From da1bf45572b76900e3219f2c2c08942d655bfe4c Mon Sep 17 00:00:00 2001
From: Lauri Kasanen <cand@gmx.com>
Date: Thu, 27 May 2021 15:05:38 +0300
Subject: [PATCH] Start on kvm side

---
 main.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/main.c b/main.c
index daa48ee..8550e4e 100644
--- a/main.c
+++ b/main.c
@@ -16,6 +16,7 @@
 
 #define _GNU_SOURCE
 
+#include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
 #include <linux/kvm.h>
@@ -25,11 +26,14 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #define MAXDUMPS 10
+#define RAMSIZE (64 * 1024 * 1024)
+#define PROGSTART 0x20000000
 
 static void nukenewline(char buf[]) {
 	unsigned i;
@@ -184,10 +188,15 @@ int main(int argc, char **argv) {
 	};
 	const char opts[] = "i:g:f:s:l:d:t:h";
 
-	int kvm;
+	struct kvm_run *run;
+	struct kvm_regs regs;
+	struct kvm_sregs sregs;
+	int kvm, vmfd, vcpu;
 	FILE *binary = NULL, *trace = NULL;
 	char dumps[MAXDUMPS][PATH_MAX];
 	unsigned num_dumps = 0;
+	uint8_t *ram, *progmem;
+	const char *binpath;
 
 	while (1) {
 		const int c = getopt_long(argc, argv, opts, longopts, NULL);
@@ -206,6 +215,8 @@ int main(int argc, char **argv) {
 					printf("Failed to open %s\n", optarg);
 					return 1;
 				}
+
+				binpath = strdup(optarg);
 			break;
 			case 'g':
 				parseregs(optarg, 1);
@@ -252,12 +263,24 @@ int main(int argc, char **argv) {
 		help(argv[0]);
 	}
 
+	// Yes, we're frugal
+	if (posix_memalign(&ram, 64 * 1024, RAMSIZE))
+		abort();
+	memset(ram, 0, RAMSIZE);
+
 	fseek(binary, 0, SEEK_END);
 	const unsigned binlen = ftell(binary);
 	rewind(binary);
 
 	printf("Loading binary %u bytes\n", binlen); // TODO
 
+	if (posix_memalign(&progmem, 64 * 1024, binlen))
+		abort();
+
+	if (fread(progmem, binlen, 1, binary) != 1)
+		abort();
+	fclose(binary);
+
 	kvm = open("/dev/kvm", O_RDWR | O_CLOEXEC);
 	if (kvm < 0) {
 		printf("Failed to open kvm, perhaps you lack permissions?\n");
@@ -268,6 +291,59 @@ int main(int argc, char **argv) {
 	ret = ioctl(kvm, KVM_GET_API_VERSION, NULL);
 	if (ret == -1 || ret != 12) abort();
 
+	ret = ioctl(kvm, KVM_CHECK_EXTENSION, KVM_CAP_PPC_GUEST_DEBUG_SSTEP);
+	if (ret == -1 || !ret) {
+		printf("This system lacks single-stepping!\n");
+		return 1;
+	}
+
+	vmfd = ioctl(kvm, KVM_CREATE_VM, (unsigned long)0);
+
+	struct kvm_userspace_memory_region region = {
+		.slot = 0,
+		.guest_phys_addr = 0,
+		.memory_size = RAMSIZE,
+		.userspace_addr = ram,
+		.flags = 0
+	};
+	ioctl(vmfd, KVM_SET_USER_MEMORY_REGION, &region);
+
+	region.slot = 1;
+	region.guest_phys_addr = PROGSTART;
+	region.memory_size = binlen;
+	region.userspace_addr = progmem;
+	region.flags = KVM_MEM_READONLY;
+	ioctl(vmfd, KVM_SET_USER_MEMORY_REGION, &region);
+
+	vcpu = ioctl(vmfd, KVM_CREATE_VCPU, (unsigned long)0);
+	const unsigned vcpulen = ioctl(kvm, KVM_GET_VCPU_MMAP_SIZE, NULL);
+
+	run = mmap(NULL, vcpulen, PROT_READ | PROT_WRITE, MAP_SHARED, vcpu, 0);
+
+	if (ioctl(vcpu, KVM_GET_SREGS, &sregs) == -1)
+		abort();
+	if (ioctl(vcpu, KVM_SET_SREGS, &sregs) == -1)
+		abort();
+
+	if (ioctl(vcpu, KVM_SET_REGS, &regs) == -1)
+		abort();
+
+	const struct kvm_guest_debug dbg = {
+		.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
+	};
+	if (ioctl(vcpu, KVM_SET_GUEST_DEBUG, &dbg) == -1)
+		abort();
+
+	// Runtime
+	while (1) {
+		if (ioctl(vcpu, KVM_RUN, NULL) == -1)
+			abort();
+		printf("Exited because %u\n", run->exit_reason);
+	}
+
 	close(kvm);
+	free(progmem);
+	free(ram);
+	free((char *) binpath);
 	return 0;
 }
-- 
2.30.2