Hi guys,
Please review the approach of using small fixed-sized arrays to improve
parsing of values like get_options() does.
This comes to me after fixing an overflow in get_options(). See the thread
for details: https://lkml.org/lkml/2017/5/22/581
If the approach is OK I’ll suggest to replace all of get_options() calls
to ksa_parse_ints() and remove get_options() at all.
Thank you.
Signed-off-by: Ilya V. Matveychikov <[email protected]>
---
include/linux/small_array.h | 35 +++++++++++++++++++++++++++++++++++
lib/Makefile | 2 +-
lib/cmdline.c | 4 +++-
lib/ksmall_array.c | 26 ++++++++++++++++++++++++++
4 files changed, 65 insertions(+), 2 deletions(-)
create mode 100644 include/linux/small_array.h
create mode 100644 lib/ksmall_array.c
diff --git a/include/linux/small_array.h b/include/linux/small_array.h
new file mode 100644
index 0000000..c5ccbe4d
--- /dev/null
+++ b/include/linux/small_array.h
@@ -0,0 +1,35 @@
+#ifndef __SMALL_ARRAY_H__
+#define __SMALL_ARRAY_H__
+
+/*
+ * Kingdom of Small Arrays (KSA)
+ */
+
+#include <linux/build_bug.h>
+
+#define KSA_S_BITS 8
+#define KSA_N_BITS 12
+
+struct ksmall_array {
+ unsigned int s : KSA_S_BITS; /* sizeof(item) */
+ unsigned int n : KSA_N_BITS; /* number of items stored */
+ unsigned int m : KSA_N_BITS; /* maximum number of items allowed */
+ unsigned char v[0];
+};
+
+#define KSA_DECLARE(name, type, count) \
+ struct { \
+ struct ksmall_array ksa; \
+ type data[count]; \
+ } name = {{ .s = sizeof(type), .n = 0, .m = count }}
+
+#define KSA(p) ((struct ksmall_array *)(p))
+#define KSA_S(p) KSA(p)->s
+#define KSA_N(p) KSA(p)->n
+#define KSA_M(p) KSA(p)->m
+#define KSA_V(p, t) ((t *)KSA(p)->v)
+#define KSA_GET(p, i, v) ((i < KSA_N(p)) ? (p)->data[i] : v)
+
+extern char *ksa_parse_ints(const char *str, struct ksmall_array *ksa);
+
+#endif /* __SMALL_ARRAY_H__ */
diff --git a/lib/Makefile b/lib/Makefile
index 40c1837..502f4b4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -30,7 +30,7 @@ lib-$(CONFIG_SMP) += cpumask.o
lib-$(CONFIG_DMA_NOOP_OPS) += dma-noop.o
lib-$(CONFIG_DMA_VIRT_OPS) += dma-virt.o
-lib-y += kobject.o klist.o
+lib-y += kobject.o klist.o ksmall_array.o
obj-y += lockref.o
obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
diff --git a/lib/cmdline.c b/lib/cmdline.c
index 4c0888c..233c4eb 100644
--- a/lib/cmdline.c
+++ b/lib/cmdline.c
@@ -63,8 +63,10 @@ int get_option(char **str, int *pint)
(*str)++;
return 2;
}
- if (**str == '-')
+ if (**str == '-') {
+ (*str)++;
return 3;
+ }
return 1;
}
diff --git a/lib/ksmall_array.c b/lib/ksmall_array.c
new file mode 100644
index 0000000..ecc8403
--- /dev/null
+++ b/lib/ksmall_array.c
@@ -0,0 +1,26 @@
+#include <linux/small_array.h>
+#include <linux/bug.h>
+
+char *ksa_parse_ints(const char *str, struct ksmall_array *ksa)
+{
+ int res, a, b;
+
+ BUG_ON(ksa->s != sizeof(int));
+
+ while (ksa->n < ksa->m) {
+ res = get_option((char **)&str, &a); b = a;
+ if (res == 0) break;
+ if (res == 3) res = get_option((char **)&str, &b);
+ if (res == 0) break;
+ while (a <= b && (ksa->n < ksa->m))
+ KSA_V(ksa, int)[ksa->n++] = a++;
+ }
+
+ return (char *)str;
+}
+EXPORT_SYMBOL(ksa_parse_ints);
+
+static void __attribute__((unused)) ksa_build_check(void)
+{
+ BUILD_BUG_ON(sizeof(struct ksmall_array) != sizeof(unsigned int));
+}
--
2.7.4
Signed-off-by: Ilya V. Matveychikov <[email protected]>
---
net/core/dev.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 8515f8f..acda9ac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -144,6 +144,7 @@
#include <linux/netfilter_ingress.h>
#include <linux/crash_dump.h>
#include <linux/sctp.h>
+#include <linux/small_array.h>
#include "net-sysfs.h"
@@ -645,23 +646,18 @@ unsigned long netdev_boot_base(const char *prefix, int unit)
*/
int __init netdev_boot_setup(char *str)
{
- int ints[5];
- struct ifmap map;
+ struct ifmap map = { 0 };
+ KSA_DECLARE(ints, int, 4);
- str = get_options(str, ARRAY_SIZE(ints), ints);
+ str = ksa_parse_ints(str, KSA(&ints));
if (!str || !*str)
return 0;
/* Save settings */
- memset(&map, 0, sizeof(map));
- if (ints[0] > 0)
- map.irq = ints[1];
- if (ints[0] > 1)
- map.base_addr = ints[2];
- if (ints[0] > 2)
- map.mem_start = ints[3];
- if (ints[0] > 3)
- map.mem_end = ints[4];
+ map.irq = KSA_GET(&ints, 0, 0);
+ map.base_addr = KSA_GET(&ints, 1, 0);
+ map.mem_start = KSA_GET(&ints, 2, 0);
+ map.mem_end = KSA_GET(&ints, 3, 0);
/* Add new entry to the list */
return netdev_boot_setup_add(str, &map);
--
2.7.4