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libbpf: Support riscv USDT argument parsing logic

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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
This commit is contained in:
Pu Lehui 2022-04-19 22:52:38 +08:00 committed by Andrii Nakryiko
parent 5af25a410a
commit 58ca8b0572
1 changed files with 107 additions and 0 deletions
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107
tools/lib/bpf/usdt.c
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@ -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)