ptrace.c

/*
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Derived from "arch/m68k/kernel/ptrace.c"
 *  Copyright (C) 1994 by Hamish Macdonald
 *  Taken from linux/kernel/ptrace.c and modified for M680x0.
 *  linux/kernel/ptrace.c is by Ross Biro 1/23/92, edited by Linus Torvalds
 *
 * Modified by Cort Dougan (cort@hq.fsmlabs.com)
 * and Paul Mackerras (paulus@samba.org).
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file README.legal in the main directory of
 * this archive for more details.
 */

#include <linux/regset.h>
#include <linux/tracehook.h>
#include <linux/audit.h>
#include <linux/context_tracking.h>
#include <linux/syscalls.h>

#include <asm/switch_to.h>
#include <asm/asm-prototypes.h>
#include <asm/debug.h>

#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>

#include "ptrace-decl.h"

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure single step bits etc are not set.
 */
void ptrace_disable(struct task_struct *child)
{
	/* make sure the single step bit is not set. */
	user_disable_single_step(child);
}

long arch_ptrace(struct task_struct *child, long request,
		 unsigned long addr, unsigned long data)
{
	int ret = -EPERM;
	void __user *datavp = (void __user *) data;
	unsigned long __user *datalp = datavp;

	switch (request) {
	/* read the word at location addr in the USER area. */
	case PTRACE_PEEKUSR: {
		unsigned long index, tmp;

		ret = -EIO;
		/* convert to index and check */
		index = addr / sizeof(long);
		if ((addr & (sizeof(long) - 1)) || !child->thread.regs)
			break;

		if (index < PT_FPR0)
			ret = ptrace_get_reg(child, (int) index, &tmp);
		else
			ret = ptrace_get_fpr(child, index, &tmp);

		if (ret)
			break;
		ret = put_user(tmp, datalp);
		break;
	}

	/* write the word at location addr in the USER area */
	case PTRACE_POKEUSR: {
		unsigned long index;

		ret = -EIO;
		/* convert to index and check */
		index = addr / sizeof(long);
		if ((addr & (sizeof(long) - 1)) || !child->thread.regs)
			break;

		if (index < PT_FPR0)
			ret = ptrace_put_reg(child, index, data);
		else
			ret = ptrace_put_fpr(child, index, data);
		break;
	}

	case PPC_PTRACE_GETHWDBGINFO: {
		struct ppc_debug_info dbginfo;

		ppc_gethwdinfo(&dbginfo);

		if (copy_to_user(datavp, &dbginfo,
				 sizeof(struct ppc_debug_info)))
			return -EFAULT;
		return 0;
	}

	case PPC_PTRACE_SETHWDEBUG: {
		struct ppc_hw_breakpoint bp_info;

		if (copy_from_user(&bp_info, datavp,
				   sizeof(struct ppc_hw_breakpoint)))
			return -EFAULT;
		return ppc_set_hwdebug(child, &bp_info);
	}

	case PPC_PTRACE_DELHWDEBUG: {
		ret = ppc_del_hwdebug(child, data);
		break;
	}

	case PTRACE_GET_DEBUGREG:
		ret = ptrace_get_debugreg(child, addr, datalp);
		break;

	case PTRACE_SET_DEBUGREG:
		ret = ptrace_set_debugreg(child, addr, data);
		break;

#ifdef CONFIG_PPC64
	case PTRACE_GETREGS64:
#endif
	case PTRACE_GETREGS:	/* Get all pt_regs from the child. */
		return copy_regset_to_user(child, &user_ppc_native_view,
					   REGSET_GPR,
					   0, sizeof(struct user_pt_regs),
					   datavp);

#ifdef CONFIG_PPC64
	case PTRACE_SETREGS64:
#endif
	case PTRACE_SETREGS:	/* Set all gp regs in the child. */
		return copy_regset_from_user(child, &user_ppc_native_view,
					     REGSET_GPR,
					     0, sizeof(struct user_pt_regs),
					     datavp);

	case PTRACE_GETFPREGS: /* Get the child FPU state (FPR0...31 + FPSCR) */
		return copy_regset_to_user(child, &user_ppc_native_view,
					   REGSET_FPR,
					   0, sizeof(elf_fpregset_t),
					   datavp);

	case PTRACE_SETFPREGS: /* Set the child FPU state (FPR0...31 + FPSCR) */
		return copy_regset_from_user(child, &user_ppc_native_view,
					     REGSET_FPR,
					     0, sizeof(elf_fpregset_t),
					     datavp);

