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Subject[PATCH v3 1/2] bpf: add __weak hook for allocating executable memory
Date
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(-)

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);
}

--
2.17.1
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