diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2024-03-07 17:08:02 -0800 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2024-03-11 15:37:24 -0700 |
| commit | 142fd4d2dcf58b1720a6af644f31de1a5551f219 (patch) | |
| tree | aefa22cd078872844283df5ae8aa9f64e1614fa9 /kernel/bpf | |
| parent | 2fe99eb0ccf2bb73df65ebcbbf2f2ff70e63547b (diff) | |
bpf: Add x86-64 JIT support for bpf_addr_space_cast instruction.
LLVM generates bpf_addr_space_cast instruction while translating
pointers between native (zero) address space and
__attribute__((address_space(N))).
The addr_space=1 is reserved as bpf_arena address space.
rY = addr_space_cast(rX, 0, 1) is processed by the verifier and
converted to normal 32-bit move: wX = wY
rY = addr_space_cast(rX, 1, 0) has to be converted by JIT:
aux_reg = upper_32_bits of arena->user_vm_start
aux_reg <<= 32
wX = wY // clear upper 32 bits of dst register
if (wX) // if not zero add upper bits of user_vm_start
wX |= aux_reg
JIT can do it more efficiently:
mov dst_reg32, src_reg32 // 32-bit move
shl dst_reg, 32
or dst_reg, user_vm_start
rol dst_reg, 32
xor r11, r11
test dst_reg32, dst_reg32 // check if lower 32-bit are zero
cmove r11, dst_reg // if so, set dst_reg to zero
// Intel swapped src/dst register encoding in CMOVcc
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-5-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/core.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index a8ecf69c7754..bdbdc75cdcd5 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2932,6 +2932,11 @@ bool __weak bpf_jit_supports_far_kfunc_call(void) return false; } +bool __weak bpf_jit_supports_arena(void) +{ + return false; +} + /* Return TRUE if the JIT backend satisfies the following two conditions: * 1) JIT backend supports atomic_xchg() on pointer-sized words. * 2) Under the specific arch, the implementation of xchg() is the same |