mm: introduce execmem_alloc() and execmem_free()

module_alloc() is used everywhere as a mean to allocate memory for code.

Beside being semantically wrong, this unnecessarily ties all subsystems
that need to allocate code, such as ftrace, kprobes and BPF to modules and
puts the burden of code allocation to the modules code.

Several architectures override module_alloc() because of various
constraints where the executable memory can be located and this causes
additional obstacles for improvements of code allocation.

Start splitting code allocation from modules by introducing execmem_alloc()
and execmem_free() APIs.

Initially, execmem_alloc() is a wrapper for module_alloc() and
execmem_free() is a replacement of module_memfree() to allow updating all
call sites to use the new APIs.

Since architectures define different restrictions on placement,
permissions, alignment and other parameters for memory that can be used by
different subsystems that allocate executable memory, execmem_alloc() takes
a type argument, that will be used to identify the calling subsystem and to
allow architectures define parameters for ranges suitable for that
subsystem.

No functional changes.

Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

2 files changed, 5 insertions, 5 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 70139d9d2e01..c8ddb7abda7c 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -25,6 +25,7 @@
 #include <linux/memory.h>
 #include <linux/vmalloc.h>
 #include <linux/set_memory.h>
+#include <linux/execmem.h>
 
 #include <trace/syscall.h>
 
@@ -261,15 +262,14 @@ void arch_ftrace_update_code(int command)
 #ifdef CONFIG_X86_64
 
 #ifdef CONFIG_MODULES
-#include <linux/moduleloader.h>
 /* Module allocation simplifies allocating memory for code */
 static inline void *alloc_tramp(unsigned long size)
 {
-	return module_alloc(size);
+	return execmem_alloc(EXECMEM_FTRACE, size);
 }
 static inline void tramp_free(void *tramp)
 {
-	module_memfree(tramp);
+	execmem_free(tramp);
 }
 #else
 /* Trampolines can only be created if modules are supported */
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index d0e49bd7c6f3..72e6a45e7ec2 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -40,12 +40,12 @@
 #include <linux/kgdb.h>
 #include <linux/ftrace.h>
 #include <linux/kasan.h>
-#include <linux/moduleloader.h>
 #include <linux/objtool.h>
 #include <linux/vmalloc.h>
 #include <linux/pgtable.h>
 #include <linux/set_memory.h>
 #include <linux/cfi.h>
+#include <linux/execmem.h>
 
 #include <asm/text-patching.h>
 #include <asm/cacheflush.h>
@@ -495,7 +495,7 @@ void *alloc_insn_page(void)
 {
 	void *page;
 
-	page = module_alloc(PAGE_SIZE);
+	page = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
 	if (!page)
 		return NULL;