diff --git a/covpreproc.c b/covpreproc.c
index af9c637..c8d570e 100644
--- a/covpreproc.c
+++ b/covpreproc.c
@@ -60,38 +60,38 @@ size_t count_block_bytes(FILE *f) {
 
 int is_cond_jump(const char *s) {
     s += strspn(s, " \t");
-    int found = !strncasecmp(s, "jo", 2)
-                || !strncasecmp(s, "jno", 3)
-                || !strncasecmp(s, "js", 2)
-                || !strncasecmp(s, "jns", 3)
-                || !strncasecmp(s, "je", 2)
-                || !strncasecmp(s, "jne", 3)
-                || !strncasecmp(s, "jz", 2)
-                || !strncasecmp(s, "jnz", 3)
-                || !strncasecmp(s, "jb", 2)
-                || !strncasecmp(s, "jnb", 3)
-                || !strncasecmp(s, "jc", 2)
-                || !strncasecmp(s, "jnc", 3)
-                || !strncasecmp(s, "jae", 3)
-                || !strncasecmp(s, "jnae", 4)
-                || !strncasecmp(s, "jbe", 3)
-                || !strncasecmp(s, "jna", 3)
-                || !strncasecmp(s, "ja", 2)
-                || !strncasecmp(s, "jnbe", 4)
-                || !strncasecmp(s, "jl", 2)
-                || !strncasecmp(s, "jnge", 4)
-                || !strncasecmp(s, "jge", 3)
-                || !strncasecmp(s, "jnl", 3)
-                || !strncasecmp(s, "jle", 3)
-                || !strncasecmp(s, "jng", 3)
-                || !strncasecmp(s, "jg",2)
-                || !strncasecmp(s, "jnle", 4)
-                || !strncasecmp(s, "jp", 2)
-                || !strncasecmp(s, "jpe", 3)
-                || !strncasecmp(s, "jnp", 3)
-                || !strncasecmp(s, "jpo", 3)
-                || !strncasecmp(s, "jcxz", 4)
-                || !strncasecmp(s, "jecxz", 5);
+    int found = !strncmp(s, "jo", 2)
+                || !strncmp(s, "jno", 3)
+                || !strncmp(s, "js", 2)
+                || !strncmp(s, "jns", 3)
+                || !strncmp(s, "je", 2)
+                || !strncmp(s, "jne", 3)
+                || !strncmp(s, "jz", 2)
+                || !strncmp(s, "jnz", 3)
+                || !strncmp(s, "jb", 2)
+                || !strncmp(s, "jnb", 3)
+                || !strncmp(s, "jc", 2)
+                || !strncmp(s, "jnc", 3)
+                || !strncmp(s, "jae", 3)
+                || !strncmp(s, "jnae", 4)
+                || !strncmp(s, "jbe", 3)
+                || !strncmp(s, "jna", 3)
+                || !strncmp(s, "ja", 2)
+                || !strncmp(s, "jnbe", 4)
+                || !strncmp(s, "jl", 2)
+                || !strncmp(s, "jnge", 4)
+                || !strncmp(s, "jge", 3)
+                || !strncmp(s, "jnl", 3)
+                || !strncmp(s, "jle", 3)
+                || !strncmp(s, "jng", 3)
+                || !strncmp(s, "jg",2)
+                || !strncmp(s, "jnle", 4)
+                || !strncmp(s, "jp", 2)
+                || !strncmp(s, "jpe", 3)
+                || !strncmp(s, "jnp", 3)
+                || !strncmp(s, "jpo", 3)
+                || !strncmp(s, "jcxz", 4)
+                || !strncmp(s, "jecxz", 5);
     return found;
 }
 
diff --git a/makefile b/makefile
index 29ec28c..c92c369 100644
--- a/makefile
+++ b/makefile
@@ -1,7 +1,7 @@
 FASM=fasm
 CC=gcc
 WARNINGS=-Wall -Wextra -Wduplicated-cond -Wduplicated-branches -Wlogical-op -Wrestrict -Wnull-dereference -Wjump-misses-init -Wshadow -Wformat=2 -Wswitch -Wswitch-enum #-Wconversion -Wsign-conversion
-CFLAGS=$(WARNINGS) -g -O0 -D_FILE_OFFSET_BITS=64 -Wno-address-of-packed-member -DNDEBUG -masm=intel
+CFLAGS=$(WARNINGS) -std=c99 -g -O0 -D_FILE_OFFSET_BITS=64 -Wno-address-of-packed-member -DNDEBUG -masm=intel -D_POSIX_C_SOURCE=200809L
 CFLAGS_32=$(CFLAGS) -m32
 LDFLAGS=
 LDFLAGS_32=$(LDFLAGS) -m32
@@ -51,10 +51,10 @@ vdisk.o: vdisk.c
 	$(CC) $(CFLAGS_32) -c $<
 
 umka_shell.o: umka_shell.c kolibri.h trace.h syscalls.h
-	$(CC) $(CFLAGS_32) -c $< -std=c99 -D_POSIX_C_SOURCE=2
+	$(CC) $(CFLAGS_32) -c $<
 
