From c81bdac897a74f581605f3b4c7b4daccfb77a0c0 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Wed, 29 May 2024 11:06:15 -0300
Subject: [PATCH] signals: handle SIGBUS, SIGSEGV, SIGILL etc

---
 kernel-src/arch/x86-64/cpu.c | 18 ++++++++++++++++++
 kernel-src/arch/x86-64/mmu.c | 10 +++++++++-
 kernel-src/mm/vmm.c          |  5 +++--
 kernel-src/sys/signal.c      |  4 +++-
 4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/kernel-src/arch/x86-64/cpu.c b/kernel-src/arch/x86-64/cpu.c
index b3602e1a..b4275685 100644
--- a/kernel-src/arch/x86-64/cpu.c
+++ b/kernel-src/arch/x86-64/cpu.c
@@ -7,6 +7,21 @@
 #define EFER_SYSCALLENABLE 1
 
 void arch_syscall_entry();
+static void illisr(isr_t *self, context_t *ctx) {
+	if (ARCH_CONTEXT_ISUSER(ctx)) {
+		signal_signalthread(_cpu()->thread, SIGILL, true);
+	} else {
+		_panic("Invalid Opcode", ctx);
+	}
+}
+
+static void div0isr(isr_t *self, context_t *ctx) {
+	if (ARCH_CONTEXT_ISUSER(ctx)) {
+		signal_signalthread(_cpu()->thread, SIGFPE, true);
+	} else {
+		_panic("Division by 0", ctx);
+	}
+}
 
 void cpu_initstate() {
 	arch_apic_initap();
@@ -49,4 +64,7 @@ void cpu_initstate() {
 		"mov %%rax, %%cr0;"
 		: : : "rax"
 	);
+
+	interrupt_register(0, div0isr, NULL, IPL_IGNORE);
+	interrupt_register(6, illisr, NULL, IPL_IGNORE);
 }
diff --git a/kernel-src/arch/x86-64/mmu.c b/kernel-src/arch/x86-64/mmu.c
index 00040eed..09c075ec 100644
--- a/kernel-src/arch/x86-64/mmu.c
+++ b/kernel-src/arch/x86-64/mmu.c
@@ -278,10 +278,17 @@ static void pfisr(isr_t *self, context_t *ctx) {
 		if (ARCH_CONTEXT_ISUSER(ctx))
 			signal_signalthread(_cpu()->thread, SIGSEGV, true);
 		else
-			_panic("Page fault", ctx);
+			_panic("Page Fault", ctx);
 	}
 }
 
+static void gpfisr(isr_t *self, context_t *ctx) {
+	if (ARCH_CONTEXT_ISUSER(ctx))
+		signal_signalthread(_cpu()->thread, SIGSEGV, true);
+	else
+		_panic("General Protection Fault", ctx);
+}
+
 void arch_mmu_init() {
 	template = pmm_allocpage(PMM_SECTION_DEFAULT);
 	__assert(template);
@@ -326,6 +333,7 @@ void arch_mmu_init() {
 
 void arch_mmu_apswitch() {
 	arch_mmu_switch(FROM_HHDM(template));
+	interrupt_register(13, gpfisr, NULL, IPL_IGNORE);
 	interrupt_register(14, pfisr, NULL, IPL_IGNORE);
 	interrupt_register(0xfe, arch_mmu_tlbipi, ARCH_EOI, IPL_IGNORE);
 }
diff --git a/kernel-src/mm/vmm.c b/kernel-src/mm/vmm.c
index dd092518..a6057710 100644
--- a/kernel-src/mm/vmm.c
+++ b/kernel-src/mm/vmm.c
@@ -363,8 +363,9 @@ bool vmm_pagefault(void *addr, bool user, int actions) {
 				page_t *res = NULL;
 				int error = vmmcache_getpage(range->vnode, range->offset + mapoffset, &res);
 				if (error == ENXIO) {
-					// TODO if error returned == ENXIO, raise an urgent SIGBUS on the calling thread
-					__assert(!"TODO: sigbus");
+					// address is past the last page of the file
+					signal_signalthread(_cpu()->thread, SIGBUS, true);
+					status = true;
 				} else if (error) {
 					printf("vmm: error on vmmcache_getpage(): %d\n", error);
 					status = false;
diff --git a/kernel-src/sys/signal.c b/kernel-src/sys/signal.c
index d2a18048..f5b65174 100644
--- a/kernel-src/sys/signal.c
+++ b/kernel-src/sys/signal.c
@@ -325,6 +325,7 @@ bool signal_check(struct thread_t *thread, context_t *context, bool syscall, uin
 					goto leave;
 				}
 				// if not, just sleep. the sigcont won't be sent until THREAD_LEAVE and preparesleep is protecting it from a lost wakeup
+				context_t savecontext = *context; // save context as it could be overwritten if, for example, its the thread->context one
 				sched_preparesleep(false);
 				thread->signals.stopped = true;
 				THREAD_LEAVE(thread);
@@ -334,6 +335,7 @@ bool signal_check(struct thread_t *thread, context_t *context, bool syscall, uin
 				// make sure a SIGCONT happened
 				__assert(SIGNAL_GET(&thread->signals.pending, SIGCONT));
 				__assert(thread->signals.stopped == false);
+				*context = savecontext; // restore saved context
 				// the stopped variable is already set by the signaling function
 				// see if theres any other signal to deal with (such as the SIGCONT handler)
 				return true;
@@ -352,7 +354,7 @@ bool signal_check(struct thread_t *thread, context_t *context, bool syscall, uin
 		// get where in memory to put the frame
 		void *stack = altstack ? altstack : (void *)CTX_SP(context);
 		#if ARCH_SIGNAL_STACK_GROWS_DOWNWARDS == 1
-		stack = (void *)(((uintptr_t)stack - ARCH_SIGNAL_REDZONE_SIZE - sizeof(sigframe_t)) & ~0xf);
+		stack = (void *)(((uintptr_t)stack - ARCH_SIGNAL_REDZONE_SIZE - sizeof(sigframe_t)) & ~0xfl);
 		#else
 			#error unsupported
 		#endif