On Tue, Mar 7, 2023 at 4:04 AM Puranjay Mohan <puranjay12@xxxxxxxxx> wrote: > > 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@xxxxxxxxx> > --- > tools/lib/bpf/usdt.c | 80 ++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 80 insertions(+) > > diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c > index 293b7a37f8a1..27a4589eda1c 100644 > --- a/tools/lib/bpf/usdt.c > +++ b/tools/lib/bpf/usdt.c > @@ -1466,6 +1466,86 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec > return len; > } > > +#elif defined(__arm__) > + > +static int calc_pt_regs_off(const char *reg_name) > +{ > + static struct { > + const char *name; > + size_t pt_regs_off; > + } reg_map[] = { > + { "r0", offsetof(struct pt_regs, uregs[0]) }, > + { "r1", offsetof(struct pt_regs, uregs[1]) }, > + { "r2", offsetof(struct pt_regs, uregs[2]) }, > + { "r3", offsetof(struct pt_regs, uregs[3]) }, > + { "r4", offsetof(struct pt_regs, uregs[4]) }, > + { "r5", offsetof(struct pt_regs, uregs[5]) }, > + { "r6", offsetof(struct pt_regs, uregs[6]) }, > + { "r7", offsetof(struct pt_regs, uregs[7]) }, > + { "r8", offsetof(struct pt_regs, uregs[8]) }, > + { "r9", offsetof(struct pt_regs, uregs[9]) }, > + { "r10", offsetof(struct pt_regs, uregs[10]) }, > + { "fp", offsetof(struct pt_regs, uregs[11]) }, > + { "ip", offsetof(struct pt_regs, uregs[12]) }, > + { "sp", offsetof(struct pt_regs, uregs[13]) }, > + { "lr", offsetof(struct pt_regs, uregs[14]) }, > + { "pc", offsetof(struct pt_regs, uregs[15]) }, > + }; > + int i; > + > + for (i = 0; i < ARRAY_SIZE(reg_map); i++) { > + if (strcmp(reg_name, reg_map[i].name) == 0) > + return reg_map[i].pt_regs_off; > + } > + > + pr_warn("usdt: unrecognized register '%s'\n", reg_name); > + return -ENOENT; > +} > + > +static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz) > +{ > + char reg_name[16]; > + int len, reg_off; > + long off; > + > + if (sscanf(arg_str, " %d @ \[ %15[a-z0-9], #%ld ] %n", I've added space before , and applied to bpf-next. Thanks, it's a nice clean up and wider architecture support! BTW, I noticed that we don't support fp, ip, lr, and pc (only sp) for __aarch64__, why such a difference between 32-bit and 64-bit arms? > + arg_sz, reg_name, &off, &len) == 3) { > + /* Memory dereference case, e.g., -4@[fp, #96] */ > + arg->arg_type = USDT_ARG_REG_DEREF; > + arg->val_off = off; > + reg_off = calc_pt_regs_off(reg_name); > + if (reg_off < 0) > + return reg_off; > + arg->reg_off = reg_off; > + } else if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] ] %n", arg_sz, reg_name, &len) == 2) { > + /* Memory dereference case, e.g., -4@[sp] */ > + arg->arg_type = USDT_ARG_REG_DEREF; > + arg->val_off = 0; > + reg_off = calc_pt_regs_off(reg_name); > + if (reg_off < 0) > + return reg_off; > + arg->reg_off = reg_off; > + } else if (sscanf(arg_str, " %d @ #%ld %n", arg_sz, &off, &len) == 2) { > + /* Constant value case, e.g., 4@#5 */ > + arg->arg_type = USDT_ARG_CONST; > + arg->val_off = off; > + arg->reg_off = 0; > + } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) { > + /* Register read case, e.g., -8@r4 */ > + arg->arg_type = USDT_ARG_REG; > + arg->val_off = 0; > + reg_off = calc_pt_regs_off(reg_name); > + if (reg_off < 0) > + return reg_off; > + arg->reg_off = reg_off; > + } else { > + pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str); > + return -EINVAL; > + } > + > + return len; > +} > + > #else > > static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz) > -- > 2.39.1 >