 umka_fuse.o: umka_fuse.c kolibri.h
-	$(CC) $(CFLAGS_32) `pkg-config fuse3 --cflags` -c $< -std=gnu99
+	$(CC) $(CFLAGS_32) `pkg-config fuse3 --cflags` -c $<
 
 tools/mkdirrange: tools/mkdirrange.c
 	$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
diff --git a/trace.c b/trace.c
index 05e0e52..5891ed1 100644
--- a/trace.c
+++ b/trace.c
@@ -8,3 +8,11 @@ void trace_begin() {
 void trace_end() {
     trace_lbr_end();
 }
+
+uint32_t trace_pause(void) {
+    return trace_lbr_pause();
+}
+
+void trace_resume(uint32_t value) {
+    trace_lbr_resume(value);
+}
diff --git a/trace.h b/trace.h
index 4456509..84a526e 100644
--- a/trace.h
+++ b/trace.h
@@ -1,7 +1,13 @@
 #ifndef TRACE_H_INCLUDED
 #define TRACE_H_INCLUDED
 
+#define COVERAGE_ON() do { trace_resume(coverage); } while (0)
+
+#define COVERAGE_OFF() do { coverage = trace_pause(); } while (0)
+
 void trace_begin(void);
 void trace_end(void);
+uint32_t trace_pause(void);
+void trace_resume(uint32_t value);
 
 #endif
diff --git a/trace_lbr.c b/trace_lbr.c
index 931331d..664015b 100644
--- a/trace_lbr.c
+++ b/trace_lbr.c
@@ -59,18 +59,23 @@ void handle_sigtrap() {
     wrmsr(MSR_IA32_DEBUGCTLMSR, 3);
 }
 
-void set_eflags_tf(uint32_t tf) {
+uint32_t set_eflags_tf(uint32_t tf) {
+    uint32_t prev;
     __asm__ __inline__ __volatile__ (
         "pushfd;"
         "pop    eax;"
-        "shl    ecx, 8;"    // TF
-        "and    eax, ~(1 << 8);"
+        "ror    eax, 8;"
+        "mov    edx, eax;"
+        "and    edx, 1;"
+        "and    eax, ~1;"
         "or     eax, ecx;"
+        "rol    eax, 8;"
         "push   eax;"
         "popfd"
-        :
+        : "=d"(prev)
         : "c"(tf)
         : "eax", "memory");
+    return prev;
 }
 
 void trace_lbr_begin() {
@@ -92,12 +97,18 @@ void trace_lbr_begin() {
     void *coverage_end_addr = &coverage_end;
     write(covfd, &coverage_begin_addr, 4);
     write(covfd, &coverage_end_addr, 4);
-    set_eflags_tf(1);
 }
 
 void trace_lbr_end() {
-    set_eflags_tf(0);
     wrmsr(MSR_IA32_DEBUGCTLMSR, 0);
     close(msrfd);
     close(covfd);
 }
+
+uint32_t trace_lbr_pause(void) {
+    return set_eflags_tf(0u);
+}
+
+void trace_lbr_resume(uint32_t value) {
+    set_eflags_tf(value);
+}
diff --git a/trace_lbr.h b/trace_lbr.h
index a29a1e0..6064b85 100644
--- a/trace_lbr.h
+++ b/trace_lbr.h
@@ -1,7 +1,11 @@
 #ifndef TRACE_LBR_H_INCLUDED
 #define TRACE_LBR_H_INCLUDED
 
+#include <inttypes.h>
+
 void trace_lbr_begin(void);
 void trace_lbr_end(void);
+uint32_t trace_lbr_pause(void);
+void trace_lbr_resume(uint32_t value);
 
 #endif
diff --git a/umka_shell.c b/umka_shell.c
index 2aa31e7..fc3dc37 100644
--- a/umka_shell.c
+++ b/umka_shell.c
@@ -61,7 +61,7 @@ const char *last_dir = cur_dir;
 bool cur_dir_changed = true;
 
 char cmd_buf[FGETS_BUF_LEN];
-int trace = 0;
+uint32_t coverage = 0;
 
 const char *f70_status_name[] = {
                                  "success",
@@ -177,7 +177,9 @@ const char *get_last_dir(const char *path) {
 
 void prompt() {
     if (cur_dir_changed) {
+        COVERAGE_ON();
         umka_sys_get_cwd(cur_dir, PATH_MAX);
+        COVERAGE_OFF();
         last_dir = get_last_dir(cur_dir);
         cur_dir_changed = false;
     }
@@ -198,7 +200,7 @@ int split_args(char *s, char **argv) {
     return argc;
 }
 
-void umka_disk_list_partitions(disk_t *d) {
+void shell_disk_list_partitions(disk_t *d) {
     for (size_t i = 0; i < d->num_partitions; i++) {
         printf("/%s/%d: ", d->name, i+1);
         if (d->partitions[i]->fs_user_functions == xfs_user_functions) {
@@ -215,7 +217,7 @@ void umka_disk_list_partitions(disk_t *d) {
     }
 }
 
