Commit 58ca8b05 authored by Pu Lehui's avatar Pu Lehui Committed by Andrii Nakryiko
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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: default avatarPu Lehui <pulehui@huawei.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220419145238.482134-3-pulehui@huawei.com
parent 5af25a41

tools/lib/bpf/usdt.c

+107 −0
Original line number Diff line number Diff line
@@ -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)