On Thu, Jun 18, 2020 at 10:55:58AM +0200, David Hildenbrand wrote:

On 18.06.20 08:43, Christoph Hellwig wrote:

quoted

Use PAGE_KERNEL_ROX directly instead of allocating RWX and setting the
page read-only just after the allocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm64/kernel/probes/kprobes.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d1c95dcf1d7833..cbe49cd117cfec 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c

@@ -120,15 +120,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 
 void *alloc_insn_page(void)
 {
-	void *page;
-
-	page = vmalloc_exec(PAGE_SIZE);
-	if (page) {
-		set_memory_ro((unsigned long)page, 1);
-		set_vm_flush_reset_perms(page);
-	}
-
-	return page;
+	return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
+			GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
+			NUMA_NO_NODE, __func__);

I do wonder if something like vmalloc_prot(size, prot) would make this
(and the other two users) easier to read.

So instead of ripping out vmalloc_exec(), converting it into
vmalloc_prot() instead.

Did you consider that?

For x86 Christoph did module_alloc_prot(), which is in his more
extensive set of patches addressing this. I suspect that would be the
right thing for ARM64 as well.