#ifdef CONFIG_ALTIVEC
	case PTRACE_GETVRREGS:
		return copy_regset_to_user(child, &user_ppc_native_view,
					   REGSET_VMX,
					   0, (33 * sizeof(vector128) +
					       sizeof(u32)),
					   datavp);

	case PTRACE_SETVRREGS:
		return copy_regset_from_user(child, &user_ppc_native_view,
					     REGSET_VMX,
					     0, (33 * sizeof(vector128) +
						 sizeof(u32)),
					     datavp);
#endif
#ifdef CONFIG_VSX
	case PTRACE_GETVSRREGS:
		return copy_regset_to_user(child, &user_ppc_native_view,
					   REGSET_VSX,
					   0, 32 * sizeof(double),
					   datavp);

	case PTRACE_SETVSRREGS:
		return copy_regset_from_user(child, &user_ppc_native_view,
					     REGSET_VSX,
					     0, 32 * sizeof(double),
					     datavp);
#endif
#ifdef CONFIG_SPE
	case PTRACE_GETEVRREGS:
		/* Get the child spe register state. */
		return copy_regset_to_user(child, &user_ppc_native_view,
					   REGSET_SPE, 0, 35 * sizeof(u32),
					   datavp);

	case PTRACE_SETEVRREGS:
		/* Set the child spe register state. */
		return copy_regset_from_user(child, &user_ppc_native_view,
					     REGSET_SPE, 0, 35 * sizeof(u32),
					     datavp);
#endif

	default:
		ret = ptrace_request(child, request, addr, data);
		break;
	}
	return ret;
}

#ifdef CONFIG_SECCOMP
static int do_seccomp(struct pt_regs *regs)
{
	if (!test_thread_flag(TIF_SECCOMP))
		return 0;

	/*
	 * The ABI we present to seccomp tracers is that r3 contains
	 * the syscall return value and orig_gpr3 contains the first
	 * syscall parameter. This is different to the ptrace ABI where
	 * both r3 and orig_gpr3 contain the first syscall parameter.
	 */
	regs->gpr[3] = -ENOSYS;

	/*
	 * We use the __ version here because we have already checked
	 * TIF_SECCOMP. If this fails, there is nothing left to do, we
	 * have already loaded -ENOSYS into r3, or seccomp has put
	 * something else in r3 (via SECCOMP_RET_ERRNO/TRACE).
	 */
	if (__secure_computing(NULL))
		return -1;

	/*
	 * The syscall was allowed by seccomp, restore the register
	 * state to what audit expects.
	 * Note that we use orig_gpr3, which means a seccomp tracer can
	 * modify the first syscall parameter (in orig_gpr3) and also
	 * allow the syscall to proceed.
	 */
	regs->gpr[3] = regs->orig_gpr3;

	return 0;
}
#else
static inline int do_seccomp(struct pt_regs *regs) { return 0; }
#endif /* CONFIG_SECCOMP */

/**
 * do_syscall_trace_enter() - Do syscall tracing on kernel entry.
 * @regs: the pt_regs of the task to trace (current)
 *
 * Performs various types of tracing on syscall entry. This includes seccomp,
 * ptrace, syscall tracepoints and audit.
 *
 * The pt_regs are potentially visible to userspace via ptrace, so their
 * contents is ABI.
 *
 * One or more of the tracers may modify the contents of pt_regs, in particular
 * to modify arguments or even the syscall number itself.
 *
 * It's also possible that a tracer can choose to reject the system call. In
 * that case this function will return an illegal syscall number, and will put
 * an appropriate return value in regs->r3.
 *
 * Return: the (possibly changed) syscall number.
 */
long do_syscall_trace_enter(struct pt_regs *regs)
{
	u32 flags;

