On Mon, Feb 20, 2023 at 10:22 PM 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.
>
> Signed-off-by: Puranjay Mohan <puranjay12@xxxxxxxxx>
> ---
> tools/lib/bpf/usdt.c | 82 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 82 insertions(+)
>
> diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
> index 75b411fc2c77..ef097b882a4d 100644
> --- a/tools/lib/bpf/usdt.c
> +++ b/tools/lib/bpf/usdt.c
> @@ -1505,6 +1505,88 @@ 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)
> +{
> + int reg_num;
> +
> + if (sscanf(reg_name, "r%d", ®_num) == 1) {
> + if (reg_num >= 0 && reg_num <= 10)
> + return offsetof(struct pt_regs, uregs[reg_num]);
> + } else if (strcmp(reg_name, "fp") == 0) {
> + return offsetof(struct pt_regs, ARM_fp);
> + } else if (strcmp(reg_name, "ip") == 0) {
> + return offsetof(struct pt_regs, ARM_ip);
> + } else if (strcmp(reg_name, "sp") == 0) {
> + return offsetof(struct pt_regs, ARM_sp);
> + } else if (strcmp(reg_name, "lr") == 0) {
> + return offsetof(struct pt_regs, ARM_lr);
> + } else if (strcmp(reg_name, "pc") == 0) {
> + return offsetof(struct pt_regs, ARM_pc);
> + }
> + 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)
> +{
> + char reg_name[16];
> + int arg_sz, len, reg_off;
> + long off;
> +
> + if (sscanf(arg_str, " %d @ \[ %15[a-z0-9], #%ld ] %n", &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;
> + }
> +
> + arg->arg_signed = arg_sz < 0;
> + if (arg_sz < 0)
> + arg_sz = -arg_sz;
> +
> + switch (arg_sz) {
> + case 1: case 2: case 4: case 8:
> + arg->arg_bitshift = 64 - arg_sz * 8;
> + break;
> + default:
> + pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n",
> + arg_num, arg_str, arg_sz);
> + return -EINVAL;
> + }
> +
> + return len;
> +}
> +
> #else
>
> static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)
> --
> 2.39.1
>
Will send again with a fixed subject string.
--
Thanks and Regards
Yours Truly,
Puranjay Mohan