-void umka_disk_add(int argc, char **argv) {
+void shell_disk_add(int argc, char **argv) {
     const char *usage = \
         "usage: disk_add <file> <name> [option]...\n"
         "  <file>           absolute or relative path\n"
@@ -244,10 +246,14 @@ void umka_disk_add(int argc, char **argv) {
 
     void *userdata = vdisk_init(file_name, cache_size);
     if (userdata) {
+        COVERAGE_ON();
         void *vdisk = disk_add(&vdisk_functions, disk_name, userdata, 0);
+        COVERAGE_OFF();
         if (vdisk) {
+            COVERAGE_ON();
             disk_media_changed(vdisk, 1);
-            umka_disk_list_partitions(vdisk);
+            COVERAGE_OFF();
+            shell_disk_list_partitions(vdisk);
             return;
         }
     }
@@ -255,20 +261,22 @@ void umka_disk_add(int argc, char **argv) {
     return;
 }
 
-void umka_disk_del_by_name(const char *name) {
+void shell_disk_del_by_name(const char *name) {
     for(disk_t *d = disk_list.next; d != &disk_list; d = d->next) {
         if (!strcmp(d->name, name)) {
+            COVERAGE_ON();
             disk_del(d);
+            COVERAGE_OFF();
             return;
         }
     }
     printf("umka: can't find disk '%s'\n", name);
 }
 
-void umka_disk_del(int argc, char **argv) {
+void shell_disk_del(int argc, char **argv) {
     (void)argc;
     const char *name = argv[1];
-    umka_disk_del_by_name(name);
+    shell_disk_del_by_name(name);
     return;
 }
 
@@ -277,19 +285,23 @@ void shell_pwd(int argc, char **argv) {
     (void)argv;
     bool quoted = false;
     const char *quote = quoted ? "'" : "";
+    COVERAGE_ON();
     umka_sys_get_cwd(cur_dir, PATH_MAX);
+    COVERAGE_OFF();
     printf("%s%s%s\n", quote, cur_dir, quote);
 }
 
-void umka_set_pixel(int argc, char **argv) {
+void shell_set_pixel(int argc, char **argv) {
     size_t x = strtoul(argv[1], NULL, 0);
     size_t y = strtoul(argv[2], NULL, 0);
     uint32_t color = strtoul(argv[3], NULL, 16);
     int invert = (argc == 5) && !strcmp(argv[4], "-i");
+    COVERAGE_ON();
     umka_sys_set_pixel(x, y, color, invert);
+    COVERAGE_OFF();
 }
 
-void umka_write_text(int argc, char **argv) {
+void shell_write_text(int argc, char **argv) {
     (void)argc;
     size_t x = strtoul(argv[1], NULL, 0);
     size_t y = strtoul(argv[2], NULL, 0);
@@ -302,10 +314,12 @@ void umka_write_text(int argc, char **argv) {
     int scale_factor = strtoul(argv[9], NULL, 0);
     int length = strtoul(argv[10], NULL, 0);
     int background_color_or_buffer = strtoul(argv[11], NULL, 0);
+    COVERAGE_ON();
     umka_sys_write_text(x, y, color, asciiz, fill_background, font_and_encoding, draw_to_buffer, scale_factor, string, length, background_color_or_buffer);
+    COVERAGE_OFF();
 }
 
-void umka_dump_win_stack(int argc, char **argv) {
+void shell_dump_win_stack(int argc, char **argv) {
     int depth = 5;
     if (argc > 1) {
         depth = strtol(argv[1], NULL, 0);
@@ -315,7 +329,7 @@ void umka_dump_win_stack(int argc, char **argv) {
     }
 }
 
-void umka_dump_win_pos(int argc, char **argv) {
+void shell_dump_win_pos(int argc, char **argv) {
     int depth = 5;
     if (argc > 1) {
         depth = strtol(argv[1], NULL, 0);
@@ -325,11 +339,13 @@ void umka_dump_win_pos(int argc, char **argv) {
     }
 }
 
-void umka_process_info(int argc, char **argv) {
+void shell_process_info(int argc, char **argv) {
     (void)argc;
     process_information_t info;
     int32_t pid = strtol(argv[1], NULL, 0);
+    COVERAGE_ON();
     umka_sys_process_info(pid, &info);
+    COVERAGE_OFF();
     printf("cpu_usage: %u\n", info.cpu_usage);
     printf("window_stack_position: %u\n", info.window_stack_position);
     printf("window_stack_value: %u\n", info.window_stack_value);
@@ -343,7 +359,7 @@ void umka_process_info(int argc, char **argv) {
     printf("wnd_state: 0x%.2" PRIx8 "\n", info.wnd_state);
 }
 
-void umka_display_number(int argc, char **argv) {
+void shell_display_number(int argc, char **argv) {
     (void)argc;
     int is_pointer = strtoul(argv[1], NULL, 0);
     int base = strtoul(argv[2], NULL, 0);
@@ -363,10 +379,12 @@ void umka_display_number(int argc, char **argv) {
     int draw_to_buffer = strtoul(argv[12], NULL, 0);
     int scale_factor = strtoul(argv[13], NULL, 0);
     uintptr_t background_color_or_buffer = strtoul(argv[14], NULL, 16);
+    COVERAGE_ON();
     umka_sys_display_number(is_pointer, base, digits_to_display, is_qword, show_leading_zeros, number_or_pointer, x, y, color, fill_background, font, draw_to_buffer, scale_factor, background_color_or_buffer);
+    COVERAGE_OFF();
 }
 
