On Fri, 30 Nov 2018 at 19:26, Will Deacon <will.dea...@arm.com> wrote: > > On Fri, Nov 23, 2018 at 11:18:04PM +0100, Ard Biesheuvel wrote: > > The arm64 module region is a 128 MB region that is kept close to > > the core kernel, in order to ensure that relative branches are > > always in range. So using the same region for programs that do > > not have this restriction is wasteful, and preferably avoided. > > > > Now that the core BPF JIT code permits the alloc/free routines to > > be overridden, implement them by vmalloc()/vfree() calls from a > > dedicated 128 MB region set aside for BPF programs. This ensures > > that BPF programs are still in branching range of each other, which > > is something the JIT currently depends upon (and is not guaranteed > > when using module_alloc() on KASLR kernels like we do currently). > > It also ensures that placement of BPF programs does not correlate > > with the placement of the core kernel or modules, making it less > > likely that leaking the former will reveal the latter. > > > > This also solves an issue under KASAN, where shadow memory is > > needlessly allocated for all BPF programs (which don't require KASAN > > shadow pages since they are not KASAN instrumented) > > > > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > > --- > > arch/arm64/include/asm/memory.h | 5 ++++- > > arch/arm64/net/bpf_jit_comp.c | 13 +++++++++++++ > > 2 files changed, 17 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/include/asm/memory.h > > b/arch/arm64/include/asm/memory.h > > index b96442960aea..ee20fc63899c 100644 > > --- a/arch/arm64/include/asm/memory.h > > +++ b/arch/arm64/include/asm/memory.h > > @@ -62,8 +62,11 @@ > > #define PAGE_OFFSET (UL(0xffffffffffffffff) - \ > > (UL(1) << (VA_BITS - 1)) + 1) > > #define KIMAGE_VADDR (MODULES_END) > > +#define BPF_JIT_REGION_START (VA_START + KASAN_SHADOW_SIZE) > > +#define BPF_JIT_REGION_SIZE (SZ_128M) > > +#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE) > > #define MODULES_END (MODULES_VADDR + MODULES_VSIZE) > > -#define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE) > > +#define MODULES_VADDR (BPF_JIT_REGION_END) > > #define MODULES_VSIZE (SZ_128M) > > #define VMEMMAP_START (PAGE_OFFSET - VMEMMAP_SIZE) > > #define PCI_IO_END (VMEMMAP_START - SZ_2M) > > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > > index a6fdaea07c63..76c2ab40c02d 100644 > > --- a/arch/arm64/net/bpf_jit_comp.c > > +++ b/arch/arm64/net/bpf_jit_comp.c > > @@ -940,3 +940,16 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog > > *prog) > > tmp : orig_prog); > > return prog; > > } > > + > > +void *bpf_jit_alloc_exec(unsigned long size) > > +{ > > + return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START, > > + BPF_JIT_REGION_END, GFP_KERNEL, > > + PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, > > + __builtin_return_address(0)); > > I guess we'll want VM_IMMEDIATE_UNMAP here if Rich gets that merged.
I think akpm already queued up that patch. > In the > meantime, I wonder if it's worth zeroing the region in bpf_jit_free_exec()? > (although we'd need the size information...). > Not sure. What exactly would that achieve?