| Message ID | 20181123221804.440-2-ard.biesheuvel@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v4,1/2] bpf: add __weak hook for allocating executable memory | expand |
On Fri, 2018-11-23 at 23:18 +0100, Ard Biesheuvel wrote: > 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> > --- It looks like some of the architectures call module_alloc directly in their bpf_jit_compile implementations as well. Rick
On Mon, Nov 26, 2018 at 9:02 AM Edgecombe, Rick P <rick.p.edgecombe@intel.com> wrote: > > On Fri, 2018-11-23 at 23:18 +0100, Ard Biesheuvel wrote: > > 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> > > --- > > It looks like some of the architectures call module_alloc directly in their > bpf_jit_compile implementations as well. Ew, good catch. :P -- Kees Cook
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 1a796e0799ec..78e9b76201b3 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -609,6 +609,16 @@ 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, @@ -626,7 +636,7 @@ 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; @@ -650,7 +660,7 @@ 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); }
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> --- kernel/bpf/core.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) -- 2.19.1