execmem: introduce execmem_alloc_rw()

Some callers of execmem_alloc() require the memory to be temporarily
writable even when it is allocated from ROX cache.  These callers use
execemem_make_temp_rw() right after the call to execmem_alloc().

Wrap this sequence in execmem_alloc_rw() API.

Link: https://lkml.kernel.org/r/20250713071730.4117334-3-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Daniel Gomez <da.gomez@samsung.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 22 insertions, 16 deletions

diff --git a/include/linux/execmem.h b/include/linux/execmem.h
index 734fbe83d98e..8b61b05da7d5 100644
--- a/include/linux/execmem.h
+++ b/include/linux/execmem.h
@@ -68,21 +68,6 @@ enum execmem_range_flags {
 void execmem_fill_trapping_insns(void *ptr, size_t size, bool writable);
 
 /**
- * execmem_make_temp_rw - temporarily remap region with read-write
- *			  permissions
- * @ptr:	address of the region to remap
- * @size:	size of the region to remap
- *
- * Remaps a part of the cached large page in the ROX cache in the range
- * [@ptr, @ptr + @size) as writable and not executable. The caller must
- * have exclusive ownership of this range and ensure nothing will try to
- * execute code in this range.
- *
- * Return: 0 on success or negative error code on failure.
- */
-int execmem_make_temp_rw(void *ptr, size_t size);
-
-/**
  * execmem_restore_rox - restore read-only-execute permissions
  * @ptr:	address of the region to remap
  * @size:	size of the region to remap
@@ -95,7 +80,6 @@ int execmem_make_temp_rw(void *ptr, size_t size);
  */
 int execmem_restore_rox(void *ptr, size_t size);
 #else
-static inline int execmem_make_temp_rw(void *ptr, size_t size) { return 0; }
 static inline int execmem_restore_rox(void *ptr, size_t size) { return 0; }
 #endif
 
@@ -166,6 +150,28 @@ struct execmem_info *execmem_arch_setup(void);
 void *execmem_alloc(enum execmem_type type, size_t size);
 
 /**
+ * execmem_alloc_rw - allocate writable executable memory
+ * @type: type of the allocation
+ * @size: how many bytes of memory are required
+ *
+ * Allocates memory that will contain executable code, either generated or
+ * loaded from kernel modules.
+ *
+ * Allocates memory that will contain data coupled with executable code,
+ * like data sections in kernel modules.
+ *
+ * Forces writable permissions on the allocated memory and the caller is
+ * responsible to manage the permissions afterwards.
+ *
+ * For architectures that use ROX cache the permissions will be set to R+W.
+ * For architectures that don't use ROX cache the default permissions for @type
+ * will be used as they must be writable.
+ *
+ * Return: a pointer to the allocated memory or %NULL
+ */
+void *execmem_alloc_rw(enum execmem_type type, size_t size);
+
+/**
  * execmem_free - free executable memory
  * @ptr: pointer to the memory that should be freed
  */