[PATCH bpf-next v3 4/5] error-injection: Add injectable error types

From: Masami Hiramatsu
Date: Wed Jan 10 2018 - 05:19:08 EST

Add injectable error types for each error-injectable function.

One motivation of error injection test is to find software flaws,
mistakes or mis-handlings of expectable errors. If we find such
flaws by the test, that is a program bug, so we need to fix it.

But if the tester miss input the error (e.g. just return success
code without processing anything), it causes unexpected behavior
even if the caller is correctly programmed to handle any errors.
That is not what we want to test by error injection.

To clarify what type of errors the caller must expect for each
injectable function, this introduces injectable error types:

- EI_ETYPE_NULL : means the function will return NULL if it
fails. No ERR_PTR, just a NULL.
- EI_ETYPE_ERRNO : means the function will return -ERRNO
if it fails.
- EI_ETYPE_ERRNO_NULL : means the function will return -ERRNO
(ERR_PTR) or NULL.

ALLOW_ERROR_INJECTION() macro is expanded to get one of
NULL, ERRNO, ERRNO_NULL to record the error type for
each function. e.g.

ALLOW_ERROR_INJECTION(open_ctree, ERRNO)

This error types are shown in debugfs as below.

====
/ # cat /sys/kernel/debug/error_injection/list
open_ctree [btrfs] ERRNO
io_ctl_init [btrfs] ERRNO
====

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
fs/btrfs/disk-io.c | 2 +-
fs/btrfs/free-space-cache.c | 2 +-
include/asm-generic/error-injection.h | 23 +++++++++++++++---
include/asm-generic/vmlinux.lds.h | 2 +-
include/linux/error-injection.h | 6 +++++
include/linux/module.h | 3 ++
lib/error-inject.c | 43 ++++++++++++++++++++++++++++-----
7 files changed, 66 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5c540129ad81..9269fc23f490 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3124,7 +3124,7 @@ int open_ctree(struct super_block *sb,
goto fail_block_groups;
goto retry_root_backup;
}
-ALLOW_ERROR_INJECTION(open_ctree);
+ALLOW_ERROR_INJECTION(open_ctree, ERRNO);

static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 2a75e088b215..9eb45f77e381 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -333,7 +333,7 @@ static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct inode *inode,

return 0;
}
-ALLOW_ERROR_INJECTION(io_ctl_init);
+ALLOW_ERROR_INJECTION(io_ctl_init, ERRNO);

static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
{
diff --git a/include/asm-generic/error-injection.h b/include/asm-generic/error-injection.h
index 08352c9d9f97..296c65442f00 100644
--- a/include/asm-generic/error-injection.h
+++ b/include/asm-generic/error-injection.h
@@ -3,17 +3,32 @@
#define _ASM_GENERIC_ERROR_INJECTION_H

#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
+enum {
+ EI_ETYPE_NONE, /* Dummy value for undefined case */
+ EI_ETYPE_NULL, /* Return NULL if failure */
+ EI_ETYPE_ERRNO, /* Return -ERRNO if failure */
+ EI_ETYPE_ERRNO_NULL, /* Return -ERRNO or NULL if failure */
+};
+
+struct error_injection_entry {
+ unsigned long addr;
+ int etype;
+};
+
#ifdef CONFIG_FUNCTION_ERROR_INJECTION
/*
* Whitelist ganerating macro. Specify functions which can be
* error-injectable using this macro.
*/
-#define ALLOW_ERROR_INJECTION(fname) \
-static unsigned long __used \
+#define ALLOW_ERROR_INJECTION(fname, _etype) \
+static struct error_injection_entry __used \
__attribute__((__section__("_error_injection_whitelist"))) \
- _eil_addr_##fname = (unsigned long)fname;
+ _eil_addr_##fname = { \
+ .addr = (unsigned long)fname, \
+ .etype = EI_ETYPE_##_etype, \
+ };
#else
-#define ALLOW_ERROR_INJECTION(fname)
+#define ALLOW_ERROR_INJECTION(fname, _etype)
#endif
#endif

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f2068cca5206..ebe544e048cd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -137,7 +137,7 @@
#endif

#ifdef CONFIG_FUNCTION_ERROR_INJECTION
-#define ERROR_INJECT_WHITELIST() . = ALIGN(8); \
+#define ERROR_INJECT_WHITELIST() STRUCT_ALIGN(); \
VMLINUX_SYMBOL(__start_error_injection_whitelist) = .;\
KEEP(*(_error_injection_whitelist)) \
VMLINUX_SYMBOL(__stop_error_injection_whitelist) = .;
diff --git a/include/linux/error-injection.h b/include/linux/error-injection.h
index 130a67c50dac..280c61ecbf20 100644
--- a/include/linux/error-injection.h
+++ b/include/linux/error-injection.h
@@ -7,6 +7,7 @@
#include <asm/error-injection.h>

extern bool within_error_injection_list(unsigned long addr);
+extern int get_injectable_error_type(unsigned long addr);

