syscall log: support for selective syscall tracing

kernel-src/arch/x86-64/archctl.c

@@ -1,3 +1,4 @@
+#include <arch/cpu.h>
 #include <kernel/syscalls.h>
 #include <arch/msr.h>
 #include <errno.h>
@@ -6,6 +7,11 @@
 #define ARCH_CTL_SET_FSBASE 1
 #define ARCH_CTL_GET_GSBASE 2
 #define ARCH_CTL_GET_FSBASE 3
+#define ARCH_CTL_SET_SYSTRACE 4
+
+#define ARCH_CTL_SYSTRACE_OFF 0
+#define ARCH_CTL_SYSTRACE_SELF 1
+#define ARCH_CTL_SYSTRACE_ALL 2
 
 static inline int copy_u64_to_user(void *ptr, uint64_t v) {
 	return usercopy_touser(ptr, &v, sizeof(v));
@@ -36,6 +42,28 @@ syscallret_t syscall_archctl(context_t *context, int func, void *arg) {
 		case ARCH_CTL_GET_FSBASE:
 			ret.errno = copy_u64_to_user(arg, rdmsr(MSR_FSBASE));
 			break;
+		case ARCH_CTL_SET_SYSTRACE:
+#ifdef SYSCALL_LOGGING
+			switch ((uint64_t)arg) {
+				case ARCH_CTL_SYSTRACE_OFF:
+					current_thread()->proc->flags &= ~(PROC_FLAG_SYSTRACE | PROC_FLAG_SYSTRACE_SELF);
+					break;
+				case ARCH_CTL_SYSTRACE_SELF:
+					current_thread()->proc->flags |= PROC_FLAG_SYSTRACE | PROC_FLAG_SYSTRACE_SELF;
+					break;
+				case ARCH_CTL_SYSTRACE_ALL:
+					current_thread()->proc->flags |= PROC_FLAG_SYSTRACE;
+					current_thread()->proc->flags &= ~PROC_FLAG_SYSTRACE_SELF;
+					break;
+				default:
+					ret.errno = EINVAL;
+					break;
+			}
+#else
+			// signal that syscall logging is not supported
+			ret.errno = ENOTSUP;
+#endif
+			break;
 		default:
 			ret.errno = EINVAL;
 			break;

kernel-src/arch/x86-64/syscalllog.c

@@ -5,6 +5,9 @@
 
 #ifdef SYSCALL_LOGGING
 
+void arch_interrupt_disable();
+void arch_interrupt_enable();
+
 #define SYSCALL_COUNT 99
 #define LOGSTR(x) arch_e9_puts(x)
 
@@ -225,6 +228,9 @@ __attribute__((no_caller_saved_registers)) void arch_syscall_log(int syscall, ui
 
 	thread_t *thread = current_thread();
 	proc_t *proc = thread->proc;
+	if (!(proc->flags & PROC_FLAG_SYSTRACE))
+		return;
+
 	snprintf(argbuff, 768, syscall < SYSCALL_COUNT ? args[syscall] : "N/A", a1, a2, a3, a4, a5, a6);
 	snprintf(printbuff, 1024, "\e[92msyscall: pid %d tid %d: %s: %s (%lu cached pages, %lu free pages)\n\e[0m", proc->pid, thread->tid, syscall < SYSCALL_COUNT ? name[syscall] : "invalid syscall", argbuff, vmmcache_cachedpages, freepagecount);
 
@@ -242,6 +248,8 @@ __attribute__((no_caller_saved_registers)) void arch_syscall_log_return(uint64_t
 
 	thread_t *thread = current_thread();
 	proc_t *proc = thread->proc;
+	if (!(proc->flags & PROC_FLAG_SYSTRACE))
+		return;
 
 	snprintf(printbuff, 1024, "\e[94msyscall return: pid %d tid %d: %lu %s (%lu cached pages, %lu free pages)\n\e[0m", proc->pid, thread->tid, ret, strerror(errno), vmmcache_cachedpages, freepagecount);
 	arch_interrupt_disable();

kernel-src/include/kernel/proc.h

@@ -16,6 +16,9 @@
 #define PROC_STATE_NORMAL 0
 #define PROC_STATE_ZOMBIE 1
 
+#define PROC_FLAG_SYSTRACE (1 << 0)
+#define PROC_FLAG_SYSTRACE_SELF (1 << 1)
+
 typedef struct proc_t {
 	mutex_t mutex;
 	int refcount;

kernel-src/sys/syscalls/fork.c

@@ -50,6 +50,9 @@ syscallret_t syscall_fork(context_t *ctx) {
 	nproc->root = proc_get_root();
 	nproc->cwd = proc_get_cwd();
 	nproc->threadlist = nthread;
+	if (proc->flags & PROC_FLAG_SYSTRACE && !(proc->flags & PROC_FLAG_SYSTRACE_SELF))
+		nproc->flags |= PROC_FLAG_SYSTRACE;
+
 	nthread->procnext = NULL;
 
 	ARCH_CONTEXT_THREADSAVE(nthread, ctx);