bpf: add __weak hook for allocating executable memory

By default, BPF uses module_alloc() to allocate executable memory,
but this is not necessary on all arches and potentially undesirable
on some of them.

So break out the module_alloc() and module_memfree() calls into __weak
functions to allow them to be overridden in arch code.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index f93ed66..86817ab 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -623,6 +623,16 @@ static void bpf_jit_uncharge_modmem(u32 pages)
        atomic_long_sub(pages, &bpf_jit_current);
 }
 
+void *__weak bpf_jit_alloc_exec(unsigned long size)
+{
+       return module_alloc(size);
+}
+
+void __weak bpf_jit_free_exec(void *addr)
+{
+       module_memfree(addr);
+}
+
 struct bpf_binary_header *
 bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
                     unsigned int alignment,
@@ -640,7 +650,7 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
 
        if (bpf_jit_charge_modmem(pages))
                return NULL;
-       hdr = module_alloc(size);
+       hdr = bpf_jit_alloc_exec(size);
        if (!hdr) {
                bpf_jit_uncharge_modmem(pages);
                return NULL;
@@ -664,7 +674,7 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
        u32 pages = hdr->pages;
 
-       module_memfree(hdr);
+       bpf_jit_free_exec(hdr);
        bpf_jit_uncharge_modmem(pages);
 }