[RFC PATCH 2/4] powerpc: kprobe: add arch specific blacklist

[Naveen N. Rao]

Add symbol to mark end of entry_*.S and use the same to blacklist all
addresses from kernel start (_stext) to entry code from kprobes. Much of
this code is early exception handling where we can't really take a trap.

Reported-by: Anton Blanchard <anton at samba.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
---
 arch/powerpc/kernel/entry_32.S |  2 ++
 arch/powerpc/kernel/entry_64.S |  2 ++
 arch/powerpc/kernel/kprobes.c  | 10 ++++++++++
 3 files changed, 14 insertions(+)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3841d74..de1ed6e 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -1410,3 +1410,5 @@ _GLOBAL(return_to_handler)
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
 #endif /* CONFIG_FUNCTION_TRACER */
+
+_GLOBAL_SYM(__entry_text_end)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 6432d4b..f5f99920 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1551,3 +1551,5 @@ _GLOBAL(return_to_handler)
 	blr
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 #endif /* CONFIG_FUNCTION_TRACER */
+
+_GLOBAL_SYM(__entry_text_end)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 9479d8e..b5173d6 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -36,12 +36,22 @@
 #include <asm/cacheflush.h>
 #include <asm/sstep.h>
 #include <asm/uaccess.h>
+#include <asm/sections.h>
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
 
+bool arch_within_kprobe_blacklist(unsigned long addr)
+{
+	/* The __kprobes marked functions and entry code must not be probed */
+	return (addr >= (unsigned long)__kprobes_text_start &&
+	        addr < (unsigned long)__kprobes_text_end) ||
+	       (addr >= (unsigned long)_stext &&
+		addr < (unsigned long)__entry_text_end);
+}
+
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
-- 
2.10.2