From b9fee10a52c0999f6f1c7e1c0ea83869f3cd10ae Mon Sep 17 00:00:00 2001 From: Simone Magnani Date: Mon, 9 Dec 2024 15:54:39 +0100 Subject: [PATCH] bpftool: Probe for ISA v4 instruction set extension 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: * ec0e2da95f72 ("bpf: Support new signed div/mod instructions.") * 1f9a1ea821ff ("bpf: Support new sign-extension load insns") * 8100928c8814 ("bpf: Support new sign-extension mov insns") * 4cd58e9af8b9 ("bpf: Support new 32bit offset jmp instruction") * 0845c3db7bf5 ("bpf: Support new unconditional bswap instruction") Support in bpftool for previous ISA extensions was added in commit 0fd800b2456c ("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 LLVM commit 8f28e8069c4b ("[BPF] support for BPF_ST instruction in codegen") [0]. Signed-off-by: Simone Magnani Signed-off-by: Daniel Borkmann Reviewed-by: Quentin Monnet Link: https://github.com/llvm/llvm-project/commit/8f28e8069c4ba1110daee8bddc4d5049b6d4646e [0] Link: https://lore.kernel.org/bpf/20241209145439.336362-1-simone.magnani@isovalent.com --- 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), + BPF_JMP32_A(1), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN() + }; + + probe_misc_feature(insns, ARRAY_SIZE(insns), + define_prefix, ifindex, + "have_v4_isa_extension", + "ISA extension v4", + "V4_ISA_EXTENSION"); +} + static void section_system_config(enum probe_component target, const char *define_prefix) { @@ -1029,6 +1051,7 @@ static void section_misc(const char *define_prefix, __u32 ifindex) probe_bounded_loops(define_prefix, ifindex); probe_v2_isa_extension(define_prefix, ifindex); probe_v3_isa_extension(define_prefix, ifindex); + probe_v4_isa_extension(define_prefix, ifindex); print_end_section(); } diff --git a/tools/include/linux/filter.h b/tools/include/linux/filter.h index 65aa8ce142e5..bcc6df79301a 100644 --- a/tools/include/linux/filter.h +++ b/tools/include/linux/filter.h @@ -273,6 +273,16 @@ .off = OFF, \ .imm = 0 }) +/* Unconditional jumps, gotol pc + imm32 */ + +#define BPF_JMP32_A(IMM) \ + ((struct bpf_insn) { \ + .code = BPF_JMP32 | BPF_JA, \ + .dst_reg = 0, \ + .src_reg = 0, \ + .off = 0, \ + .imm = IMM }) + /* Function call */ #define BPF_EMIT_CALL(FUNC) \ -- 2.25.1