-void umka_set_window_colors(int argc, char **argv) {
+void shell_set_window_colors(int argc, char **argv) {
     if (argc != (1 + sizeof(system_colors_t)/4)) {
         printf("10 colors required\n");
         return;
@@ -382,14 +400,18 @@ void umka_set_window_colors(int argc, char **argv) {
     colors.work_button_text = strtoul(argv[8], NULL, 16);
     colors.work_text        = strtoul(argv[9], NULL, 16);
     colors.work_graph       = strtoul(argv[10], NULL, 16);
+    COVERAGE_ON();
     umka_sys_set_window_colors(&colors);
+    COVERAGE_OFF();
 }
 
-void umka_get_window_colors(int argc, char **argv) {
+void shell_get_window_colors(int argc, char **argv) {
     (void)argc;
     (void)argv;
     system_colors_t colors;
+    COVERAGE_ON();
     umka_sys_get_window_colors(&colors);
+    COVERAGE_OFF();
     printf("0x%.8" PRIx32 " frame\n", colors.frame);
     printf("0x%.8" PRIx32 " grab\n", colors.grab);
     printf("0x%.8" PRIx32 " work_3d_dark\n", colors.work_3d_dark);
@@ -402,25 +424,29 @@ void umka_get_window_colors(int argc, char **argv) {
     printf("0x%.8" PRIx32 " work_graph\n", colors.work_graph);
 }
 
-void umka_get_skin_height(int argc, char **argv) {
+void shell_get_skin_height(int argc, char **argv) {
     (void)argc;
     (void)argv;
+    COVERAGE_ON();
     uint32_t skin_height = umka_sys_get_skin_height();
+    COVERAGE_OFF();
     printf("%" PRIu32 "\n", skin_height);
 }
 
-void umka_get_screen_area(int argc, char **argv) {
+void shell_get_screen_area(int argc, char **argv) {
     (void)argc;
     (void)argv;
     rect_t wa;
+    COVERAGE_ON();
     umka_sys_get_screen_area(&wa);
+    COVERAGE_OFF();
     printf("%" PRIu32 " left\n", wa.left);
     printf("%" PRIu32 " top\n", wa.top);
     printf("%" PRIu32 " right\n", wa.right);
     printf("%" PRIu32 " bottom\n", wa.bottom);
 }
 
-void umka_set_screen_area(int argc, char **argv) {
+void shell_set_screen_area(int argc, char **argv) {
     if (argc != 5) {
         printf("left top right bottom\n");
         return;
@@ -430,61 +456,77 @@ void umka_set_screen_area(int argc, char **argv) {
     wa.top    = strtoul(argv[2], NULL, 0);
     wa.right  = strtoul(argv[3], NULL, 0);
     wa.bottom = strtoul(argv[4], NULL, 0);
+    COVERAGE_ON();
     umka_sys_set_screen_area(&wa);
+    COVERAGE_OFF();
 }
 
-void umka_get_skin_margins(int argc, char **argv) {
+void shell_get_skin_margins(int argc, char **argv) {
     (void)argc;
     (void)argv;
     rect_t wa;
+    COVERAGE_ON();
     umka_sys_get_skin_margins(&wa);
+    COVERAGE_OFF();
     printf("%" PRIu32 " left\n", wa.left);
     printf("%" PRIu32 " top\n", wa.top);
     printf("%" PRIu32 " right\n", wa.right);
     printf("%" PRIu32 " bottom\n", wa.bottom);
 }
 
-void umka_set_button_style(int argc, char **argv) {
+void shell_set_button_style(int argc, char **argv) {
     (void)argc;
     uint32_t style = strtoul(argv[1], NULL, 0);
+    COVERAGE_ON();
     umka_sys_set_button_style(style);
+    COVERAGE_OFF();
 }
 
-void umka_set_skin(int argc, char **argv) {
+void shell_set_skin(int argc, char **argv) {
     (void)argc;
     const char *path = argv[1];
+    COVERAGE_ON();
     int32_t status = umka_sys_set_skin(path);
+    COVERAGE_OFF();
     printf("status: %" PRIi32 "\n", status);
 }
 
-void umka_get_font_smoothing(int argc, char **argv) {
+void shell_get_font_smoothing(int argc, char **argv) {
     (void)argc;
     (void)argv;
     const char *names[] = {"off", "anti-aliasing", "subpixel"};
+    COVERAGE_ON();
     int type = umka_sys_get_font_smoothing();
+    COVERAGE_OFF();
     printf("font smoothing: %i - %s\n", type, names[type]);
 }
 
-void umka_set_font_smoothing(int argc, char **argv) {
+void shell_set_font_smoothing(int argc, char **argv) {
     (void)argc;
     int type = strtol(argv[1], NULL, 0);
+    COVERAGE_ON();
     umka_sys_set_font_smoothing(type);
+    COVERAGE_OFF();
 }
 
