Naveen N Rao d243b62b7b powerpc64/bpf: Add support for bpf trampolines ... Add support for bpf_arch_text_poke() and arch_prepare_bpf_trampoline() for 64-bit powerpc. While the code is generic, BPF trampolines are only enabled on 64-bit powerpc. 32-bit powerpc will need testing and some updates. BPF Trampolines adhere to the existing ftrace ABI utilizing a two-instruction profiling sequence, as well as the newer ABI utilizing a three-instruction profiling sequence enabling return with a 'blr'. The trampoline code itself closely follows x86 implementation. BPF prog JIT is extended to mimic 64-bit powerpc approach for ftrace having a single nop at function entry, followed by the function profiling sequence out-of-line and a separate long branch stub for calls to trampolines that are out of range. A dummy_tramp is provided to simplify synchronization similar to arm64. When attaching a bpf trampoline to a bpf prog, we can patch up to three things: - the nop at bpf prog entry to go to the out-of-line stub - the instruction in the out-of-line stub to either call the bpf trampoline directly, or to branch to the long_branch stub. - the trampoline address before the long_branch stub. We do not need any synchronization here since we always have a valid branch target regardless of the order in which the above stores are seen. dummy_tramp ensures that the long_branch stub goes to a valid destination on other cpus, even when the branch to the long_branch stub is seen before the updated trampoline address. However, when detaching a bpf trampoline from a bpf prog, or if changing the bpf trampoline address, we need synchronization to ensure that other cpus can no longer branch into the older trampoline so that it can be safely freed. bpf_tramp_image_put() uses rcu_tasks to ensure all cpus make forward progress, but we still need to ensure that other cpus execute isync (or some CSI) so that they don't go back into the trampoline again. While here, update the stale comment that describes the redzone usage in ppc64 BPF JIT. Signed-off-by: Naveen N Rao <naveen@kernel.org> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://patch.msgid.link/20241030070850.1361304-18-hbathini@linux.ibm.com		2024-10-31 11:00:55 +11:00
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bpf_jit_comp32.c	powerpc64/bpf: Add support for bpf trampolines	2024-10-31 11:00:55 +11:00
bpf_jit_comp64.c	powerpc64/bpf: Add support for bpf trampolines	2024-10-31 11:00:55 +11:00
bpf_jit_comp.c	powerpc64/bpf: Add support for bpf trampolines	2024-10-31 11:00:55 +11:00
bpf_jit.h	powerpc64/bpf: Add support for bpf trampolines	2024-10-31 11:00:55 +11:00
Makefile	powerpc/bpf: Implement extended BPF on PPC32	2021-04-03 21:22:21 +11:00