On 11/23/2018 10:41 AM, 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.biesheu...@linaro.org>
> ---
> kernel/bpf/core.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 1a796e0799ec..572dd74c26e3 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(const 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);
The const needs to be removed, this generates the following warning:
# make -j8 kernel/bpf/
DESCEND objtool
CALL scripts/checksyscalls.sh
CC kernel/bpf/core.o
CC kernel/bpf/syscall.o
CC kernel/bpf/verifier.o
CC kernel/bpf/hashtab.o
CC kernel/bpf/helpers.o
CC kernel/bpf/inode.o
CC kernel/bpf/arraymap.o
CC kernel/bpf/lpm_trie.o
kernel/bpf/core.c: In function ‘bpf_jit_free_exec’:
kernel/bpf/core.c:619:17: warning: passing argument 1 of ‘module_memfree’
discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
module_memfree(addr);
^~~~
In file included from kernel/bpf/core.c:28:0:
./include/linux/moduleloader.h:30:6: note: expected ‘void *’ but argument is of
type ‘const void *’
void module_memfree(void *module_region);
^~~~~~~~~~~~~~
CC kernel/bpf/local_storage.o
[...]
Please respin with that fixed.
Thanks,
Daniel
