d0f7acf9eb
An x86-64 operating system built from xv6, now largely rewritten: SMP, a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF rasteriser, and a Linux-numbered syscall ABI. No history before this point -- the tree was never under version control. This commit exists so the rename that follows has something to undo to.
555 lines
18 KiB
C
555 lines
18 KiB
C
#include "types.h"
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#include "x86.h"
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#include "memlayout.h"
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#include "defs.h"
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#include "theme.h"
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#include "font.h"
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#include "logo.h"
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#include "device.h"
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#include "display.h"
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#include "dma.h"
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#define BACKSPACE 0x100
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#define CHAR_HEIGHT 16
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#define CHAR_WIDTH 8
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#define COLOR_BG SCH_BG
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volatile uchar *vga_mem = 0;
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// Physical base of the linear framebuffer, as reported by VBE. Every other
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// part of the kernel that needs to map the framebuffer -- fork's VMA copy,
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// mmap of /dev/fb0 -- asks for this rather than assuming a value. Three
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// places used to hardcode 0xfd000000, which is only where QEMU's stdvga
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// happens to put it.
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static uint64 vga_phys = 0;
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static uint32 vga_stride = 0;
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static uint32 vga_bpp = 0;
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static uint32 vga_width = 800;
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static uint32 vga_height = 600;
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static int cursor_x = 0;
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static int cursor_y = 0;
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// Current fill color for glyph backgrounds, backspace erase, and scroll —
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// normally COLOR_BG, but panic() switches this to paint the whole console
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// a solid color (e.g. PSOGM's purple) instead of leaving cream-colored boxes
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// around each character.
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static uint32 vga_bg = COLOR_BG;
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void
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vga_set_bg(uint32 color)
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{
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vga_bg = color;
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}
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// Written by boot/stage2.S's VBE call and read by boot/stage2main.c under
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// the same name (VBE_INFO_ADDR) — not 0x9000, since stage2's own code now
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// runs up to nearly 0x9000 once the boot-menu/progress-bar logic is
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// included, which would otherwise clobber a mode info block placed there.
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#define VBE_INFO_ADDR 0x30000
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void
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vga_init(uint64 phys_addr) {
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if (phys_addr == 0) {
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phys_addr = *(uint32*)(P2V(VBE_INFO_ADDR) + 40);
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}
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vga_mem = (volatile uchar*)P2V(phys_addr);
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vga_phys = phys_addr;
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vga_stride = *(ushort*)(P2V(VBE_INFO_ADDR) + 16);
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vga_width = *(ushort*)(P2V(VBE_INFO_ADDR) + 18);
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vga_height = *(ushort*)(P2V(VBE_INFO_ADDR) + 20);
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vga_bpp = *(uchar*)(P2V(VBE_INFO_ADDR) + 25);
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if (vga_width == 0) vga_width = 800;
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if (vga_height == 0) vga_height = 600;
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if (vga_stride == 0) vga_stride = vga_width * (vga_bpp / 8);
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cprintf("VGA: %dx%d, %d bpp, stride %d, LFB: 0x%x\n", vga_width, vga_height, vga_bpp, vga_stride, (uint32)phys_addr);
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// Deliberately does NOT clear the screen.
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//
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// The bootloader has already drawn the splash, and wiping it here is what
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// produced the old two-act boot: a purple splash for an instant, then an
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// abrupt cream screen filling with kernel log lines. The splash now stays up
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// for the whole of boot, and console_takeover() clears it exactly once --
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// when userspace starts and the display changes owner.
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}
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void
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vga_draw_pixel(int x, int y, uint32 color)
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{
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if (!vga_mem || x < 0 || x >= vga_width || y < 0 || y >= vga_height)
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return;
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uint32 offset = (y * vga_stride) + (x * (vga_bpp / 8));
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if (vga_bpp == 32) {
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*(volatile uint32*)(vga_mem + offset) = color;
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} else if (vga_bpp == 24) {
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vga_mem[offset] = color & 0xFF;
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vga_mem[offset + 1] = (color >> 8) & 0xFF;
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vga_mem[offset + 2] = (color >> 16) & 0xFF;
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} else if (vga_bpp == 16) {
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uint16 c16 = (((color >> 19) & 0x1F) << 11) | (((color >> 10) & 0x3F) << 5) | ((color >> 3) & 0x1F);
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*(volatile uint16*)(vga_mem + offset) = c16;
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}
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}
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void
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vga_clear(uint32 color)
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{
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for (int y = 0; y < vga_height; y++) {
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for (int x = 0; x < vga_width; x++) {
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vga_draw_pixel(x, y, color);
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}
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}
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}
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void
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vga_draw_char(int x, int y, uchar c, uint32 color)
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{
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// No `c > 127` rejection any more: font_data holds 256 Latin-1 glyphs, and
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// a uchar cannot index past them.
