Merging upstream version 6.10.3.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

10 files changed, 134 insertions, 30 deletions

diff --git a/arch/um/os-Linux/drivers/ethertap_kern.c b/arch/um/os-Linux/drivers/ethertap_kern.c
index 3182e759d8..5e5ee40680 100644
--- a/arch/um/os-Linux/drivers/ethertap_kern.c
+++ b/arch/um/os-Linux/drivers/ethertap_kern.c
@@ -63,7 +63,7 @@ const struct net_kern_info ethertap_kern_info = {
 	.write 			= etap_write,
 };
 
-int ethertap_setup(char *str, char **mac_out, void *data)
+static int ethertap_setup(char *str, char **mac_out, void *data)
 {
 	struct ethertap_init *init = data;
 
diff --git a/arch/um/os-Linux/drivers/tuntap_kern.c b/arch/um/os-Linux/drivers/tuntap_kern.c
index adcb6717be..ff022d9cf0 100644
--- a/arch/um/os-Linux/drivers/tuntap_kern.c
+++ b/arch/um/os-Linux/drivers/tuntap_kern.c
@@ -53,7 +53,7 @@ const struct net_kern_info tuntap_kern_info = {
 	.write 			= tuntap_write,
 };
 
-int tuntap_setup(char *str, char **mac_out, void *data)
+static int tuntap_setup(char *str, char **mac_out, void *data)
 {
 	struct tuntap_init *init = data;
 
diff --git a/arch/um/os-Linux/elf_aux.c b/arch/um/os-Linux/elf_aux.c
index 344ac403fb..0a0f91cf4d 100644
--- a/arch/um/os-Linux/elf_aux.c
+++ b/arch/um/os-Linux/elf_aux.c
@@ -13,6 +13,7 @@
 #include <init.h>
 #include <elf_user.h>
 #include <mem_user.h>
+#include "internal.h"
 
 typedef Elf32_auxv_t elf_auxv_t;
 
diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
new file mode 100644
index 0000000000..317fca190c
--- /dev/null
+++ b/arch/um/os-Linux/internal.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_OS_LINUX_INTERNAL_H
+#define __UM_OS_LINUX_INTERNAL_H
+
+/*
+ * elf_aux.c
+ */
+void scan_elf_aux(char **envp);
+
+/*
+ * mem.c
+ */
+void check_tmpexec(void);
+
+/*
+ * skas/process.c
+ */
+void wait_stub_done(int pid);
+
+#endif /* __UM_OS_LINUX_INTERNAL_H */
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index c8a42ecbd7..f98ff79cdb 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -16,6 +16,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <um_malloc.h>
+#include "internal.h"
 
 #define PGD_BOUND (4 * 1024 * 1024)
 #define STACKSIZE (8 * 1024 * 1024)
@@ -102,8 +103,6 @@ static void setup_env_path(void)
 	}
 }
 
-extern void scan_elf_aux( char **envp);
-
 int __init main(int argc, char **argv, char **envp)
 {
 	char **new_argv;
@@ -184,6 +183,11 @@ int __init main(int argc, char **argv, char **envp)
 
 extern void *__real_malloc(int);
 
+/* workaround for -Wmissing-prototypes warnings */
+void *__wrap_malloc(int size);
+void *__wrap_calloc(int n, int size);
+void __wrap_free(void *ptr);
+
 void *__wrap_malloc(int size)
 {
 	void *ret;
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index c6c9495b14..cf44d386f2 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -17,6 +17,7 @@
 #include <init.h>
 #include <kern_util.h>
 #include <os.h>
+#include "internal.h"
 
 /*
  * kasan_map_memory - maps memory from @start with a size of @len.
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 24a403a70a..b11ed66c8b 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -8,6 +8,7 @@
 
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <errno.h>
 #include <signal.h>
 #include <string.h>
@@ -65,25 +66,36 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 
 int signals_enabled;
 #ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
-static int signals_blocked;
-#else
-#define signals_blocked 0
+static int signals_blocked, signals_blocked_pending;
 #endif
 static unsigned int signals_pending;
 static unsigned int signals_active = 0;
 
-void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
+static void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
 {
 	int enabled = signals_enabled;
 
-	if ((signals_blocked || !enabled) && (sig == SIGIO)) {
+#ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
+	if ((signals_blocked ||
+	     __atomic_load_n(&signals_blocked_pending, __ATOMIC_SEQ_CST)) &&
+	    (sig == SIGIO)) {
+		/* increment so unblock will do another round */
+		__atomic_add_fetch(&signals_blocked_pending, 1,
+				   __ATOMIC_SEQ_CST);
+		return;
+	}
+#endif
+
+	if (!enabled && (sig == SIGIO)) {
 		/*
 		 * In TT_MODE_EXTERNAL, need to still call time-travel
-		 * handlers unless signals are also blocked for the
-		 * external time message processing. This will mark
-		 * signals_pending by itself (only if necessary.)
+		 * handlers. This will mark signals_pending by itself
+		 * (only if necessary.)
+		 * Note we won't get here if signals are hard-blocked
+		 * (which is handled above), in that case the hard-
+		 * unblock will handle things.
 		 */
-		if (!signals_blocked && time_travel_mode == TT_MODE_EXTERNAL)
+		if (time_travel_mode == TT_MODE_EXTERNAL)
 			sigio_run_timetravel_handlers();
 		else
 			signals_pending |= SIGIO_MASK;
@@ -108,7 +120,7 @@ static void timer_real_alarm_handler(mcontext_t *mc)
 	timer_handler(SIGALRM, NULL, &regs);
 }
 
-void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+static void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
 {
 	int enabled;
 
