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Add ptrace op PT_GET_SC_RET.

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This ptrace operation returns a structure containing the error and
return values from the current system call.  It is only valid when a
thread is stopped during a system call exit (PL_FLAG_SCX is set).

The sr_error member holds the error value from the system call.  Note
that this error value is the native FreeBSD error value that has _not_
been translated to an ABI-specific error value similar to the values
logged to ktrace.

If sr_error is zero, then the return values of the system call will be
set in sr_retval[0] and sr_retval[1].

Reviewed by:	kib
MFC after:	1 month
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D20901
This commit is contained in:
John Baldwin 2019-07-15 21:48:02 +00:00
parent 0cc1098a1a
commit 32451fb9fc
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=350017
4 changed files with 194 additions and 6 deletions
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48
lib/libc/sys/ptrace.2
View File

@ -2,7 +2,7 @@
.\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $
.\"
.\" This file is in the public domain.
.Dd June 2, 2018
.Dd July 15, 2019
.Dt PTRACE 2
.Os
.Sh NAME
@ -664,6 +664,52 @@ member of the
but not more than the
.Fa data
bytes in total are copied.
.It Dv PT_GET_SC_RET
Fetch the system call return values on exit from a syscall.
This request is only valid for threads stopped in a syscall
exit (the
.Dv PL_FLAG_SCX
state).
The
.Fa addr
argument specifies a pointer to a
.Vt "struct ptrace_sc_ret" ,
which is defined as follows:
.Bd -literal
struct ptrace_sc_ret {
register_t sr_retval[2];
int sr_error;
};
.Ed
.Pp
The
.Fa data
argument is set to the size of the structure.
.Pp
If the system call completed successfully,
.Va sr_error
is set to zero and the return values of the system call are saved in
.Va sr_retval .
If the system call failed to execute,
.Va sr_error
field is set to a positive
.Xr errno 2
value.
If the system call completed in an unusual fashion,
.Va sr_error
is set to a negative value:
.Pp
.Bl -tag -width Dv EJUSTRETURN -compact
.It Dv ERESTART
System call will be restarted.
.It Dv EJUSTRETURN
System call completed sucessfully but did not set a return value
.Po for example,
.Xr setcontext 2
and
.Xr sigreturn 2
.Pc .
.El
.It Dv PT_FOLLOW_FORK
This request controls tracing for new child processes of a traced process.
If

63
sys/kern/sys_process.c
View File

@ -76,6 +76,11 @@ struct ptrace_io_desc32 {
uint32_t piod_len;
};
struct ptrace_sc_ret32 {
uint32_t sr_retval[2];
int sr_error;
};
struct ptrace_vm_entry32 {
int pve_entry;
int pve_timestamp;
@ -518,6 +523,17 @@ ptrace_lwpinfo_to32(const struct ptrace_lwpinfo *pl,
pl32->pl_syscall_code = pl->pl_syscall_code;
pl32->pl_syscall_narg = pl->pl_syscall_narg;
}
static void
ptrace_sc_ret_to32(const struct ptrace_sc_ret *psr,
struct ptrace_sc_ret32 *psr32)
{
bzero(psr32, sizeof(*psr32));
psr32->sr_retval[0] = psr->sr_retval[0];
psr32->sr_retval[1] = psr->sr_retval[1];
psr32->sr_error = psr->sr_error;
}
#endif /* COMPAT_FREEBSD32 */
/*
@ -580,6 +596,7 @@ sys_ptrace(struct thread *td, struct ptrace_args *uap)
struct ptrace_vm_entry32 pve32;
#endif
char args[sizeof(td->td_sa.args)];
struct ptrace_sc_ret psr;
int ptevents;
} r;
void *addr;
@ -598,6 +615,7 @@ sys_ptrace(struct thread *td, struct ptrace_args *uap)
case PT_GET_EVENT_MASK:
case PT_LWPINFO:
case PT_GET_SC_ARGS:
case PT_GET_SC_RET:
break;
case PT_GETREGS:
BZERO(&r.reg, sizeof r.reg);
@ -668,6 +686,10 @@ sys_ptrace(struct thread *td, struct ptrace_args *uap)
error = copyout(r.args, uap->addr, MIN(uap->data,
sizeof(r.args)));
break;
case PT_GET_SC_RET:
error = copyout(&r.psr, uap->addr, MIN(uap->data,
sizeof(r.psr)));
break;
}
return (error);
@ -719,6 +741,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
struct thread *td2 = NULL, *td3;
struct ptrace_io_desc *piod = NULL;
struct ptrace_lwpinfo *pl;
struct ptrace_sc_ret *psr;
int error, num, tmp;
int proctree_locked = 0;
lwpid_t tid = 0, *buf;
@ -726,7 +749,11 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
int wrap32 = 0, safe = 0;
struct ptrace_io_desc32 *piod32 = NULL;
struct ptrace_lwpinfo32 *pl32 = NULL;
struct ptrace_lwpinfo plr;
struct ptrace_sc_ret32 *psr32 = NULL;
union {
struct ptrace_lwpinfo pl;
struct ptrace_sc_ret psr;
} r;
#endif
curp = td->td_proc;
@ -1049,6 +1076,38 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
bcopy(td2->td_sa.args, addr, td2->td_sa.narg *
sizeof(register_t));
break;
case PT_GET_SC_RET:
if ((td2->td_dbgflags & (TDB_SCX)) == 0
#ifdef COMPAT_FREEBSD32
|| (wrap32 && !safe)
#endif
) {
error = EINVAL;
break;
}
#ifdef COMPAT_FREEBSD32
if (wrap32) {
psr = &r.psr;
psr32 = addr;
} else
#endif
psr = addr;
bzero(psr, sizeof(*psr));
psr->sr_error = td2->td_errno;
if (psr->sr_error == 0) {
psr->sr_retval[0] = td2->td_retval[0];
psr->sr_retval[1] = td2->td_retval[1];
}
#ifdef COMPAT_FREEBSD32
if (wrap32)
ptrace_sc_ret_to32(psr, psr32);
#endif
CTR4(KTR_PTRACE,
"PT_GET_SC_RET: pid %d error %d retval %#lx,%#lx",
p->p_pid, psr->sr_error, psr->sr_retval[0],
psr->sr_retval[1]);
break;
case PT_STEP:
case PT_CONTINUE:
@ -1335,7 +1394,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
}
#ifdef COMPAT_FREEBSD32
if (wrap32) {
pl = &plr;
pl = &r.pl;
pl32 = addr;
} else
#endif