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if (!vga_mem) return;
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for (int row = 0; row < CHAR_HEIGHT; row++) {
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uchar row_data = font_data[c][row];
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for (int col = 0; col < CHAR_WIDTH; col++) {
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if (row_data & (0x80 >> col)) {
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vga_draw_pixel(x + col, y + row, color);
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} else {
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vga_draw_pixel(x + col, y + row, vga_bg);
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}
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}
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}
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}
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void
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vga_puts(int x, int y, char *s, uint32 color)
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{
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while (*s) {
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vga_putc((uchar)*s, color);
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s++;
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}
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}
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void
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vga_putc(int c, uint32 color)
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{
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if (!vga_mem) return;
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if (c == BACKSPACE || c == 0x08 || c == '\b' || c == 127) {
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if (cursor_x >= CHAR_WIDTH) {
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cursor_x -= CHAR_WIDTH;
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for (int i = 0; i < CHAR_HEIGHT; i++) {
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for (int j = 0; j < CHAR_WIDTH; j++) {
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vga_draw_pixel(cursor_x + j, cursor_y + i, vga_bg);
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}
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}
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}
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return;
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}
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if (c == '\n') {
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cursor_x = 0;
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cursor_y += CHAR_HEIGHT;
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} else if (c == '\r') {
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cursor_x = 0;
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} else if (c == '\t') {
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// Advance to the next multiple of eight columns, erasing as it goes so a
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// tab overwrites rather than skipping over stale characters.
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//
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// There was no tab case at all, so '\t' fell through to vga_draw_char and
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// was drawn as glyph 9 -- which in CP437 is a hollow circle. Pressing Tab
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// printed a circle. Same for every other control character: the font has
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// a picture for each of them, and none of those pictures is what the
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// character means.
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int col = cursor_x / CHAR_WIDTH;
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int stop = (col + 8) & ~7;
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while (col < stop && cursor_x < (int)vga_width) {
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for (int i = 0; i < CHAR_HEIGHT; i++)
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for (int j = 0; j < CHAR_WIDTH; j++)
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vga_draw_pixel(cursor_x + j, cursor_y + i, vga_bg);
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cursor_x += CHAR_WIDTH;
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col++;
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}
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} else if (c < 32) {
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return; // any other control character: not a glyph
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} else {
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vga_draw_char(cursor_x, cursor_y, (uchar)c, color);
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cursor_x += CHAR_WIDTH;
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}
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if (cursor_x >= vga_width) {
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cursor_x = 0;
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cursor_y += CHAR_HEIGHT;
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}
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if (cursor_y > (vga_height - CHAR_HEIGHT)) {
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uint32 line_size = vga_stride * CHAR_HEIGHT;
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uint32 total_size = vga_stride * vga_height;
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uint32 copy_size = total_size - line_size;
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memmove((void*)vga_mem, (void*)(vga_mem + line_size), copy_size);
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for (int y = vga_height - CHAR_HEIGHT; y < vga_height; y++) {
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for (int x = 0; x < vga_width; x++) {
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vga_draw_pixel(x, y, vga_bg);
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}
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}
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cursor_y = vga_height - CHAR_HEIGHT;
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}
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}
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void
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vga_screen_reset(void)
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{
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vga_bg = COLOR_BG;
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vga_clear(COLOR_BG);
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cursor_x = 0;
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cursor_y = 0;
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}
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/* ------------------------------------------------------------------ */
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/* Drawing primitives for the crash screen */
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/* */
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/* The crash screen lays itself out rather than printing, which needs */
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/* two things the console never did: filled shapes, and text at an */
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/* absolute position that leaves the cursor alone. */
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/* ------------------------------------------------------------------ */
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int
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vga_ready(void)
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{
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return vga_mem != 0;
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}
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void
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vga_dims(int *w, int *h)
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{
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if (w) *w = (int)vga_width;
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if (h) *h = (int)vga_height;
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}
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int vga_char_w(void) { return CHAR_WIDTH; }
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int vga_char_h(void) { return CHAR_HEIGHT; }
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/* ------------------------------------------------------------------ */
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/* Framebuffer geometry */
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/* */
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/* vga.c is the only place that reads the VBE mode info, so it is the */
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/* only place that knows where the framebuffer actually is. Everything */
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/* else asks. See kernel/dev/fb.c for the device these back. */
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/* ------------------------------------------------------------------ */
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uint64 vga_fb_phys(void) { return vga_phys; }
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// Bytes of framebuffer, measured in scanlines rather than as
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// width * height * bpp/8 -- the two differ whenever the card pads its rows,
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// and it is the stride that says how far apart two rows really are.