	flags = READ_ONCE(current_thread_info()->flags) &
		(_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE);

	if (flags) {
		int rc = tracehook_report_syscall_entry(regs);

		if (unlikely(flags & _TIF_SYSCALL_EMU)) {
			/*
			 * A nonzero return code from
			 * tracehook_report_syscall_entry() tells us to prevent
			 * the syscall execution, but we are not going to
			 * execute it anyway.
			 *
			 * Returning -1 will skip the syscall execution. We want
			 * to avoid clobbering any registers, so we don't goto
			 * the skip label below.
			 */
			return -1;
		}

		if (rc) {
			/*
			 * The tracer decided to abort the syscall. Note that
			 * the tracer may also just change regs->gpr[0] to an
			 * invalid syscall number, that is handled below on the
			 * exit path.
			 */
			goto skip;
		}
	}

	/* Run seccomp after ptrace; allow it to set gpr[3]. */
	if (do_seccomp(regs))
		return -1;

	/* Avoid trace and audit when syscall is invalid. */
	if (regs->gpr[0] >= NR_syscalls)
		goto skip;

	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
		trace_sys_enter(regs, regs->gpr[0]);

	if (!is_32bit_task())
		audit_syscall_entry(regs->gpr[0], regs->gpr[3], regs->gpr[4],
				    regs->gpr[5], regs->gpr[6]);
	else
		audit_syscall_entry(regs->gpr[0],
				    regs->gpr[3] & 0xffffffff,
				    regs->gpr[4] & 0xffffffff,
				    regs->gpr[5] & 0xffffffff,
				    regs->gpr[6] & 0xffffffff);

	/* Return the possibly modified but valid syscall number */
	return regs->gpr[0];

skip:
	/*
	 * If we are aborting explicitly, or if the syscall number is
	 * now invalid, set the return value to -ENOSYS.
	 */
	regs->gpr[3] = -ENOSYS;
	return -1;
}

void do_syscall_trace_leave(struct pt_regs *regs)
{
	int step;

	audit_syscall_exit(regs);

	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
		trace_sys_exit(regs, regs->result);

	step = test_thread_flag(TIF_SINGLESTEP);
	if (step || test_thread_flag(TIF_SYSCALL_TRACE))
		tracehook_report_syscall_exit(regs, step);
}

void __init pt_regs_check(void);

/*
 * Dummy function, its purpose is to break the build if struct pt_regs and
 * struct user_pt_regs don't match.
 */
void __init pt_regs_check(void)
{
	BUILD_BUG_ON(offsetof(struct pt_regs, gpr) !=
		     offsetof(struct user_pt_regs, gpr));
	BUILD_BUG_ON(offsetof(struct pt_regs, nip) !=
		     offsetof(struct user_pt_regs, nip));
	BUILD_BUG_ON(offsetof(struct pt_regs, msr) !=
		     offsetof(struct user_pt_regs, msr));
	BUILD_BUG_ON(offsetof(struct pt_regs, orig_gpr3) !=
		     offsetof(struct user_pt_regs, orig_gpr3));
	BUILD_BUG_ON(offsetof(struct pt_regs, ctr) !=
		     offsetof(struct user_pt_regs, ctr));
	BUILD_BUG_ON(offsetof(struct pt_regs, link) !=
		     offsetof(struct user_pt_regs, link));
	BUILD_BUG_ON(offsetof(struct pt_regs, xer) !=
		     offsetof(struct user_pt_regs, xer));
	BUILD_BUG_ON(offsetof(struct pt_regs, ccr) !=
		     offsetof(struct user_pt_regs, ccr));
#ifdef __powerpc64__
	BUILD_BUG_ON(offsetof(struct pt_regs, softe) !=
		     offsetof(struct user_pt_regs, softe));
#else
	BUILD_BUG_ON(offsetof(struct pt_regs, mq) !=
		     offsetof(struct user_pt_regs, mq));
#endif
	BUILD_BUG_ON(offsetof(struct pt_regs, trap) !=
		     offsetof(struct user_pt_regs, trap));
	BUILD_BUG_ON(offsetof(struct pt_regs, dar) !=
		     offsetof(struct user_pt_regs, dar));
	BUILD_BUG_ON(offsetof(struct pt_regs, dear) !=
		     offsetof(struct user_pt_regs, dar));
	BUILD_BUG_ON(offsetof(struct pt_regs, dsisr) !=
		     offsetof(struct user_pt_regs, dsisr));
	BUILD_BUG_ON(offsetof(struct pt_regs, esr) !=
		     offsetof(struct user_pt_regs, dsisr));
	BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
		     offsetof(struct user_pt_regs, result));

