On 09/12/2024 14:54, Simone Magnani wrote: > This patch introduces a new probe to check whether the kernel supports > instruction set extensions v4. The v4 extension comprises several new > instructions: BPF_{SDIV,SMOD} (signed div and mod), BPF_{LD,LDX,ST,STX,MOV} > (sign-extended load/store/move), 32-bit BPF_JA (unconditional jump), > target-independent BPF_ALU64 BSWAP (byte-swapping 16/32/64). These have > been introduced in the following commits respectively: > > * ec0e2da ("bpf: Support new signed div/mod instructions.") > * 1f9a1ea ("bpf: Support new sign-extension load insns") > * 8100928 ("bpf: Support new sign-extension mov insns") > * 4cd58e9 ("bpf: Support new 32bit offset jmp instruction") > * 0845c3d ("bpf: Support new unconditional bswap instruction") > > Support in bpftool for previous ISA extensions were added in commit > 0fd800b2 ("bpftool: Probe for instruction set extensions"). These probes > are useful for userspace BPF projects that want to use newer > instruction set extensions on newer kernels, to reduce the programs' > sizes or their complexity. LLVM provides the mcpu=v4 option since commit > "[BPF] support for BPF_ST instruction in codegen" > (https://github.com/llvm/llvm-project/commit/8f28e8069c4ba1110daee8bddc4d5049b6d4646e). > > Changelog: > > - v2: > - moved BPF_JMP32_A macro after BPF_JMP_A in filter.h for consistency > with include/linux/filter.h, noted by Quentin Monnet <qmo@xxxxxxxxxx> > > Signed-off-by: Simone Magnani <simone.magnani@xxxxxxxxxxxxx> > --- > tools/bpf/bpftool/feature.c | 23 +++++++++++++++++++++++ > tools/include/linux/filter.h | 10 ++++++++++ > 2 files changed, 33 insertions(+) > > diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c > index 4dbc4fcdf473..24fecdf8e430 100644 > --- a/tools/bpf/bpftool/feature.c > +++ b/tools/bpf/bpftool/feature.c > @@ -885,6 +885,28 @@ probe_v3_isa_extension(const char *define_prefix, __u32 ifindex) > "V3_ISA_EXTENSION"); > } > > +/* > + * Probe for the v4 instruction set extension introduced in commit 1f9a1ea821ff > + * ("bpf: Support new sign-extension load insns"). > + */ > +static void > +probe_v4_isa_extension(const char *define_prefix, __u32 ifindex) > +{ > + struct bpf_insn insns[5] = { > + BPF_MOV64_IMM(BPF_REG_0, 0), > + BPF_JMP32_IMM(BPF_JEQ, BPF_REG_0, 1, 1), Looking again at the probe itself, does the second instruction serve any practical purpose here? Don't you just need to test the BPF_JMP32_A? Looks good otherwise, thank you! Reviewed-by: Quentin Monnet <qmo@xxxxxxxxxx> > + BPF_JMP32_A(1), > + BPF_MOV64_IMM(BPF_REG_0, 1), > + BPF_EXIT_INSN() > + };