-void umka_get_font_size(int argc, char **argv) {
+void shell_get_font_size(int argc, char **argv) {
     (void)argc;
     (void)argv;
+    COVERAGE_ON();
     size_t size = umka_sys_get_font_size();
+    COVERAGE_OFF();
     printf("%upx\n", size);
 }
 
-void umka_set_font_size(int argc, char **argv) {
+void shell_set_font_size(int argc, char **argv) {
     (void)argc;
     uint32_t size = strtoul(argv[1], NULL, 0);
+    COVERAGE_ON();
     umka_sys_set_font_size(size);
+    COVERAGE_OFF();
 }
 
-void umka_button(int argc, char **argv) {
+void shell_button(int argc, char **argv) {
     (void)argc;
     size_t x     = strtoul(argv[1], NULL, 0);
     size_t xsize = strtoul(argv[2], NULL, 0);
@@ -494,10 +536,12 @@ void umka_button(int argc, char **argv) {
     uint32_t color = strtoul(argv[6], NULL, 16);
     int draw_button = strtoul(argv[7], NULL, 0);
     int draw_frame = strtoul(argv[8], NULL, 0);
+    COVERAGE_ON();
     umka_sys_button(x, xsize, y, ysize, button_id, draw_button, draw_frame, color);
+    COVERAGE_OFF();
 }
 
-void umka_put_image(int argc, char **argv) {
+void shell_put_image(int argc, char **argv) {
     (void)argc;
     FILE *f = fopen(argv[1], "r");
     fseek(f, 0, SEEK_END);
@@ -510,11 +554,13 @@ void umka_put_image(int argc, char **argv) {
     size_t ysize = strtoul(argv[3], NULL, 0);
     size_t x = strtoul(argv[4], NULL, 0);
     size_t y = strtoul(argv[5], NULL, 0);
+    COVERAGE_ON();
     umka_sys_put_image(image, xsize, ysize, x, y);
+    COVERAGE_OFF();
     free(image);
 }
 
-void umka_put_image_palette(int argc, char **argv) {
+void shell_put_image_palette(int argc, char **argv) {
     (void)argc;
     FILE *f = fopen(argv[1], "r");
     fseek(f, 0, SEEK_END);
@@ -530,47 +576,57 @@ void umka_put_image_palette(int argc, char **argv) {
     size_t bpp = strtoul(argv[6], NULL, 0);
     void *palette = NULL;
     size_t row_offset = strtoul(argv[7], NULL, 0);
+    COVERAGE_ON();
     umka_sys_put_image_palette(image, xsize, ysize, x, y, bpp, palette, row_offset);
+    COVERAGE_OFF();
     free(image);
 }
 
-void umka_draw_rect(int argc, char **argv) {
+void shell_draw_rect(int argc, char **argv) {
     size_t x     = strtoul(argv[1], NULL, 0);
     size_t xsize = strtoul(argv[2], NULL, 0);
     size_t y     = strtoul(argv[3], NULL, 0);
     size_t ysize = strtoul(argv[4], NULL, 0);
     uint32_t color = strtoul(argv[5], NULL, 16);
     int gradient = (argc == 7) && !strcmp(argv[6], "-g");
+    COVERAGE_ON();
     umka_sys_draw_rect(x, xsize, y, ysize, color, gradient);
+    COVERAGE_OFF();
 }
 
-void umka_get_screen_size(int argc, char **argv) {
+void shell_get_screen_size(int argc, char **argv) {
     (void)argc;
     (void)argv;
     uint32_t xsize, ysize;
+    COVERAGE_ON();
     umka_sys_get_screen_size(&xsize, &ysize);
+    COVERAGE_OFF();
     printf("%" PRIu32 "x%" PRIu32 "\n", xsize, ysize);
 }
 
-void umka_draw_line(int argc, char **argv) {
+void shell_draw_line(int argc, char **argv) {
     size_t x    = strtoul(argv[1], NULL, 0);
     size_t xend = strtoul(argv[2], NULL, 0);
     size_t y    = strtoul(argv[3], NULL, 0);
     size_t yend = strtoul(argv[4], NULL, 0);
     uint32_t color = strtoul(argv[5], NULL, 16);
     int invert = (argc == 7) && !strcmp(argv[6], "-i");
+    COVERAGE_ON();
     umka_sys_draw_line(x, xend, y, yend, color, invert);
+    COVERAGE_OFF();
 }
 
-void umka_set_window_caption(int argc, char **argv) {
+void shell_set_window_caption(int argc, char **argv) {
     (void)argc;
     const char *caption = argv[1];
     int encoding = strtoul(argv[2], NULL, 0);
+    COVERAGE_ON();
     umka_sys_set_window_caption(caption, encoding);
+    COVERAGE_OFF();
 }
 