#else /* !CONFIG_FUNCTION_ERROR_INJECTION */

@@ -16,6 +17,11 @@ static inline bool within_error_injection_list(unsigned long addr)
return false;
}

+static inline int get_injectable_error_type(unsigned long addr)
+{
+ return EI_ETYPE_NONE;
+}
+
#endif

#endif /* _LINUX_ERROR_INJECTION_H */
diff --git a/include/linux/module.h b/include/linux/module.h
index 792e51d83bda..9642d3116718 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -19,6 +19,7 @@
#include <linux/jump_label.h>
#include <linux/export.h>
#include <linux/rbtree_latch.h>
+#include <linux/error-injection.h>

#include <linux/percpu.h>
#include <asm/module.h>
@@ -477,8 +478,8 @@ struct module {
#endif

#ifdef CONFIG_FUNCTION_ERROR_INJECTION
+ struct error_injection_entry *ei_funcs;
unsigned int num_ei_funcs;
- unsigned long *ei_funcs;
#endif
} ____cacheline_aligned __randomize_layout;
#ifndef MODULE_ARCH_INIT
diff --git a/lib/error-inject.c b/lib/error-inject.c
index ac9a371af719..1c303881ba5c 100644
--- a/lib/error-inject.c
+++ b/lib/error-inject.c
@@ -16,6 +16,7 @@ struct ei_entry {
struct list_head list;
unsigned long start_addr;
unsigned long end_addr;
+ int etype;
void *priv;
};

@@ -35,6 +36,17 @@ bool within_error_injection_list(unsigned long addr)
return false;
}

+int get_injectable_error_type(unsigned long addr)
+{
+ struct ei_entry *ent;
+
+ list_for_each_entry(ent, &error_injection_list, list) {
+ if (addr >= ent->start_addr && addr < ent->end_addr)
+ return ent->etype;
+ }
+ return EI_ETYPE_NONE;
+}
+
/*
* Lookup and populate the error_injection_list.
*
@@ -42,16 +54,17 @@ bool within_error_injection_list(unsigned long addr)
* bpf_error_injection, so we need to populate the list of the symbols that have
* been marked as safe for overriding.
*/
-static void populate_error_injection_list(unsigned long *start,
- unsigned long *end, void *priv)
+static void populate_error_injection_list(struct error_injection_entry *start,
+ struct error_injection_entry *end,
+ void *priv)
{
- unsigned long *iter;
+ struct error_injection_entry *iter;
struct ei_entry *ent;
unsigned long entry, offset = 0, size = 0;

mutex_lock(&ei_mutex);
for (iter = start; iter < end; iter++) {
- entry = arch_deref_entry_point((void *)*iter);
+ entry = arch_deref_entry_point((void *)iter->addr);

if (!kernel_text_address(entry) ||
!kallsyms_lookup_size_offset(entry, &size, &offset)) {
@@ -65,6 +78,7 @@ static void populate_error_injection_list(unsigned long *start,
break;
ent->start_addr = entry;
ent->end_addr = entry + size;
+ ent->etype = iter->etype;
ent->priv = priv;
INIT_LIST_HEAD(&ent->list);
list_add_tail(&ent->list, &error_injection_list);
@@ -73,8 +87,8 @@ static void populate_error_injection_list(unsigned long *start,
}

/* Markers of the _error_inject_whitelist section */
-extern unsigned long __start_error_injection_whitelist[];
-extern unsigned long __stop_error_injection_whitelist[];
+extern struct error_injection_entry __start_error_injection_whitelist[];
+extern struct error_injection_entry __stop_error_injection_whitelist[];

static void __init populate_kernel_ei_list(void)
{
@@ -157,11 +171,26 @@ static void *ei_seq_next(struct seq_file *m, void *v, loff_t *pos)
return seq_list_next(v, &error_injection_list, pos);
}

+static const char *error_type_string(int etype)
+{
+ switch (etype) {
+ case EI_ETYPE_NULL:
+ return "NULL";
+ case EI_ETYPE_ERRNO:
+ return "ERRNO";
+ case EI_ETYPE_ERRNO_NULL:
+ return "ERRNO_NULL";
+ default:
+ return "(unknown)";
+ }
+}
+
static int ei_seq_show(struct seq_file *m, void *v)
{
struct ei_entry *ent = list_entry(v, struct ei_entry, list);

- seq_printf(m, "%pf\n", (void *)ent->start_addr);
+ seq_printf(m, "%pf\t%s\n", (void *)ent->start_addr,
+ error_type_string(ent->etype));
return 0;
}