bpf, riscv: inline bpf_get_current_task() and bpf_get_current_task_btf()

On RISC-V, the current task pointer is stored in the thread pointer
register (tp). Emit a single `mv a5, tp` instead of a full helper
call for BPF_FUNC_get_current_task and BPF_FUNC_get_current_task_btf.

Register bpf_jit_inlines_helper_call() entries for both helpers so the
verifier treats them as inlined, and add the expected `mv a5, tp`
annotation to the riscv64 selftests.

The following show changes before and after this patch.

Before patch:

      auipc  t1,0x817a    # load upper PC-relative address
      jalr   -2004(t1)    # call bpf_get_current_task helper
      mv     a5,a0        # move return value to BPF_REG_0

After patch:

      mv     a5,tp        # directly: a5 = current (tp = thread pointer)

Benchmark (bpf_prog_test_run wrapping bpf_get_current_task in loop,
batch=100, 10s, QEMU RISC-V):

              | runs/sec  | helper-calls/sec | ns/call
 -------------+-----------+------------------+---------
 Before patch |   173,490 |       17,349,090 |      57
 After patch  |   320,497 |       32,049,780 |      31
 -------------+-----------+------------------+---------
 Improvement  |   +84.7%  |          +84.7%  |  -45.6%

Signed-off-by: Varun R Mallya <varunrmallya@gmail.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20260602205847.102825-3-varunrmallya@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

0 files changed, 0 insertions, 0 deletions