Merge tag 'uml-for-linux-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

Pull UML updates from Johannes Berg:
 "The only really new thing is the long-standing seccomp work
  (originally from 2021!). Wven if it still isn't enabled by default due
  to security concerns it can still be used e.g. for tests.

   - remove obsolete network transports

   - remove PCI IO port support

   - start adding seccomp-based process handling instead of ptrace"

* tag 'uml-for-linux-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux: (29 commits)
  um: remove "extern" from implementation of sigchld_handler
  um: fix unused variable warning
  um: fix SECCOMP 32bit xstate register restore
  um: pass FD for memory operations when needed
  um: Add SECCOMP support detection and initialization
  um: Implement kernel side of SECCOMP based process handling
  um: Track userspace children dying in SECCOMP mode
  um: Add helper functions to get/set state for SECCOMP
  um: Add stub side of SECCOMP/futex based process handling
  um: Move faultinfo extraction into userspace routine
  um: vector: Use mac_pton() for MAC address parsing
  um: vector: Clean up and modernize log messages
  um: chan_kern: use raw spinlock for irqs_to_free_lock
  MAINTAINERS: remove obsolete file entry in TUN/TAP DRIVER
  um: Fix tgkill compile error on old host OSes
  um: stop using PCI port I/O
  um: Remove legacy network transport infrastructure
  um: vector: Eliminate the dependency on uml_net
  um: Remove obsolete legacy network transports
  um/asm: Replace "REP; NOP" with PAUSE mnemonic
  ...

1 files changed, 18 insertions, 1 deletions

diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index e71e5b4878d1..11f07f498270 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -29,6 +29,7 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *, void *mc) =
 	[SIGBUS]	= relay_signal,
 	[SIGSEGV]	= segv_handler,
 	[SIGIO]		= sigio_handler,
+	[SIGCHLD]	= sigchld_handler,
 };
 
 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
@@ -44,7 +45,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 	}
 
 	/* enable signals if sig isn't IRQ signal */
-	if ((sig != SIGIO) && (sig != SIGWINCH))
+	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGCHLD))
 		unblock_signals_trace();
 
 	(*sig_info[sig])(sig, si, &r, mc);
@@ -64,6 +65,9 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGALRM_BIT 1
 #define SIGALRM_MASK (1 << SIGALRM_BIT)
 
+#define SIGCHLD_BIT 2
+#define SIGCHLD_MASK (1 << SIGCHLD_BIT)
+
 int signals_enabled;
 #if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 static int signals_blocked, signals_blocked_pending;
@@ -102,6 +106,11 @@ static void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
 		return;
 	}
 
+	if (!enabled && (sig == SIGCHLD)) {
+		signals_pending |= SIGCHLD_MASK;
+		return;
+	}
+
 	block_signals_trace();
 
 	sig_handler_common(sig, si, mc);
@@ -181,6 +190,8 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
 
 	[SIGIO] = sig_handler,
 	[SIGWINCH] = sig_handler,
+	/* SIGCHLD is only actually registered in seccomp mode. */
+	[SIGCHLD] = sig_handler,
 	[SIGALRM] = timer_alarm_handler,
 
 	[SIGUSR1] = sigusr1_handler,
@@ -309,6 +320,12 @@ void unblock_signals(void)
 		if (save_pending & SIGIO_MASK)
 			sig_handler_common(SIGIO, NULL, NULL);
 
+		if (save_pending & SIGCHLD_MASK) {
+			struct uml_pt_regs regs = {};
+
+			sigchld_handler(SIGCHLD, NULL, &regs, NULL);
+		}
+
 		/* Do not reenter the handler */
 
 		if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK)))