@@ -380,33 +392,99 @@ int um_set_signals_trace(int enable)
 #ifdef UML_CONFIG_UML_TIME_TRAVEL_SUPPORT
 void mark_sigio_pending(void)
 {
+	/*
+	 * It would seem that this should be atomic so
+	 * it isn't a read-modify-write with a signal
+	 * that could happen in the middle, losing the
+	 * value set by the signal.
+	 *
+	 * However, this function is only called when in
+	 * time-travel=ext simulation mode, in which case
+	 * the only signal ever pending is SIGIO, which
+	 * is blocked while this can be called, and the
+	 * timer signal (SIGALRM) cannot happen.
+	 */
 	signals_pending |= SIGIO_MASK;
 }
 
 void block_signals_hard(void)
 {
-	if (signals_blocked)
-		return;
-	signals_blocked = 1;
+	signals_blocked++;
 	barrier();
 }
 
 void unblock_signals_hard(void)
 {
+	static bool unblocking;
+
 	if (!signals_blocked)
+		panic("unblocking signals while not blocked");
+
+	if (--signals_blocked)
 		return;
-	/* Must be set to 0 before we check the pending bits etc. */
-	signals_blocked = 0;
+	/*
+	 * Must be set to 0 before we check pending so the
+	 * SIGIO handler will run as normal unless we're still
+	 * going to process signals_blocked_pending.
+	 */
 	barrier();
 
-	if (signals_pending && signals_enabled) {
-		/* this is a bit inefficient, but that's not really important */
-		block_signals();
-		unblock_signals();
-	} else if (signals_pending & SIGIO_MASK) {
-		/* we need to run time-travel handlers even if not enabled */
-		sigio_run_timetravel_handlers();
+	/*
+	 * Note that block_signals_hard()/unblock_signals_hard() can be called
+	 * within the unblock_signals()/sigio_run_timetravel_handlers() below.
+	 * This would still be prone to race conditions since it's actually a
+	 * call _within_ e.g. vu_req_read_message(), where we observed this
+	 * issue, which loops. Thus, if the inner call handles the recorded
+	 * pending signals, we can get out of the inner call with the real
+	 * signal hander no longer blocked, and still have a race. Thus don't
+	 * handle unblocking in the inner call, if it happens, but only in
+	 * the outermost call - 'unblocking' serves as an ownership for the
+	 * signals_blocked_pending decrement.
+	 */
+	if (unblocking)
+		return;
+	unblocking = true;
+
+	while (__atomic_load_n(&signals_blocked_pending, __ATOMIC_SEQ_CST)) {
+		if (signals_enabled) {
+			/* signals are enabled so we can touch this */
+			signals_pending |= SIGIO_MASK;
+			/*
+			 * this is a bit inefficient, but that's
+			 * not really important
+			 */
+			block_signals();
+			unblock_signals();
+		} else {
+			/*
+			 * we need to run time-travel handlers even
+			 * if not enabled
+			 */
+			sigio_run_timetravel_handlers();
+		}
+
+		/*
+		 * The decrement of signals_blocked_pending must be atomic so
+		 * that the signal handler will either happen before or after
+		 * the decrement, not during a read-modify-write:
+		 *  - If it happens before, it can increment it and we'll
+		 *    decrement it and do another round in the loop.
+		 *  - If it happens after it'll see 0 for both signals_blocked
+		 *    and signals_blocked_pending and thus run the handler as
+		 *    usual (subject to signals_enabled, but that's unrelated.)
+		 *
+		 * Note that a call to unblock_signals_hard() within the calls
+		 * to unblock_signals() or sigio_run_timetravel_handlers() above
+		 * will do nothing due to the 'unblocking' state, so this cannot
+		 * underflow as the only one decrementing will be the outermost
+		 * one.
+		 */
+		if (__atomic_sub_fetch(&signals_blocked_pending, 1,
+				       __ATOMIC_SEQ_CST) < 0)
+			panic("signals_blocked_pending underflow");
 	}
+
+	unblocking = false;
 }
 #endif
 
diff --git a/arch/um/os-Linux/skas/mem.c b/arch/um/os-Linux/skas/mem.c
index 953fb10f3f..1f9c1bffc3 100644
--- a/arch/um/os-Linux/skas/mem.c
+++ b/arch/um/os-Linux/skas/mem.c
@@ -17,11 +17,10 @@
 #include <skas.h>
 #include <sysdep/ptrace.h>
 #include <sysdep/stub.h>
+#include "../internal.h"
 
 extern char batch_syscall_stub[], __syscall_stub_start[];
 
-extern void wait_stub_done(int pid);
-
 static inline unsigned long *check_init_stack(struct mm_id * mm_idp,
 					      unsigned long *stack)
 {
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 1f5c3f2523..41a288dcfc 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -23,6 +23,7 @@
 #include <skas.h>
 #include <sysdep/stub.h>
 #include <linux/threads.h>
+#include "../internal.h"
 
 int is_skas_winch(int pid, int fd, void *data)
 {
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index 8b0e98ab84..89ad9f4f86 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -20,10 +20,12 @@
 #include <asm/unistd.h>
 #include <init.h>
 #include <os.h>
+#include <kern_util.h>
 #include <mem_user.h>
 #include <ptrace_user.h>
 #include <registers.h>
 #include <skas.h>
+#include "internal.h"
 
 static void ptrace_child(void)
 {
@@ -221,8 +223,6 @@ static void __init check_ptrace(void)
 	check_sysemu();
 }
 
-extern void check_tmpexec(void);
-
 static void __init check_coredump_limit(void)
 {
 	struct rlimit lim;