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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>
This commit is contained in:
Ard Biesheuvel 2018-11-23 23:18:03 +01:00 committed by Daniel Borkmann
parent 2a95471c33
commit dc002bb62f
1 changed files with 12 additions and 2 deletions
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14
kernel/bpf/core.c
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@ -623,6 +623,16 @@ static void bpf_jit_uncharge_modmem(u32 pages)
atomic_long_sub(pages, &bpf_jit_current); 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 * struct bpf_binary_header *
bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr, bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
unsigned int alignment, unsigned int alignment,
@ -640,7 +650,7 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
if (bpf_jit_charge_modmem(pages)) if (bpf_jit_charge_modmem(pages))
return NULL; return NULL;
hdr = module_alloc(size); hdr = bpf_jit_alloc_exec(size);
if (!hdr) { if (!hdr) {
bpf_jit_uncharge_modmem(pages); bpf_jit_uncharge_modmem(pages);
return NULL; return NULL;
@ -664,7 +674,7 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
{ {
u32 pages = hdr->pages; u32 pages = hdr->pages;
module_memfree(hdr); bpf_jit_free_exec(hdr);
bpf_jit_uncharge_modmem(pages); bpf_jit_uncharge_modmem(pages);
} }