tools/testing/selftests/x86/single_step_syscall.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/x86/single_step_syscall.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/x86/single_step_syscall.c
Extension
.c
Size
5804 bytes
Lines
221
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: syscall or user/kernel boundary
Status
core implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * single_step_syscall.c - single-steps various x86 syscalls
 * Copyright (c) 2014-2015 Andrew Lutomirski
 *
 * This is a very simple series of tests that makes system calls with
 * the TF flag set.  This exercises some nasty kernel code in the
 * SYSENTER case: SYSENTER does not clear TF, so SYSENTER with TF set
 * immediately issues #DB from CPL 0.  This requires special handling in
 * the kernel.
 */

#define _GNU_SOURCE

#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <sys/signal.h>
#include <sys/ucontext.h>
#include <asm/ldt.h>
#include <err.h>
#include <setjmp.h>
#include <stddef.h>
#include <stdbool.h>
#include <sys/ptrace.h>
#include <sys/user.h>

#include "helpers.h"

static volatile sig_atomic_t sig_traps, sig_eflags;
sigjmp_buf jmpbuf;

#ifdef __x86_64__
# define REG_IP REG_RIP
# define WIDTH "q"
# define INT80_CLOBBERS "r8", "r9", "r10", "r11"
#else
# define REG_IP REG_EIP
# define WIDTH "l"
# define INT80_CLOBBERS
#endif

static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
	ucontext_t *ctx = (ucontext_t*)ctx_void;

	if (get_eflags() & X86_EFLAGS_TF) {
		set_eflags(get_eflags() & ~X86_EFLAGS_TF);
		printf("[WARN]\tSIGTRAP handler had TF set\n");
		_exit(1);
	}

	sig_traps++;

	if (sig_traps == 10000 || sig_traps == 10001) {
		printf("[WARN]\tHit %d SIGTRAPs with si_addr 0x%lx, ip 0x%lx\n",
		       (int)sig_traps,
		       (unsigned long)info->si_addr,
		       (unsigned long)ctx->uc_mcontext.gregs[REG_IP]);
	}
}

static char const * const signames[] = {
	[SIGSEGV] = "SIGSEGV",
	[SIGBUS] = "SIBGUS",
	[SIGTRAP] = "SIGTRAP",
	[SIGILL] = "SIGILL",
};

static void print_and_longjmp(int sig, siginfo_t *si, void *ctx_void)
{
	ucontext_t *ctx = ctx_void;

	printf("\tGot %s with RIP=%lx, TF=%ld\n", signames[sig],
	       (unsigned long)ctx->uc_mcontext.gregs[REG_IP],
	       (unsigned long)ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_TF);

	sig_eflags = (unsigned long)ctx->uc_mcontext.gregs[REG_EFL];
	siglongjmp(jmpbuf, 1);
}

static void check_result(void)
{
	unsigned long new_eflags = get_eflags();

Annotation

Implementation Notes