	BUILD_BUG_ON(sizeof(struct user_pt_regs) > sizeof(struct pt_regs));

	// Now check that the pt_regs offsets match the uapi #defines
	#define CHECK_REG(_pt, _reg) \
		BUILD_BUG_ON(_pt != (offsetof(struct user_pt_regs, _reg) / \
				     sizeof(unsigned long)));

	CHECK_REG(PT_R0,  gpr[0]);
	CHECK_REG(PT_R1,  gpr[1]);
	CHECK_REG(PT_R2,  gpr[2]);
	CHECK_REG(PT_R3,  gpr[3]);
	CHECK_REG(PT_R4,  gpr[4]);
	CHECK_REG(PT_R5,  gpr[5]);
	CHECK_REG(PT_R6,  gpr[6]);
	CHECK_REG(PT_R7,  gpr[7]);
	CHECK_REG(PT_R8,  gpr[8]);
	CHECK_REG(PT_R9,  gpr[9]);
	CHECK_REG(PT_R10, gpr[10]);
	CHECK_REG(PT_R11, gpr[11]);
	CHECK_REG(PT_R12, gpr[12]);
	CHECK_REG(PT_R13, gpr[13]);
	CHECK_REG(PT_R14, gpr[14]);
	CHECK_REG(PT_R15, gpr[15]);
	CHECK_REG(PT_R16, gpr[16]);
	CHECK_REG(PT_R17, gpr[17]);
	CHECK_REG(PT_R18, gpr[18]);
	CHECK_REG(PT_R19, gpr[19]);
	CHECK_REG(PT_R20, gpr[20]);
	CHECK_REG(PT_R21, gpr[21]);
	CHECK_REG(PT_R22, gpr[22]);
	CHECK_REG(PT_R23, gpr[23]);
	CHECK_REG(PT_R24, gpr[24]);
	CHECK_REG(PT_R25, gpr[25]);
	CHECK_REG(PT_R26, gpr[26]);
	CHECK_REG(PT_R27, gpr[27]);
	CHECK_REG(PT_R28, gpr[28]);
	CHECK_REG(PT_R29, gpr[29]);
	CHECK_REG(PT_R30, gpr[30]);
	CHECK_REG(PT_R31, gpr[31]);
	CHECK_REG(PT_NIP, nip);
	CHECK_REG(PT_MSR, msr);
	CHECK_REG(PT_ORIG_R3, orig_gpr3);
	CHECK_REG(PT_CTR, ctr);
	CHECK_REG(PT_LNK, link);
	CHECK_REG(PT_XER, xer);
	CHECK_REG(PT_CCR, ccr);
#ifdef CONFIG_PPC64
	CHECK_REG(PT_SOFTE, softe);
#else
	CHECK_REG(PT_MQ, mq);
#endif
	CHECK_REG(PT_TRAP, trap);
	CHECK_REG(PT_DAR, dar);
	CHECK_REG(PT_DSISR, dsisr);
	CHECK_REG(PT_RESULT, result);
	#undef CHECK_REG

	BUILD_BUG_ON(PT_REGS_COUNT != sizeof(struct user_pt_regs) / sizeof(unsigned long));

	/*
	 * PT_DSCR isn't a real reg, but it's important that it doesn't overlap the
	 * real registers.
	 */
	BUILD_BUG_ON(PT_DSCR < sizeof(struct user_pt_regs) / sizeof(unsigned long));

	// ptrace_get/put_fpr() rely on PPC32 and VSX being incompatible
	BUILD_BUG_ON(IS_ENABLED(CONFIG_PPC32) && IS_ENABLED(CONFIG_VSX));
}