[PATCH v11 4/9] powerpc/kprobes: Mark newly allocated probes as ROX

[Jordan Niethe <jniethe5@gmail.com>]

From: Russell Currey <ruscur@russell.cc>

Add the arch specific insn page allocator for powerpc. This allocates
ROX pages if STRICT_KERNEL_RWX is enabled. These pages are only written
to with patch_instruction() which is able to write RO pages.

Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[jpn: Reword commit message, switch to __vmalloc_node_range()]
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
v9: - vmalloc_exec() no longer exists
    - Set the page to RW before freeing it
v10: - use __vmalloc_node_range()
v11: - Neaten up
---
 arch/powerpc/kernel/kprobes.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 01ab2163659e..5670b43e254f 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -25,6 +25,7 @@
 #include <asm/sections.h>
 #include <asm/inst.h>
 #include <linux/uaccess.h>
+#include <linux/vmalloc.h>
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -103,6 +104,16 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 	return addr;
 }
 
+void *alloc_insn_page(void)
+{
+	pgprot_t prot = IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ? PAGE_KERNEL_ROX :
+							       PAGE_KERNEL_EXEC;
+
+	return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
+			GFP_KERNEL, prot, VM_FLUSH_RESET_PERMS,
+			NUMA_NO_NODE, __builtin_return_address(0));
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
-- 
2.25.1