 
-void umka_draw_window(int argc, char **argv) {
+void shell_draw_window(int argc, char **argv) {
     (void)argc;
     size_t x     = strtoul(argv[1], NULL, 0);
     size_t xsize = strtoul(argv[2], NULL, 0);
@@ -584,25 +640,31 @@ void umka_draw_window(int argc, char **argv) {
     int movable = strtoul(argv[10], NULL, 0);
     int style = strtoul(argv[11], NULL, 0);
     const char *caption = argv[12];
+    COVERAGE_ON();
     umka_sys_draw_window(x, xsize, y, ysize, color, has_caption, client_relative, fill_workarea, gradient_fill, movable, style, caption);
+    COVERAGE_OFF();
 }
 
-void umka_window_redraw(int argc, char **argv) {
+void shell_window_redraw(int argc, char **argv) {
     (void)argc;
     int begin_end = strtoul(argv[1], NULL, 0);
+    COVERAGE_ON();
     umka_sys_window_redraw(begin_end);
+    COVERAGE_OFF();
 }
 
-void umka_move_window(int argc, char **argv) {
+void shell_move_window(int argc, char **argv) {
     (void)argc;
     size_t x      = strtoul(argv[1], NULL, 0);
     size_t y      = strtoul(argv[2], NULL, 0);
     ssize_t xsize = strtol(argv[3], NULL, 0);
     ssize_t ysize = strtol(argv[4], NULL, 0);
+    COVERAGE_ON();
     umka_sys_move_window(x, y, xsize, ysize);
+    COVERAGE_OFF();
 }
 
-void umka_blit_bitmap(int argc, char **argv) {
+void shell_blit_bitmap(int argc, char **argv) {
     (void)argc;
     FILE *f = fopen(argv[1], "r");
     fseek(f, 0, SEEK_END);
@@ -625,14 +687,18 @@ void umka_blit_bitmap(int argc, char **argv) {
     int client_relative = strtoul(argv[13], NULL, 0);
     int row_length = strtoul(argv[14], NULL, 0);
     uint32_t params[] = {dstx, dsty, dstxsize, dstysize, srcx, srcy, srcxsize, srcysize, (uintptr_t)image, row_length};
+    COVERAGE_ON();
     umka_sys_blit_bitmap(operation, background, transparent, client_relative, params);
+    COVERAGE_OFF();
     free(image);
 }
 
-void umka_scrot(int argc, char **argv) {
+void shell_scrot(int argc, char **argv) {
     (void)argc;
     uint32_t xsize, ysize;
+    COVERAGE_ON();
     umka_sys_get_screen_size(&xsize, &ysize);
+    COVERAGE_OFF();
 
     uint32_t *lfb = kos_lfb_base;
     for (size_t y = 0; y < ysize; y++) {
@@ -647,7 +713,9 @@ void umka_scrot(int argc, char **argv) {
 
 void shell_cd(int argc, char **argv) {
     (void)argc;
+    COVERAGE_ON();
     umka_sys_set_cwd(argv[1]);
+    COVERAGE_OFF();
     cur_dir_changed = true;
 }
 
@@ -662,7 +730,9 @@ void ls_range(f7080s1arg_t *fX0, f70or80_t f70or80) {
         if (fX0->size > requested) {
             fX0->size = requested;
         }
+        COVERAGE_ON();
         umka_sys_lfn(fX0, &r, f70or80);
+        COVERAGE_OFF();
         fX0->offset += fX0->size;
         print_f70_status(&r, 1);
         f7080s1info_t *dir = fX0->buf;
@@ -690,7 +760,9 @@ void ls_all(f7080s1arg_t *fX0, f70or80_t f70or80) {
     f7080ret_t r;
     size_t bdfe_len = (fX0->encoding == CP866) ? BDFE_LEN_CP866 : BDFE_LEN_UNICODE;
     while (true) {
+        COVERAGE_ON();
         umka_sys_lfn(fX0, &r, f70or80);
+        COVERAGE_OFF();
         print_f70_status(&r, 1);
         assert((r.status == ERROR_SUCCESS && r.count == fX0->size)
               || (r.status == ERROR_END_OF_FILE && r.count < fX0->size));
@@ -733,7 +805,7 @@ fs_enc_t parse_encoding(const char *str) {
     return enc;
 }
 
-void umka_ls(int argc, char **argv, const char *usage, f70or80_t f70or80) {
+void shell_ls(int argc, char **argv, const char *usage, f70or80_t f70or80) {
     int opt;
     optind = 1;
     const char *optstring = (f70or80 == F70) ? "f:c:e:" : "f:c:e:p:";
@@ -783,17 +855,17 @@ void umka_ls(int argc, char **argv, const char *usage, f70or80_t f70or80) {
     return;
 }
 
-void umka_ls70(int argc, char **argv) {
+void shell_ls70(int argc, char **argv) {
     const char *usage = \
         "usage: ls70 [dir] [option]...\n"
         "  -f number        index of the first dir entry to read\n"
         "  -c number        number of dir entries to read\n"
         "  -e encoding      cp866|utf16|utf8\n"
         "                   return directory listing in this encoding";
-    umka_ls(argc, argv, usage, F70);
+    shell_ls(argc, argv, usage, F70);
 }
 
