[PATCH -tip ] [BUGFIX] kprobes: Move hash_64() into .text.kprobesection

[Masami Hiramatsu]

Beacuse hash_64() is called from the get_kprobe() inside
int3 handler, kernel causes int3 recursion and crashes if
kprobes user puts a probe on it.

Usually hash_64() is inlined into caller function, but in
some cases, it has instances by gcc's interprocedural
constant propagation.

This patch adds __kprobes tag on the hash_64() and moves
all those instances into .text.kprobe section so that
kprobes can refuse probing on the instances.

I've ensured that all hash_64 instances moves to the
address between __kprobes_text_start and __kprobes_text_end
with this patch as below.

ffffffff8138bea0 T __kprobes_text_start
ffffffff8138bec0 t hash_64.constprop.8
ffffffff8138ef98 t hash_64.constprop.26
ffffffff8138efae t hash_64
ffffffff8138f066 t hash_64.constprop.43
ffffffff8138f649 t hash_64.constprop.25
ffffffff8139103a t hash_64.constprop.77
ffffffff81391050 t hash_64.constprop.24
ffffffff81391066 t hash_64.constprop.40
ffffffff8139107c t hash_64.constprop.15
ffffffff81391092 T __kprobes_text_end

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Reported-by: Timo Juhani Lindfors <timo.lindfors@xxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Nadia Yvette Chambers <nyc@xxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
---
 include/linux/hash.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/hash.h b/include/linux/hash.h
index 61c97ae..d83f62f 100644
--- a/include/linux/hash.h
+++ b/include/linux/hash.h
@@ -15,6 +15,7 @@
  */
 
 #include <asm/types.h>
+#include <linux/kprobes.h>
 
 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
 #define GOLDEN_RATIO_PRIME_32 0x9e370001UL
@@ -31,7 +32,7 @@
 #error Wordsize not 32 or 64
 #endif
 
-static inline u64 hash_64(u64 val, unsigned int bits)
+static __kprobes inline u64 hash_64(u64 val, unsigned int bits)
 {
 	u64 hash = val;
 

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