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uint64 vga_fb_size(void)
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{
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if (!vga_mem)
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return 0;
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return (uint64)vga_stride * (uint64)vga_height;
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}
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uint32 vga_fb_stride(void) { return vga_stride; }
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uint32 vga_fb_bpp(void) { return vga_bpp; }
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volatile uchar *vga_fb_ptr(void) { return vga_mem; }
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/* ------------------------------------------------------------------ */
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/* Cursor addressing and erasing */
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/* */
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/* What an ANSI escape parser needs and vga_putc alone cannot give it: */
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/* the ability to put the cursor somewhere specific and to erase a */
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/* region without writing spaces over it. See kernel/core/console.c. */
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/* ------------------------------------------------------------------ */
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int vga_cols(void) { return vga_width ? (int)(vga_width / CHAR_WIDTH) : 0; }
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int vga_rows(void) { return vga_height ? (int)(vga_height / CHAR_HEIGHT) : 0; }
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void
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vga_cursor_get(int *col, int *row)
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{
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if (col) *col = cursor_x / CHAR_WIDTH;
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if (row) *row = cursor_y / CHAR_HEIGHT;
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}
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// Clamped rather than validated: an escape sequence is untrusted input that
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// arrives from any program that can write to the terminal, and "CUP to row
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// 9999" should put the cursor on the last row, not off the end of the
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// framebuffer.
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void
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vga_cursor_set(int col, int row)
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{
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int maxc = vga_cols(), maxr = vga_rows();
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if (maxc <= 0 || maxr <= 0)
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return;
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if (col < 0) col = 0;
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if (row < 0) row = 0;
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if (col >= maxc) col = maxc - 1;
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if (row >= maxr) row = maxr - 1;
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cursor_x = col * CHAR_WIDTH;
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cursor_y = row * CHAR_HEIGHT;
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}
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// Fill a run of character cells with the background colour.
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static void
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erase_cells(int col, int row, int count)
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{
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int maxc = vga_cols();
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while (count-- > 0) {
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int x = col * CHAR_WIDTH, y = row * CHAR_HEIGHT;
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for (int i = 0; i < CHAR_HEIGHT; i++)
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for (int j = 0; j < CHAR_WIDTH; j++)
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vga_draw_pixel(x + j, y + i, vga_bg);
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if (++col >= maxc) { col = 0; row++; }
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}
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}
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// ED -- erase in display. 0: cursor to end, 1: start to cursor, 2: all.
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void
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vga_erase_display(int mode)
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{
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int col, row, maxc = vga_cols(), maxr = vga_rows();
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vga_cursor_get(&col, &row);
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switch (mode) {
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case 0: erase_cells(col, row, (maxr - row) * maxc - col); break;
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case 1: erase_cells(0, 0, row * maxc + col + 1); break;
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default: vga_clear(vga_bg); break;
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}
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}
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// EL -- erase in line. Same three modes, bounded to the current row.
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void
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vga_erase_line(int mode)
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{
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int col, row, maxc = vga_cols();
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vga_cursor_get(&col, &row);
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switch (mode) {
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case 0: erase_cells(col, row, maxc - col); break;
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case 1: erase_cells(0, row, col + 1); break;
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default: erase_cells(0, row, maxc); break;
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}
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}
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// Row pointer computed once per row rather than per pixel. The crash screen
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// paints a solid card behind the QR symbol, and at 8 pixels per module that is
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// tens of thousands of writes going through vga_draw_pixel's bounds check and
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// multiply.
