Re: [PATCH v10 04/10] powerpc/kprobes: Mark newly allocated probes as ROX

On Tue, Mar 30, 2021 at 4:05 PM Christophe Leroy
[off-list ref] wrote:

Le 30/03/2021 à 06:51, Jordan Niethe a écrit :

quoted

From: Russell Currey <redacted>

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 <redacted>
Signed-off-by: Russell Currey <redacted>
Signed-off-by: Christophe Leroy <redacted>
[jpn: Reword commit message, switch to __vmalloc_node_range()]
Signed-off-by: Jordan Niethe <redacted>
---
v9: - vmalloc_exec() no longer exists
     - Set the page to RW before freeing it
v10: - use __vmalloc_node_range()
---
  arch/powerpc/kernel/kprobes.c | 14 ++++++++++++++
  1 file changed, 14 insertions(+)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 01ab2163659e..3ae27af9b094 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 +104,19 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
      return addr;
  }

+void *alloc_insn_page(void)
+{
+     if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
+             return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
+                             GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
+                             NUMA_NO_NODE, __builtin_return_address(0));
+     } else {
+             return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
+                             GFP_KERNEL, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
+                             NUMA_NO_NODE, __builtin_return_address(0));
+     }
+}
+

What about

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));
}

Yes, that is better.

quoted

  int arch_prepare_kprobe(struct kprobe *p)
  {
      int ret = 0;