-void umka_ls80(int argc, char **argv) {
+void shell_ls80(int argc, char **argv) {
     const char *usage = \
         "usage: ls80 [dir] [option]...\n"
         "  -f number        index of the first dir entry to read\n"
@@ -802,10 +874,10 @@ void umka_ls80(int argc, char **argv) {
         "                   return directory listing in this encoding\n"
         "  -p encoding      cp866|utf16|utf8\n"
         "                   path to dir is specified in this encoding";
-    umka_ls(argc, argv, usage, F80);
+    shell_ls(argc, argv, usage, F80);
 }
 
-void umka_stat(int argc, char **argv, f70or80_t f70or80) {
+void shell_stat(int argc, char **argv, f70or80_t f70or80) {
     (void)argc;
     f7080s5arg_t fX0 = {.sf = 5, .flags = 0};
     f7080ret_t r;
@@ -818,7 +890,9 @@ void umka_stat(int argc, char **argv, f70or80_t f70or80) {
         fX0.u.f80.path_encoding = DEFAULT_PATH_ENCODING;
         fX0.u.f80.path = argv[1];
     }
+    COVERAGE_ON();
     umka_sys_lfn(&fX0, &r, f70or80);
+    COVERAGE_OFF();
     print_f70_status(&r, 0);
     if (r.status != ERROR_SUCCESS)
         return;
@@ -851,15 +925,15 @@ void umka_stat(int argc, char **argv, f70or80_t f70or80) {
     return;
 }
 
-void umka_stat70(int argc, char **argv) {
-    umka_stat(argc, argv, F70);
+void shell_stat70(int argc, char **argv) {
+    shell_stat(argc, argv, F70);
 }
 
-void umka_stat80(int argc, char **argv) {
-    umka_stat(argc, argv, F80);
+void shell_stat80(int argc, char **argv) {
+    shell_stat(argc, argv, F80);
 }
 
-void umka_read(int argc, char **argv, f70or80_t f70or80) {
+void shell_read(int argc, char **argv, f70or80_t f70or80) {
     (void)argc;
     f7080s0arg_t fX0 = {.sf = 0};
     f7080ret_t r;
@@ -897,7 +971,9 @@ void umka_read(int argc, char **argv, f70or80_t f70or80) {
     }
     fX0.buf = (uint8_t*)malloc(fX0.count);
 
+    COVERAGE_ON();
     umka_sys_lfn(&fX0, &r, f70or80);
+    COVERAGE_OFF();
 
     print_f70_status(&r, 1);
     if (r.status == ERROR_SUCCESS || r.status == ERROR_END_OF_FILE) {
@@ -911,12 +987,12 @@ void umka_read(int argc, char **argv, f70or80_t f70or80) {
     return;
 }
 
-void umka_read70(int argc, char **argv) {
-    umka_read(argc, argv, F70);
+void shell_read70(int argc, char **argv) {
+    shell_read(argc, argv, F70);
 }
 
-void umka_read80(int argc, char **argv) {
-    umka_read(argc, argv, F80);
+void shell_read80(int argc, char **argv) {
+    shell_read(argc, argv, F80);
 }
 
 typedef struct {
@@ -925,47 +1001,47 @@ typedef struct {
 } func_table_t;
 
