[RFC v3 13/13] kprobes: port blacklist kprobes to linker table

Luis R. Rodriguez
2016-07-22T21:25:41Z

kprobe makes use of two sections, the one dealing with the actual
kprobes was recently ported using the standard section range API.
The blacklist functionality of kprobes is still using a custom
section and declaring its custom section using the linker script
as follows:

type Linux-section custom section name begin end
table .init.data _kprobe_blacklist __start_kprobe_blacklist __stop_kprobe_blacklist

This ports the _kprobe_blacklist custom section to the standard
Linux linker table API allowing us remove all the custom blacklist
kprobe section declarations from the linker script.

This has been tested by trying to register a kprobe on a blacklisted
symbol (these are declared with NOKPROBE_SYMBOL()), and confirms that
this fails to work as expected. This was tested with:

# insmod samples/kprobes/kprobe_example.ko symbol="get_kprobe"

This fails to load as expected with:

insmod: ERROR: could not insert module samples/kprobes/kprobe_example.ko: Invalid parameters

v3: this patch was introduced in this series

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
include/asm-generic/vmlinux.lds.h | 10 ----------
include/linux/kprobes.h | 5 +++--
kernel/kprobes.c | 11 ++++-------
3 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1664050e6560..0e4df8c61c18 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -113,15 +113,6 @@
#define BRANCH_PROFILE()
#endif

-#ifdef CONFIG_KPROBES
-#define KPROBE_BLACKLIST() . = ALIGN(8); \
- VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
- *(_kprobe_blacklist) \
- VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
-#else
-#define KPROBE_BLACKLIST()
-#endif
-
#ifdef CONFIG_EVENT_TRACING
#define FTRACE_EVENTS() . = ALIGN(8); \
VMLINUX_SYMBOL(__start_ftrace_events) = .; \
@@ -519,7 +510,6 @@
*(SECTION_INIT_RODATA) \
FTRACE_EVENTS() \
TRACE_SYSCALLS() \
- KPROBE_BLACKLIST() \
MEM_DISCARD(init.rodata) \
CLK_OF_TABLES() \
RESERVEDMEM_OF_TABLES() \
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 3f46b282a3f9..c9bb9caef70c 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -43,9 +43,11 @@

#ifdef CONFIG_KPROBES
#include <linux/ranges.h>
+#include <linux/tables.h>
#include <asm/kprobes.h>

DECLARE_SECTION_RANGE(kprobes);
+DECLARE_LINKTABLE(unsigned long, _kprobe_blacklist);

/* kprobe_status settings */
#define KPROBE_HIT_ACTIVE 0x00000001
@@ -490,8 +492,7 @@ static inline int enable_jprobe(struct jprobe *jp)
* by using this macro.
*/
#define __NOKPROBE_SYMBOL(fname) \
-static unsigned long __used \
- __attribute__((section("_kprobe_blacklist"))) \
+static LINKTABLE_INIT_DATA(_kprobe_blacklist, all) \
_kbl_addr_##fname = (unsigned long)fname;
#define NOKPROBE_SYMBOL(fname) __NOKPROBE_SYMBOL(fname)
#else
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 387605682622..4801aa3b4adf 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2053,14 +2053,13 @@ NOKPROBE_SYMBOL(dump_kprobe);
* since a kprobe need not necessarily be at the beginning
* of a function.
*/
-static int __init populate_kprobe_blacklist(unsigned long *start,
- unsigned long *end)
+static int __init populate_kprobe_blacklist(void)
{
unsigned long *iter;
struct kprobe_blacklist_entry *ent;
unsigned long entry, offset = 0, size = 0;

- for (iter = start; iter < end; iter++) {
+ LINKTABLE_FOR_EACH(iter, _kprobe_blacklist) {
entry = arch_deref_entry_point((void *)*iter);

if (!kernel_text_address(entry) ||
@@ -2125,8 +2124,7 @@ static struct notifier_block kprobe_module_nb = {
};

/* Markers of _kprobe_blacklist section */
-extern unsigned long __start_kprobe_blacklist[];
-extern unsigned long __stop_kprobe_blacklist[];
+DEFINE_LINKTABLE_INIT_DATA(unsigned long, _kprobe_blacklist);

/* Actual kprobes section range */
DEFINE_SECTION_RANGE(kprobes, SECTION_TEXT);
@@ -2143,8 +2141,7 @@ static int __init init_kprobes(void)
raw_spin_lock_init(&(kretprobe_table_locks[i].lock));
}

- err = populate_kprobe_blacklist(__start_kprobe_blacklist,
- __stop_kprobe_blacklist);
+ err = populate_kprobe_blacklist();
if (err) {
pr_err("kprobes: failed to populate blacklist: %d\n", err);
pr_err("Please take care of using kprobes.\n");
--
2.8.4