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Subject[patch 8/8] stacktrace filtering for fault-injection capabilities
This patch provides stacktrace filtering feature.
The stacktrace filter allows failing only for the caller you are
interested in.

stacktrace filter is enabled by setting the value of
/debugfs/*/stacktrace-depth more than 0.
and specify the range of the virtual address
by the /debugfs/*/address-start and /debugfs/*/address-end
Please see the example that demostrates how to inject slab allocation
failures only for a specific module
in Documentation/fault-injection/fault-injection.txt

Cc: Valdis.Kletnieks@vt.edu
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>

include/linux/fault-inject.h | 15 +++++++++
lib/Kconfig.debug | 2 +
lib/fault-inject-debugfs.c | 32 +++++++++++++++++++
lib/fault-inject.c | 71 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 120 insertions(+)
Index: work-shouldfail/lib/fault-inject.c
===================================================================
--- work-shouldfail.orig/lib/fault-inject.c
+++ work-shouldfail/lib/fault-inject.c
@@ -6,6 +6,9 @@
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/interrupt.h>
+#include <linux/unwind.h>
+#include <linux/stacktrace.h>
+#include <linux/kallsyms.h>
#include <linux/fault-inject.h>

int setup_fault_attr(struct fault_attr *attr, char *str)
@@ -59,6 +62,72 @@ static int fail_process(struct fault_att
return !in_interrupt() && task->make_it_fail;
}

+#ifdef CONFIG_STACK_UNWIND
+
+static asmlinkage int fail_stacktrace_callback(struct unwind_frame_info *info,
+ void *arg)
+{
+ int depth;
+ struct fault_attr *attr = arg;
+
+ for (depth = 0; depth < attr->stacktrace_depth
+ && unwind(info) == 0 && UNW_PC(info); depth++) {
+ if (arch_unw_user_mode(info))
+ break;
+ if (attr->address_start <= UNW_PC(info) &&
+ UNW_PC(info) < attr->address_end)
+ return 1;
+ }
+ return 0;
+}
+
+static int fail_stacktrace(struct fault_attr *attr)
+{
+ struct unwind_frame_info info;
+
+ /* stacktrace filter is disabled */
+ if (attr->stacktrace_depth == 0)
+ return 1;
+
+ return unwind_init_running(&info, fail_stacktrace_callback, attr);
+}
+
+#elif defined(CONFIG_STACKTRACE)
+
+#include <linux/stacktrace.h>
+
+#define MAX_STACK_TRACE_DEPTH 10
+
+static int fail_stacktrace(struct fault_attr *attr)
+{
+ struct stack_trace trace;
+ int depth = attr->stacktrace_depth;
+ unsigned long entries[MAX_STACK_TRACE_DEPTH];
+ int n;
+
+ /* stacktrace filter is disabled */
+ if (depth == 0)
+ return 1;
+
+ trace.nr_entries = 0;
+ trace.entries = entries;
+ trace.max_entries = (depth < MAX_STACK_TRACE_DEPTH) ?
+ depth : MAX_STACK_TRACE_DEPTH;
+
+ save_stack_trace(&trace, NULL, 0, 1);
+ for (n = 0; n < trace.nr_entries; n++)
+ if (attr->address_start <= entries[n] &&
+ entries[n] < attr->address_end)
+ return 1;
+ return 0;
+}
+
+#else
+
+#define fail_stacktrace(attr) (0)
+
+#endif
+
/*
* This code is stolen from failmalloc-1.0
* http://www.nongnu.org/failmalloc/
@@ -68,6 +137,8 @@ int should_fail(struct fault_attr *attr,
{
if (!fail_process(attr, current))
return 0;
+ if (!fail_stacktrace(attr))
+ return 0;

if (atomic_read(&max_failures(attr)) == 0)
return 0;
Index: work-shouldfail/include/linux/fault-inject.h
===================================================================
--- work-shouldfail.orig/include/linux/fault-inject.h
+++ work-shouldfail/include/linux/fault-inject.h
@@ -30,6 +30,21 @@ struct fault_attr {

/* A value of '0' means process filter is disabled. */
u32 process_filter;
+
+ /*
+ * maximam number of stacktrace depth walking allowed
+ * A value of '0' means stacktrace filter is disabled.
+ */
+ unsigned long stacktrace_depth;
+
+ /*
+ * If stacktrace_depth is enabled, it allows failing only when it
+ * has been called from the virtual addresses in the range
+ * 'address_start' to 'address_end-1'
+ */
+ unsigned long address_start;
+ unsigned long address_end;
+
};

#define DEFINE_FAULT_ATTR(name) \
Index: work-shouldfail/lib/fault-inject-debugfs.c
===================================================================
--- work-shouldfail.orig/lib/fault-inject-debugfs.c
+++ work-shouldfail/lib/fault-inject-debugfs.c
@@ -9,6 +9,9 @@ struct fault_attr_entries {
struct dentry *times_file;
struct dentry *space_file;
struct dentry *process_filter_file;
+ struct dentry *stacktrace_depth_file;
+ struct dentry *address_start_file;
+ struct dentry *address_end_file;
};

static void debugfs_ul_set(void *data, u64 val)
@@ -71,6 +74,18 @@ static void cleanup_fault_attr_entries(s
debugfs_remove(entries->process_filter_file);
entries->process_filter_file = NULL;
}
+ if (entries->stacktrace_depth_file) {
+ debugfs_remove(entries->stacktrace_depth_file);
+ entries->stacktrace_depth_file = NULL;
+ }
+ if (entries->address_start_file) {
+ debugfs_remove(entries->address_start_file);
+ entries->address_start_file = NULL;
+ }
+ if (entries->address_end_file) {
+ debugfs_remove(entries->address_end_file);
+ entries->address_end_file = NULL;
+ }
debugfs_remove(entries->dir);
entries->dir = NULL;
}
@@ -116,6 +131,23 @@ static int init_fault_attr_entries(struc
goto fail;
entries->process_filter_file = file;

+ file = debugfs_create_ul("stacktrace-depth", mode, dir,
+ &attr->stacktrace_depth);
+ if (!file)
+ goto fail;
+ entries->stacktrace_depth_file = file;
+
+ file = debugfs_create_ul("address-start", mode, dir,
+ &attr->address_start);
+ if (!file)
+ goto fail;
+ entries->address_start_file = file;
+
+ file = debugfs_create_ul("address-end", mode, dir, &attr->address_end);
+ if (!file)
+ goto fail;
+ entries->address_end_file = file;
+
return 0;
fail:
cleanup_fault_attr_entries(entries);
Index: work-shouldfail/lib/Kconfig.debug
===================================================================
--- work-shouldfail.orig/lib/Kconfig.debug
+++ work-shouldfail/lib/Kconfig.debug
@@ -371,6 +371,8 @@ config RCU_TORTURE_TEST

config FAULT_INJECTION
bool
+ select STACKTRACE
+ select FRAME_POINTER

config FAILSLAB
bool "fault-injection capabilitiy for kmalloc"
--
-
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