/Makefile
index 5a86d59441dc..6cd772e0e374 100644
--- a/tools/testing/selftests/powerpc/mm/Makefile
+++ b/tools/testing/selftests/powerpc/mm/Makefile
@@ -3,7 +3,9 @@
$(MAKE) -C ../
TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot segv_errors wild_bctr \
- large_vm_fork_separation bad_accesses pkey_exec_prot
+ large_vm_fork_separation bad_accesses pkey_exec_prot
stack_expansion_signal \
+ stack_expansion_ldst
+
TEST_GEN_PROGS_EXTENDED := tlbie_test
TEST_GEN_FILES := tempfile
@@ -17,6 +19,11 @@ $(OUTPUT)/large_vm_fork_separation: CFLAGS += -m64
$(OUTPUT)/bad_accesses: CFLAGS += -m64
$(OUTPUT)/pkey_exec_prot: CFLAGS += -m64
+$(OUTPUT)/stack_expansion_signal: ../utils.c ../pmu/lib.c
+
+$(OUTPUT)/stack_expansion_ldst: CFLAGS += -fno-stack-protector
+$(OUTPUT)/stack_expansion_ldst: ../utils.c
+
$(OUTPUT)/tempfile:
dd if=/dev/zero of=$@ bs=64k count=1
diff --git a/tools/testing/selftests/powerpc/mm/stack_expansion_ldst.c
b/tools/testing/selftests/powerpc/mm/stack_expansion_ldst.c
new file mode 100644
index ..0587e11437f5
--- /dev/null
+++ b/tools/testing/selftests/powerpc/mm/stack_expansion_ldst.c
@@ -0,0 +1,233 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test that loads/stores expand the stack segment, or trigger a SEGV, in
+ * various conditions.
+ *
+ * Based on test code by Tom Lane.
+ */
+
+#undef NDEBUG
+#include
+
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+
+#define _KB (1024)
+#define _MB (1024 * 1024)
+
+volatile char *stack_top_ptr;
+volatile unsigned long stack_top_sp;
+volatile char c;
+
+enum access_type {
+ LOAD,
+ STORE,
+};
+
+/*
+ * Consume stack until the stack pointer is below @target_sp, then do an access
+ * (load or store) at offset @delta from either the base of the stack or the
+ * current stack pointer.
+ */
+__attribute__ ((noinline))
+int consume_stack(unsigned long target_sp, unsigned long stack_high, int
delta, enum access_type type)
+{
+ unsigned long target;
+ char stack_cur;
+
+ if ((unsigned long)_cur > target_sp)
+ return consume_stack(target_sp, stack_high, delta, type);
+ else {
+ // We don't really need this, but without it GCC might not
+ // generate a recursive call above.
+ stack_top_ptr = _cur;
+
+#ifdef __powerpc__
+ asm volatile ("mr %[sp], %%r1" : [sp] "=r" (stack_top_sp));
+#else
+ asm volatile ("mov %%rsp, %[sp]" : [sp] "=r" (stack_top_sp));
+#endif
+
+ // Kludge, delta < 0 indicates relative to SP
+ if (delta < 0)
+ target = stack_top_sp + delta;
+ else
+ target = stack_high - delta + 1;
+
+ volatile char *p = (char *)target;
+
+ if (type == STORE)
+ *p = c;
+ else
+ c = *p;
+
+ // Do something to prevent the stack frame being popped prior to
+ // our access above.
+ getpid();
+ }
+
+ return 0;
+}
+
+static int search_proc_maps(char *needle, unsigned long *low, unsigned long
*high)
+{
+ unsigned long start, end;
+ static char buf[4096];
+ char
