git: fd5faa5629ae - main - ptrace(2): PT_SET_SC_RET request
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Date: Thu, 16 Jul 2026 22:41:42 UTC
The branch main has been updated by kib:
URL: https://cgit.FreeBSD.org/src/commit/?id=fd5faa5629aed98f4daee84063da3494c4d1eee9
commit fd5faa5629aed98f4daee84063da3494c4d1eee9
Author: Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2026-07-15 02:23:17 +0000
Commit: Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-07-16 22:22:55 +0000
ptrace(2): PT_SET_SC_RET request
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D58247
---
sys/compat/freebsd32/freebsd32_misc.c | 19 +++++++++++++++++++
sys/kern/subr_syscall.c | 12 ++++++++----
sys/kern/sys_process.c | 24 ++++++++++++++++++++++++
sys/sys/proc.h | 1 +
sys/sys/ptrace.h | 3 ++-
5 files changed, 54 insertions(+), 5 deletions(-)
diff --git a/sys/compat/freebsd32/freebsd32_misc.c b/sys/compat/freebsd32/freebsd32_misc.c
index e4a4f256feb4..e07000015d54 100644
--- a/sys/compat/freebsd32/freebsd32_misc.c
+++ b/sys/compat/freebsd32/freebsd32_misc.c
@@ -1005,6 +1005,16 @@ ptrace_sc_ret_to32(const struct ptrace_sc_ret *psr,
psr32->sr_error = psr->sr_error;
}
+static void
+ptrace_sc_ret32_to_ret(const struct ptrace_sc_ret32 *psr32,
+ struct ptrace_sc_ret *psr)
+{
+ bzero(psr, sizeof(*psr));
+ psr->sr_retval[0] = psr32->sr_retval[0];
+ psr->sr_retval[1] = psr32->sr_retval[1];
+ psr->sr_error = psr32->sr_error;
+}
+
int
freebsd32_ptrace(struct thread *td, struct freebsd32_ptrace_args *uap)
{
@@ -1051,6 +1061,15 @@ freebsd32_ptrace(struct thread *td, struct freebsd32_ptrace_args *uap)
case PT_GET_SC_ARGS:
case PT_GET_SC_RET:
break;
+ case PT_SET_SC_RET:
+ if (uap->data != sizeof(r32.psr)) {
+ error = EINVAL;
+ } else {
+ error = copyin(uap->addr, &r32.psr, sizeof(r32.psr));
+ if (error == 0)
+ ptrace_sc_ret32_to_ret(&r32.psr, &r.psr);
+ }
+ break;
case PT_LWPINFO:
if (uap->data > sizeof(r32.pl))
return (EINVAL);
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index 660170cc7a5f..9997a6b638f7 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -66,10 +66,11 @@ syscallenter(struct thread *td)
if (__predict_false(td->td_cowgen != atomic_load_int(&p->p_cowgen)))
thread_cow_update(td);
traced = (p->p_flag & P_TRACED) != 0;
- if (__predict_false(traced || td->td_dbgflags & TDB_USERWR)) {
+ if (__predict_false(traced || (td->td_dbgflags & (TDB_USERWR |
+ TDB_SET_SC_RET)) != 0)) {
PROC_LOCK(p);
MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0);
- td->td_dbgflags &= ~TDB_USERWR;
+ td->td_dbgflags &= ~(TDB_USERWR | TDB_SET_SC_RET);
if (traced)
td->td_dbgflags |= TDB_SCE;
PROC_UNLOCK(p);
@@ -97,7 +98,10 @@ syscallenter(struct thread *td)
ptracestop((td), SIGTRAP, NULL);
PROC_UNLOCK(p);
- if ((td->td_dbgflags & TDB_USERWR) != 0) {
+ if ((td->td_dbgflags & TDB_SET_SC_RET) != 0) {
+ error = td->td_errno;
+ goto retval;
+ } else if ((td->td_dbgflags & TDB_USERWR) != 0) {
/*
* Reread syscall number and arguments if debugger
* modified registers or memory.
@@ -201,7 +205,7 @@ syscallenter(struct thread *td)
td->td_retval[1]);
if (__predict_false(traced)) {
PROC_LOCK(p);
- td->td_dbgflags &= ~(TDB_SCE | TDB_BOUNDARY);
+ td->td_dbgflags &= ~(TDB_SCE | TDB_BOUNDARY | TDB_SET_SC_RET);
PROC_UNLOCK(p);
}
(p->p_sysent->sv_set_syscall_retval)(td, error);
diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index e10d1fc4b8be..d3f8e4c81669 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -752,6 +752,12 @@ sys_ptrace(struct thread *td, struct ptrace_args *uap)
case PT_GET_SC_ARGS:
case PT_GET_SC_RET:
break;
+ case PT_SET_SC_RET:
+ if (uap->data != sizeof(r.psr))
+ error = EINVAL;
+ else
+ error = copyin(uap->addr, &r.psr, sizeof(r.psr));
+ break;
case PT_GETREGS:
bzero(&r.reg, sizeof(r.reg));
break;
@@ -1340,6 +1346,24 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
psr->sr_retval[1]);
break;
+ case PT_SET_SC_RET:
+ if ((td2->td_dbgflags & TDB_SCE) == 0
+#ifdef COMPAT_FREEBSD32
+ || (wrap32 && !safe)
+#endif
+ ) {
+ error = EINVAL;
+ break;
+ }
+ psr = addr;
+ td2->td_errno = psr->sr_error;
+ if (td2->td_errno == 0) {
+ td2->td_retval[0] = psr->sr_retval[0];
+ td2->td_retval[1] = psr->sr_retval[1];
+ }
+ td2->td_dbgflags |= TDB_SET_SC_RET;
+ break;
+
case PT_STEP:
case PT_CONTINUE:
case PT_TO_SCE:
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 6736fa5bb5f9..9b98550b9f8c 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -531,6 +531,7 @@ enum {
#define TDB_BOUNDARY 0x00008000 /* ptracestop() at boundary */
#define TDB_COREDUMPREQ 0x00010000 /* Coredump request */
#define TDB_SCREMOTEREQ 0x00020000 /* Remote syscall request */
+#define TDB_SET_SC_RET 0x00040000 /* PT_SET_SC_RET applied */
/*
* "Private" flags kept in td_pflags:
diff --git a/sys/sys/ptrace.h b/sys/sys/ptrace.h
index 2ef52b22044c..2aa82ce07a1d 100644
--- a/sys/sys/ptrace.h
+++ b/sys/sys/ptrace.h
@@ -85,6 +85,7 @@
#define PT_GETREGSET 42 /* Get a target register set */
#define PT_SETREGSET 43 /* Set a target register set */
#define PT_SC_REMOTE 44 /* Execute a syscall */
+#define PT_SET_SC_RET 45 /* Set (fake) syscall results */
#define PT_FIRSTMACH 64 /* for machine-specific requests */
#define PT_LASTMACH 127
@@ -166,7 +167,7 @@ struct ptrace_lwpinfo32 {
};
#endif
-/* Argument structure for PT_GET_SC_RET. */
+/* Argument structure for PT_GET_SC_RET and PT_SET_SC_RET. */
struct ptrace_sc_ret {
syscallarg_t sr_retval[2]; /* Only valid if sr_error == 0. */
int sr_error;