Le 16/03/2021 à 04:17, Jordan Niethe a écrit :
From: Russell Currey <rus...@russell.cc>
With CONFIG_STRICT_KERNEL_RWX=y and CONFIG_KPROBES=y, there will be one
W+X page at boot by default. This can be tested with
CONFIG_PPC_PTDUMP=y and CONFIG_PPC_DEBUG_WX=y set, and checking the
kernel log during boot.
This text is confusing. I don't understand what is the status before the patch, and what is the
status after.
"there will be one ...", does it mean after the patch ?
Add an arch specific insn page allocator which returns RO pages if
STRICT_KERNEL_RWX is enabled. This page is only written to with
patch_instruction() which is able to write RO pages.
"an" or "the" arch specific insn page allocator ?
Reviewed-by: Daniel Axtens <d...@axtens.net>
Signed-off-by: Russell Currey <rus...@russell.cc>
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
[jpn: Reword commit message, switch from vmalloc_exec(), add
free_insn_page()]
Signed-off-by: Jordan Niethe <jniet...@gmail.com>
---
v9: - vmalloc_exec() no longer exists
- Set the page to RW before freeing it
---
arch/powerpc/kernel/kprobes.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 01ab2163659e..bb7e4d321988 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -25,6 +25,8 @@
#include <asm/sections.h>
#include <asm/inst.h>
#include <linux/uaccess.h>
+#include <linux/set_memory.h>
+#include <linux/vmalloc.h>
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -103,6 +105,26 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name,
unsigned int offset)
return addr;
}
+void *alloc_insn_page(void)
+{
+ void *page = vmalloc(PAGE_SIZE);
Can't do that on book3s/32, see https://github.com/linuxppc/linux/commit/6ca05532 and
https://github.com/linuxppc/linux/commit/7fbc22ce
Should do:
return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
GFP_KERNEL,
PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
NUMA_NO_NODE,
__builtin_return_address(0));
To keep it simple, you'll probably need to define MODULES_VADDR and MODULES_END as resp
VMALLOC_START and VMALLOC_END when they are not defined, maybe in asm/pgtable.h
+
+ if (!page)
+ return NULL;
+
+ set_memory_ro((unsigned long)page, 1);
+ set_memory_x((unsigned long)page, 1);
+
+ return page;
+}
+
+void free_insn_page(void *page)
+{
+ set_memory_nx((unsigned long)page, 1);
+ set_memory_rw((unsigned long)page, 1);
+ vfree(page);
+}
+
int arch_prepare_kprobe(struct kprobe *p)
{
int ret = 0;
