libbpf: Support riscv USDT argument parsing logic

Add riscv-specific USDT argument specification parsing logic.
riscv USDT argument format is shown below:
- Memory dereference case:
  "size@off(reg)", e.g. "-8@-88(s0)"
- Constant value case:
  "size@val", e.g. "4@5"
- Register read case:
  "size@reg", e.g. "-8@a1"

s8 will be marked as poison while it's a reg of riscv, we need
to alias it in advance. Both RV32 and RV64 have been tested.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220419145238.482134-3-pulehui@huawei.com

diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index 8e77a72..f1c9339 100644 (file)
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -10,6 +10,11 @@
 #include <linux/ptrace.h>
 #include <linux/kernel.h>
 
+/* s8 will be marked as poison while it's a reg of riscv */
+#if defined(__riscv)
+#define rv_s8 s8
+#endif
+
 #include "bpf.h"
 #include "libbpf.h"
 #include "libbpf_common.h"
@@ -1400,6 +1405,108 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
        return len;
 }
 
+#elif defined(__riscv)
+
+static int calc_pt_regs_off(const char *reg_name)
+{
+       static struct {
+               const char *name;
+               size_t pt_regs_off;
+       } reg_map[] = {
+               { "ra", offsetof(struct user_regs_struct, ra) },
+               { "sp", offsetof(struct user_regs_struct, sp) },
+               { "gp", offsetof(struct user_regs_struct, gp) },
+               { "tp", offsetof(struct user_regs_struct, tp) },
+               { "a0", offsetof(struct user_regs_struct, a0) },
+               { "a1", offsetof(struct user_regs_struct, a1) },
+               { "a2", offsetof(struct user_regs_struct, a2) },
+               { "a3", offsetof(struct user_regs_struct, a3) },
+               { "a4", offsetof(struct user_regs_struct, a4) },
+               { "a5", offsetof(struct user_regs_struct, a5) },
+               { "a6", offsetof(struct user_regs_struct, a6) },
+               { "a7", offsetof(struct user_regs_struct, a7) },
+               { "s0", offsetof(struct user_regs_struct, s0) },
+               { "s1", offsetof(struct user_regs_struct, s1) },
+               { "s2", offsetof(struct user_regs_struct, s2) },
+               { "s3", offsetof(struct user_regs_struct, s3) },
+               { "s4", offsetof(struct user_regs_struct, s4) },
+               { "s5", offsetof(struct user_regs_struct, s5) },
+               { "s6", offsetof(struct user_regs_struct, s6) },
+               { "s7", offsetof(struct user_regs_struct, s7) },
+               { "s8", offsetof(struct user_regs_struct, rv_s8) },
+               { "s9", offsetof(struct user_regs_struct, s9) },
+               { "s10", offsetof(struct user_regs_struct, s10) },
+               { "s11", offsetof(struct user_regs_struct, s11) },
+               { "t0", offsetof(struct user_regs_struct, t0) },
+               { "t1", offsetof(struct user_regs_struct, t1) },
+               { "t2", offsetof(struct user_regs_struct, t2) },
+               { "t3", offsetof(struct user_regs_struct, t3) },
+               { "t4", offsetof(struct user_regs_struct, t4) },
+               { "t5", offsetof(struct user_regs_struct, t5) },
+               { "t6", offsetof(struct user_regs_struct, t6) },
+       };
+       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)
+{
+       char *reg_name = NULL;
+       int arg_sz, len, reg_off;
+       long off;
+
+       if (sscanf(arg_str, " %d @ %ld ( %m[a-z0-9] ) %n", &arg_sz, &off, &reg_name, &len) == 3) {
+               /* Memory dereference case, e.g., -8@-88(s0) */
+               arg->arg_type = USDT_ARG_REG_DEREF;
+               arg->val_off = off;
+               reg_off = calc_pt_regs_off(reg_name);
+               free(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 @ %m[a-z0-9] %n", &arg_sz, &reg_name, &len) == 2) {
+               /* Register read case, e.g., -8@a1 */
+               arg->arg_type = USDT_ARG_REG;
+               arg->val_off = 0;
+               reg_off = calc_pt_regs_off(reg_name);
+               free(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)