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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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