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Parsing of USDT arguments is architecture-specific; on arm it is relatively easy since registers used are r[0-10], fp, ip, sp, lr, pc. Format is slightly different compared to aarch64; forms are - "size @ [ reg, #offset ]" for dereferences, for example "-8 @ [ sp, #76 ]" ; " -4 @ [ sp ]" - "size @ reg" for register values; for example "-4@r0" - "size @ #value" for raw values; for example "-8@#1" Add support for parsing USDT arguments for ARM architecture. To test the above changes QEMU's virt[1] board with cortex-a15 CPU was used. libbpf-bootstrap's usdt example[2] was modified to attach to a test program with DTRACE_PROBE1/2/3/4... probes to test different combinations. [1] https://www.qemu.org/docs/master/system/arm/virt.html [2] https://github.com/libbpf/libbpf-bootstrap/blob/master/examples/c/usdt.bpf.c Signed-off-by: Puranjay Mohan <puranjay12@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20230307120440.25941-3-puranjay12@gmail.com