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void
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vga_fill_rect(int x0, int y0, int w, int h, uint32 color)
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{
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if (!vga_mem)
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return;
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if (x0 < 0) { w += x0; x0 = 0; }
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if (y0 < 0) { h += y0; y0 = 0; }
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if (x0 + w > (int)vga_width) w = (int)vga_width - x0;
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if (y0 + h > (int)vga_height) h = (int)vga_height - y0;
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if (w <= 0 || h <= 0)
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return;
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// Only the 32bpp case gets the fast path; anything else is rare enough that
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// correctness through vga_draw_pixel is the better trade.
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if (vga_bpp != 32) {
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for (int y = y0; y < y0 + h; y++)
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for (int x = x0; x < x0 + w; x++)
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vga_draw_pixel(x, y, color);
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return;
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}
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for (int y = y0; y < y0 + h; y++) {
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volatile uint32 *row = (volatile uint32 *)(vga_mem + y * vga_stride) + x0;
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for (int x = 0; x < w; x++)
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row[x] = color;
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}
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}
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void
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vga_fill_circle(int cx, int cy, int r, uint32 color)
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{
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for (int dy = -r; dy <= r; dy++)
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for (int dx = -r; dx <= r; dx++)
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if (dx * dx + dy * dy <= r * r)
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vga_draw_pixel(cx + dx, cy + dy, color);
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}
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// Text at an absolute position, leaving the console cursor alone. The crash
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// screen lays itself out, so vga_putc's cursor tracking and scrolling are
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// exactly what it does not want.
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void
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vga_text_at(int x, int y, const char *s, uint32 color)
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{
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for (int i = 0; s[i]; i++)
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vga_draw_char(x + i * CHAR_WIDTH, y, (uchar)s[i], color);
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}
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// --- Logo ------------------------------------------------------------------
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//
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// The boot splash's logo is drawn by the *loader*, not here -- see splash() in
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// boot/stage2main.c. It has to be, because the kernel does not reach vga_init()
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// until roughly the last 300ms of a 2.8s boot: drawing it here put the logo on
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// screen for one frame before console_takeover() wiped it, which is worse than
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// not having one.
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//
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// What lives here is the same drawing code against the same mask, for the
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// things that want the mark *after* boot -- the crash screen, and eventually
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// whatever schinit shows. Keeping one copy of the compositing logic is why this
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// is not simply deleted.
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// Blend `fg` over `bg` by coverage a (0..255). Per-channel, integer only: this
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// runs before any floating point is safe to touch.
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static uint32
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blend(uint32 bg, uint32 fg, uint a)
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{
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uint32 r = (((fg >> 16) & 0xFF) * a + ((bg >> 16) & 0xFF) * (255 - a)) / 255;
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uint32 g = (((fg >> 8) & 0xFF) * a + ((bg >> 8) & 0xFF) * (255 - a)) / 255;
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uint32 b = (((fg ) & 0xFF) * a + ((bg ) & 0xFF) * (255 - a)) / 255;
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return (r << 16) | (g << 8) | b;
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}
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void
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vga_draw_logo(int x, int y, uint32 color, uint32 bg)
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{
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if (!vga_mem)
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return;
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for (int dy = 0; dy < LOGO_H; dy++) {
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for (int dx = 0; dx < LOGO_W; dx++) {
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uint a = LOGO_INK(dy * LOGO_W + dx);
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// Skip the background rather than painting it. The mask is a square but
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// the mark is a circle, so most of it is empty -- and drawing that empty
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// area in bg would stamp a visible box over whatever is underneath.
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if (a == 0)
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continue;
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vga_draw_pixel(x + dx, y + dy, a == 255 ? color : blend(bg, color, a));
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}
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}
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}
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// Centred, for callers that own the whole screen.
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void
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vga_logo_centered(int cy, uint32 color, uint32 bg)
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{
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if (!vga_mem || vga_width < LOGO_W)
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return;
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vga_draw_logo(((int)vga_width - LOGO_W) / 2, cy - LOGO_H / 2, color, bg);
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}
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// --- display class implementation ------------------------------------------
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//
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// See include/display.h. This is the VBE linear framebuffer presenting itself
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// as a generic display, so a compositor can be written against the class and
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// keep working when virtio-gpu arrives.
