Since we've changed div/mod exception handling for src_reg in
eBPF verifier itself, remove the leftovers from arm32 JIT.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Shubham Bansal <illusionist.neo@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Alexei Starovoitov says:

====================
pull-request: bpf-next 2018-01-19

The following pull-request contains BPF updates for your *net-next* tree.

The main changes are:

1) bpf array map HW offload, from Jakub.

2) support for bpf_get_next_key() for LPM map, from Yonghong.

3) test_verifier now runs loaded programs, from Alexei.

4) xdp cpumap monitoring, from Jesper.

5) variety of tests, cleanups and small x64 JIT optimization, from Daniel.

6) user space can now retrieve HW JITed program, from Jiong.

Note there is a minor conflict between Russell's arm32 JIT fixes
and removal of bpf_jit_enable variable by Daniel which should
be resolved by keeping Russell's comment and removing that variable.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

The BPF verifier conflict was some minor contextual issue.

The TUN conflict was less trivial.  Cong Wang fixed a memory leak of
tfile->tx_array in 'net'.  This is an skb_array.  But meanwhile in
net-next tun changed tfile->tx_arry into tfile->tx_ring which is a
ptr_ring.

Signed-off-by: David S. Miller <davem@davemloft.net>

Having a pure_initcall() callback just to permanently enable BPF
JITs under CONFIG_BPF_JIT_ALWAYS_ON is unnecessary and could leave
a small race window in future where JIT is still disabled on boot.
Since we know about the setting at compilation time anyway, just
initialize it properly there. Also consolidate all the individual
bpf_jit_enable variables into a single one and move them under one
location. Moreover, don't allow for setting unspecified garbage
values on them.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

As per 90caccdd8cc0 ("bpf: fix bpf_tail_call() x64 JIT"), the index used
for array lookup is defined to be 32-bit wide. Update a misleading
comment that suggests it is 64-bit wide.

Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

When the source and destination register are identical, our JIT does not
generate correct code, which leads to kernel oopses.

Fix this by (a) generating more efficient code, and (b) making use of
the temporary earlier if we will overwrite the address register.

Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

When an eBPF program tail-calls another eBPF program, it enters it after
the prologue to avoid having complex stack manipulations.  This can lead
to kernel oopses, and similar.

Resolve this by always using a fixed stack layout, a CPU register frame
pointer, and using this when reloading registers before returning.

Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

The stack layout documentation incorrectly suggests that the BPF JIT
scratch space starts immediately below BPF_FP. This is not correct,
so let's fix the documentation to reflect reality.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

Move the stack documentation towards the top of the file, where it's
relevant for things like the register layout.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

As per 2dede2d8e925 ("ARM EABI: stack pointer must be 64-bit aligned
after a CPU exception") the stack should be aligned to a 64-bit boundary
on EABI systems.  Ensure that the eBPF JIT appropraitely aligns the
stack.

Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>