 func_table_t funcs[] = {
-                        { "disk_add",           umka_disk_add },
-                        { "disk_del",           umka_disk_del },
-                        { "ls70",               umka_ls70 },
-                        { "ls80",               umka_ls80 },
-                        { "stat70",             umka_stat70 },
-                        { "stat80",             umka_stat80 },
-                        { "read70",             umka_read70 },
-                        { "read80",             umka_read80 },
+                        { "disk_add",           shell_disk_add },
+                        { "disk_del",           shell_disk_del },
+                        { "ls70",               shell_ls70 },
+                        { "ls80",               shell_ls80 },
+                        { "stat70",             shell_stat70 },
+                        { "stat80",             shell_stat80 },
+                        { "read70",             shell_read70 },
+                        { "read80",             shell_read80 },
                         { "pwd",                shell_pwd },
                         { "cd",                 shell_cd },
                         { "set_cwd",            shell_cd },
-                        { "draw_window",        umka_draw_window },
-                        { "set_pixel",          umka_set_pixel },
-                        { "write_text",         umka_write_text },
-                        { "put_image",          umka_put_image },
-                        { "button",             umka_button },
-                        { "process_info",       umka_process_info },
-                        { "window_redraw",      umka_window_redraw },
-                        { "draw_rect",          umka_draw_rect },
-                        { "get_screen_size",    umka_get_screen_size },
-                        { "draw_line",          umka_draw_line },
-                        { "display_number",     umka_display_number },
-                        { "set_button_style",   umka_set_button_style },
-                        { "set_window_colors",  umka_set_window_colors },
-                        { "get_window_colors",  umka_get_window_colors },
-                        { "get_skin_height",    umka_get_skin_height },
-                        { "get_screen_area",    umka_get_screen_area },
-                        { "set_screen_area",    umka_set_screen_area },
-                        { "get_skin_margins",   umka_get_skin_margins },
-                        { "set_skin",           umka_set_skin },
-                        { "get_font_smoothing", umka_get_font_smoothing },
-                        { "set_font_smoothing", umka_set_font_smoothing },
-                        { "get_font_size",      umka_get_font_size },
-                        { "set_font_size",      umka_set_font_size },
-                        { "put_image_palette",  umka_put_image_palette },
-                        { "move_window",        umka_move_window },
-                        { "set_window_caption", umka_set_window_caption },
-                        { "blit_bitmap",        umka_blit_bitmap },
-                        { "scrot",              umka_scrot },
-                        { "dump_win_stack",     umka_dump_win_stack },
-                        { "dump_win_pos",       umka_dump_win_pos },
+                        { "draw_window",        shell_draw_window },
+                        { "set_pixel",          shell_set_pixel },
+                        { "write_text",         shell_write_text },
+                        { "put_image",          shell_put_image },
+                        { "button",             shell_button },
+                        { "process_info",       shell_process_info },
+                        { "window_redraw",      shell_window_redraw },
+                        { "draw_rect",          shell_draw_rect },
+                        { "get_screen_size",    shell_get_screen_size },
+                        { "draw_line",          shell_draw_line },
+                        { "display_number",     shell_display_number },
+                        { "set_button_style",   shell_set_button_style },
+                        { "set_window_colors",  shell_set_window_colors },
+                        { "get_window_colors",  shell_get_window_colors },
+                        { "get_skin_height",    shell_get_skin_height },
+                        { "get_screen_area",    shell_get_screen_area },
+                        { "set_screen_area",    shell_set_screen_area },
+                        { "get_skin_margins",   shell_get_skin_margins },
+                        { "set_skin",           shell_set_skin },
+                        { "get_font_smoothing", shell_get_font_smoothing },
+                        { "set_font_smoothing", shell_set_font_smoothing },
+                        { "get_font_size",      shell_get_font_size },
+                        { "set_font_size",      shell_set_font_size },
+                        { "put_image_palette",  shell_put_image_palette },
+                        { "move_window",        shell_move_window },
+                        { "set_window_caption", shell_set_window_caption },
+                        { "blit_bitmap",        shell_blit_bitmap },
+                        { "scrot",              shell_scrot },
+                        { "dump_win_stack",     shell_dump_win_stack },
+                        { "dump_win_pos",       shell_dump_win_pos },
                         { NULL,                 NULL },
                        };
 
@@ -977,7 +1053,7 @@ void *run_test(const char *infile_name) {
         outfile = stdout;
     } else {
         char outfile_name[PATH_MAX];
-        strncpy(outfile_name, infile_name, PATH_MAX-2);    // ".t" is shorter that ".out"
+        strncpy(outfile_name, infile_name, PATH_MAX-2);    // ".t" is shorter than ".out"
         char *last_dot = strrchr(outfile_name, '.');
         if (!last_dot) {
             printf("test file must have '.t' suffix\n");
@@ -993,7 +1069,7 @@ void *run_test(const char *infile_name) {
     }
 
     int is_tty = isatty(fileno(infile));
-    char **cargv = (char**)malloc(sizeof(char*) * (MAX_COMMAND_ARGS + 1));
+    char **argv = (char**)malloc(sizeof(char*) * (MAX_COMMAND_ARGS + 1));
     while(next_line(infile, is_tty)) {
         if (cmd_buf[0] == '#' || cmd_buf[0] == '\n') {
             printf("%s", cmd_buf);
@@ -1005,20 +1081,20 @@ void *run_test(const char *infile_name) {
             printf("%s", cmd_buf);
             fflush(outfile);
         }
-        int cargc = split_args(cmd_buf, cargv);
+        int argc = split_args(cmd_buf, argv);
         func_table_t *ft;
         for (ft = funcs; ft->name != NULL; ft++) {
-            if (!strcmp(cargv[0], ft->name)) {
+            if (!strcmp(argv[0], ft->name)) {
                 break;
             }
         }
         if (ft->name) {
-            ft->func(cargc, cargv);
+            ft->func(argc, argv);
         } else {
-            printf("unknown command: %s\n", cargv[0]);
+            printf("unknown command: %s\n", argv[0]);
         }
     }
-    free(cargv);
+    free(argv);
 
     return NULL;
 }
@@ -1026,7 +1102,7 @@ void *run_test(const char *infile_name) {
 int main(int argc, char **argv) {
     const char *usage = \
         "usage: umka_shell [test_file.t] [-c]\n"
-        "  -c               trace branches to collect coverage";
+        "  -c               collect coverage";
     const char *test_file = NULL;
 
     int opt;
@@ -1037,7 +1113,7 @@ int main(int argc, char **argv) {
     while ((opt = getopt(argc, argv, "c")) != -1) {
         switch (opt) {
         case 'c':
-            trace = 1;
+            coverage = 1;
             break;
         default:
             puts(usage);
@@ -1045,13 +1121,16 @@ int main(int argc, char **argv) {
         }
     }
 
-    if (trace)
+    if (coverage)
         trace_begin();
+
+    COVERAGE_ON();
     kos_init();
+    COVERAGE_OFF();
 
     run_test(test_file);
 
-    if (trace)
+    if (coverage)
         trace_end();
 
     return 0;