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display: a 64-bit framebuffer address, no mirroring onto itself

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Three fixes for real machines that broke at any resolution but 800x600:

- kmain() took the loader's framebuffer address as uint32, and
  vga_fb_init() re-published the scanout from that and the 16-bit VBE
  block. An aperture above 4 GB moved the console onto the wrong memory
  right after the vga: line. Both now use the loader's 64-bit display
  block, mapped with ioremap().
- The loader mirrored onto the console splitter's GOP, which forwards to
  the primary itself, and onto GOPs that share the primary's aperture.
  After a mode change that rewrote the screen over itself with another
  mode's stride. Handles without a device path and overlapping apertures
  are skipped, and a mode change re-matches the remaining mirrors.
- A mode whose reported size, stride or aperture does not add up after
  SetMode is refused, and the loader returns to the previous one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
This commit is contained in:
Nexoniarz 2026-10-23 15:46:42 +02:00
commit fe32833ade
5 changed files with 193 additions and 16 deletions
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44
kernel/drivers/gpu/vga/vga_fb.c
View file

@ -69,15 +69,29 @@ vga_fb_init(uint64 phys_addr)
{
struct fb_info info;
if (phys_addr == 0)
phys_addr = *(uint32*)(P2V(SCHBOOT_VBE_LFB));
fb = (volatile uchar*)P2V(phys_addr);
fb_phys = phys_addr;
fb_stride = *(ushort*)(P2V(SCHBOOT_VBE_STRIDE));
fb_width = *(ushort*)(P2V(SCHBOOT_VBE_WIDTH));
fb_height = *(ushort*)(P2V(SCHBOOT_VBE_HEIGHT));
fb_bpp = *(uchar*)(P2V(SCHBOOT_VBE_BPP));
// The UEFI loader's display block first, and the VBE block only without it.
//
// This read the VBE block alone, which is a BIOS structure: a 32-bit
// address and 16-bit sizes. kmain() reads the loader's block and puts the
// console on the right framebuffer; this then re-published the scanout from
// the other one, so the two disagreed on any machine the VBE block cannot
// describe, and the second one won.
uint64 blk = *(uint64*)P2V(SCHBOOT_FB_BASE);
if (blk) {
phys_addr = blk;
fb_stride = *(uint32*)P2V(SCHBOOT_FB_STRIDE);
fb_width = *(uint32*)P2V(SCHBOOT_FB_WIDTH);
fb_height = *(uint32*)P2V(SCHBOOT_FB_HEIGHT);
fb_bpp = 32;
} else {
if (phys_addr == 0)
phys_addr = *(uint32*)(P2V(SCHBOOT_VBE_LFB));
fb_stride = *(ushort*)(P2V(SCHBOOT_VBE_STRIDE));
fb_width = *(ushort*)(P2V(SCHBOOT_VBE_WIDTH));
fb_height = *(ushort*)(P2V(SCHBOOT_VBE_HEIGHT));
fb_bpp = *(uchar*)(P2V(SCHBOOT_VBE_BPP));
}
fb_phys = phys_addr;
if (fb_width == 0) fb_width = 800;
if (fb_height == 0) fb_height = 600;
@ -100,8 +114,16 @@ vga_fb_init(uint64 phys_addr)
return;
}
kinfo("vga: %dx%d, %d bpp, stride %d, LFB: 0x%x\n",
fb_width, fb_height, fb_bpp, fb_stride, (uint32)phys_addr);
// ioremap() rather than P2V(): the same address below 4 GB, and the window
// kmain() already opened for an aperture above it.
fb = (volatile uchar*)ioremap(phys_addr, (uint64)fb_stride * fb_height);
if (fb == 0) {
cprintf("vga: cannot map the framebuffer at %p\n", (void *)phys_addr);
return;
}
kinfo("vga: %dx%d, %d bpp, stride %d, LFB: %p\n",
fb_width, fb_height, fb_bpp, fb_stride, (void *)phys_addr);
info.ptr = fb;
info.phys = fb_phys;