On Mon, Jan 27, 2025 at 01:50:31PM +0100, Petr Pavlu wrote:

On 1/26/25 08:47, Mike Rapoport wrote:

quoted

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Instead of using writable copy for module text sections, temporarily remap
the memory allocated from execmem's ROX cache as writable and restore its
ROX permissions after the module is formed.

This will allow removing nasty games with writable copy in alternatives
patching on x86.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

[...]

quoted

+static void module_memory_restore_rox(struct module *mod)
+{
+	for_class_mod_mem_type(type, text) {
+		struct module_memory *mem = &mod->mem[type];
+
+		if (mem->is_rox)
+			execmem_restore_rox(mem->base, mem->size);
+	}
+}
+

Can the execmem_restore_rox() call here fail? I realize that there isn't
much that the module loader can do if that happens, but should it be
perhaps logged as a warning?

It won't fail at this point. set_memory APIs may fail if they need to split
a large page and could not allocate a new page table, but here all the
splits were already done at module_memory_alloc() time.
 

-- 
Thanks,
Petr

-- 
Sincerely yours,
Mike.