7
sys/sys/ptrace.h
View File

@ -72,6 +72,7 @@
#define PT_SET_EVENT_MASK 26 /* set mask of optional events */
#define PT_GET_SC_ARGS 27 /* fetch syscall args */
#define PT_GET_SC_RET 28 /* fetch syscall results */
#define PT_GETREGS 33 /* get general-purpose registers */
#define PT_SETREGS 34 /* set general-purpose registers */
@ -155,6 +156,12 @@ struct ptrace_lwpinfo32 {
};
#endif
/* Argument structure for PT_GET_SC_RET. */
struct ptrace_sc_ret {
register_t sr_retval[2]; /* Only valid if sr_error == 0. */
int sr_error;
};
/* Argument structure for PT_VM_ENTRY. */
struct ptrace_vm_entry {
int pve_entry; /* Entry number used for iteration. */

82
tests/sys/kern/ptrace_test.c
View File

@ -3905,12 +3905,13 @@ ATF_TC_BODY(ptrace__PT_LWPINFO_stale_siginfo, tc)
}
/*
* A simple test of PT_GET_SC_ARGS.
* A simple test of PT_GET_SC_ARGS and PT_GET_SC_RET.
*/
ATF_TC_WITHOUT_HEAD(ptrace__syscall_args);
ATF_TC_BODY(ptrace__syscall_args, tc)
{
struct ptrace_lwpinfo pl;
struct ptrace_sc_ret psr;
pid_t fpid, wpid;
register_t args[2];
int events, status;
@ -3919,6 +3920,7 @@ ATF_TC_BODY(ptrace__syscall_args, tc)
if (fpid == 0) {
trace_me();
kill(getpid(), 0);
close(3);
exit(1);
}
@ -3930,9 +3932,9 @@ ATF_TC_BODY(ptrace__syscall_args, tc)
/*
* Continue the process ignoring the signal, but enabling
* syscall entry traps.
* syscall traps.
*/
ATF_REQUIRE(ptrace(PT_TO_SCE, fpid, (caddr_t)1, 0) == 0);
ATF_REQUIRE(ptrace(PT_SYSCALL, fpid, (caddr_t)1, 0) == 0);
/*
* The next stop should be the syscall entry from getpid().
@ -3948,6 +3950,25 @@ ATF_TC_BODY(ptrace__syscall_args, tc)
ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
/*
* The next stop should be the syscall exit from getpid().
*/
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCX);
ATF_REQUIRE(pl.pl_syscall_code == SYS_getpid);
ATF_REQUIRE(ptrace(PT_GET_SC_RET, wpid, (caddr_t)&psr,
sizeof(psr)) != -1);
ATF_REQUIRE(psr.sr_error == 0);
ATF_REQUIRE(psr.sr_retval[0] == wpid);
ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
/*
* The next stop should be the syscall entry from kill().
*/
@ -3966,6 +3987,61 @@ ATF_TC_BODY(ptrace__syscall_args, tc)
ATF_REQUIRE(args[0] == wpid);
ATF_REQUIRE(args[1] == 0);
ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
/*
* The next stop should be the syscall exit from kill().
*/
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCX);
ATF_REQUIRE(pl.pl_syscall_code == SYS_kill);
ATF_REQUIRE(ptrace(PT_GET_SC_RET, wpid, (caddr_t)&psr,
sizeof(psr)) != -1);
ATF_REQUIRE(psr.sr_error == 0);
ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
/*
* The next stop should be the syscall entry from close().
*/
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCE);
ATF_REQUIRE(pl.pl_syscall_code == SYS_close);
ATF_REQUIRE(pl.pl_syscall_narg == 1);
ATF_REQUIRE(ptrace(PT_GET_SC_ARGS, wpid, (caddr_t)args,
sizeof(args)) != -1);
ATF_REQUIRE(args[0] == 3);
ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
/*
* The next stop should be the syscall exit from close().
*/
wpid = waitpid(fpid, &status, 0);
ATF_REQUIRE(wpid == fpid);
ATF_REQUIRE(WIFSTOPPED(status));
ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCX);
ATF_REQUIRE(pl.pl_syscall_code == SYS_close);
ATF_REQUIRE(ptrace(PT_GET_SC_RET, wpid, (caddr_t)&psr,
sizeof(psr)) != -1);
ATF_REQUIRE(psr.sr_error == EBADF);
/* Disable syscall tracing and continue the child to let it exit. */
ATF_REQUIRE(ptrace(PT_GET_EVENT_MASK, fpid, (caddr_t)&events,
sizeof(events)) == 0);