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static uchar *back; // shadow buffer in RAM, or 0 if never acquired
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static uint64 back_bytes;
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static void
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vga_disp_mode(struct device *d, struct display_mode *m)
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{
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m->width = (int)vga_width;
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m->height = (int)vga_height;
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m->bpp = (int)vga_bpp;
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m->stride = vga_stride;
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}
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static void *
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vga_disp_acquire(struct device *d, uint32 *stride_out)
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{
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if (stride_out)
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*stride_out = vga_stride;
|
|
if (back)
|
|
return back;
|
|
if (!vga_mem || vga_height == 0 || vga_stride == 0)
|
|
return 0;
|
|
|
|
back_bytes = (uint64)vga_stride * vga_height;
|
|
|
|
// From the DMA arena, which is the wrong pool and is used here because it is
|
|
// the only *physically contiguous* allocator in the kernel -- kalloc hands
|
|
// out single pages whose neighbours are adjacent only by chance, and a
|
|
// framebuffer wants one flat span.
|
|
//
|
|
// At 800x600x32 this is 1.9 MB of a 4 MB arena meant for device rings, which
|
|
// is tolerable only because nothing else large lives there yet. The real fix
|
|
// is a contiguous page allocator, or reserving this at boot from the memory
|
|
// map -- which is work that belongs with the E820 change in docs/roadmap.md
|
|
// §3b, since that is what stops the kernel pretending 224 MB exists.
|
|
//
|
|
// Allocated on first use rather than at boot on purpose: a machine that never
|
|
// starts a compositor should not pay two megabytes for one.
|
|
back = dma_alloc(back_bytes, 4096);
|
|
if (!back) {
|
|
cprintf("display: no room for a %d KB back buffer; drawing will tear\n",
|
|
(int)(back_bytes / 1024));
|
|
return 0;
|
|
}
|
|
memset(back, 0, back_bytes);
|
|
cprintf("display: %d KB back buffer, double buffered\n",
|
|
(int)(back_bytes / 1024));
|
|
return back;
|
|
}
|
|
|
|
// Blit a rectangle from the shadow buffer to the framebuffer.
|
|
//
|
|
// Row at a time rather than one memmove for the whole rectangle: only a
|
|
// full-width rectangle is contiguous in either buffer, and a compositor
|
|
// updating one window is the case worth being right about.
|
|
static void
|
|
vga_disp_present(struct device *d, int x, int y, int w, int h)
|
|
{
|
|
if (!back || !vga_mem)
|
|
return;
|
|
|
|
if (x < 0) { w += x; x = 0; }
|
|
if (y < 0) { h += y; y = 0; }
|
|
if (x + w > (int)vga_width) w = (int)vga_width - x;
|
|
if (y + h > (int)vga_height) h = (int)vga_height - y;
|
|
if (w <= 0 || h <= 0)
|
|
return;
|
|
|
|
int bytes = w * (int)(vga_bpp / 8);
|
|
uint32 off = (uint32)x * (vga_bpp / 8);
|
|
for (int row = y; row < y + h; row++)
|
|
memmove((void *)(vga_mem + row * vga_stride + off),
|
|
back + row * vga_stride + off, bytes);
|
|
}
|
|
|
|
// Wait for vertical retrace, by polling the VGA input status register.
|
|
//
|
|
// Bit 3 of 0x3DA is set during vertical retrace. This is the original 1987 VGA
|
|
// interface and it still works on everything that emulates a VGA, QEMU's
|
|
// stdvga included -- VBE's own protected-mode interface for this is optional
|
|
// and frequently absent, so the old port is the portable answer.
|
|
//
|
|
// Two loops, not one: waiting only for the flag to *be* set would return
|
|
// immediately if a retrace is already in progress, having just missed the
|
|
// start of it. Waiting for the current one to end and the next to begin is
|
|
// what actually lands the blit between frames.
|
|
//
|
|
// The counters are a deadlock guard. On hardware that never reports retrace
|
|
// this returns after a bounded spin instead of hanging the caller forever,
|
|
// which matters because this can be called with the console locked.
|
|
static void
|
|
vga_disp_wait_vblank(struct device *d)
|
|
{
|
|
int guard;
|
|
|
|
for (guard = 0; guard < 1000000; guard++)
|
|
if (!(inb(0x3DA) & 0x08))
|
|
break;
|
|
for (guard = 0; guard < 1000000; guard++)
|
|
if (inb(0x3DA) & 0x08)
|
|
break;
|
|
}
|
|
|
|
const struct display_ops vga_display_ops = {
|
|
.mode = vga_disp_mode,
|
|
.acquire = vga_disp_acquire,
|
|
.present = vga_disp_present,
|
|
.wait_vblank = vga_disp_wait_vblank,
|
|
};
|