From bb20921d00c770cb30bb85a300423d9062a94d91 Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Sun, 8 Nov 2026 07:49:23 +0800
Subject: [mubios] Multi-sector INT 13h AH=42h

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>
---
 mubios/core/post.c      |  2 +-
 mubios/drivers/ata.c    | 24 ++++++++++++++++++++++--
 mubios/include/bios.h   |  2 +-
 mubios/services/int13.c |  9 ++++++---
 4 files changed, 30 insertions(+), 7 deletions(-)

(limited to 'mubios')

diff --git a/mubios/core/post.c b/mubios/core/post.c
index 076d262..2af797b 100644
--- a/mubios/core/post.c
+++ b/mubios/core/post.c
@@ -40,7 +40,7 @@ post_main (void)
   u8 ata_status;
 
   mbr = (volatile u8 *)0x00007C00u;
-  ata_status = ata_read_sector28 (0, (u16 *)mbr);
+  ata_status = ata_read_sectors28 (0, (u16 *)mbr, 1);
 
   if (ata_status == 0 && mbr[0x01FE] == 0x55 && mbr[0x01FF] == 0xAA)
     serial_write ("mubios: MBR loaded\r\n");
diff --git a/mubios/drivers/ata.c b/mubios/drivers/ata.c
index a0cd12a..928a7d1 100644
--- a/mubios/drivers/ata.c
+++ b/mubios/drivers/ata.c
@@ -60,8 +60,8 @@ ata_delay_400ns (void)
   io_in8 (ATA_STATUS);
 }
 
-u8
-ata_read_sector28 (u32 lba, u16 *buffer)
+static u8
+ata_read_one_sector28 (u32 lba, u16 *buffer)
 {
   u8 status;
   u16 index;
@@ -91,3 +91,23 @@ ata_read_sector28 (u32 lba, u16 *buffer)
 
   return 0;
 }
+
+u8
+ata_read_sectors28 (u32 lba, u16 *buffer, u16 count)
+{
+  u16 sector;
+
+  if (count == 0u)
+    return 1;
+
+  for (sector = 0; sector < count; ++sector)
+    {
+      if (ata_read_one_sector28 (lba, buffer) != 0)
+        return 1;
+
+      lba++;
+      buffer += 256;
+    }
+
+  return 0;
+}
diff --git a/mubios/include/bios.h b/mubios/include/bios.h
index 29743e0..9c14a42 100644
--- a/mubios/include/bios.h
+++ b/mubios/include/bios.h
@@ -50,7 +50,7 @@ void ioapic_init (void);
 
 void ivt_init (void);
 
-u8 ata_read_sector28 (u32 lba, u16 *buffer);
+u8 ata_read_sectors28 (u32 lba, u16 *buffer, u16 count);
 
 struct bios_regs;
 
diff --git a/mubios/services/int13.c b/mubios/services/int13.c
index 078fa03..e5cef43 100644
--- a/mubios/services/int13.c
+++ b/mubios/services/int13.c
@@ -79,8 +79,9 @@ int13_service (struct bios_regs *regs)
     {
       packet = get_edd_packet (regs);
 
-      if (packet->size != 0x10u || packet->count != 1u
-          || packet->lba_high != 0u || packet->lba_low > 0x0FFFFFFFu)
+      if (packet->size != 0x10u || packet->count == 0u || packet->count > 127u
+          || packet->lba_high != 0u
+          || packet->lba_low > 0x10000000u - (u32)packet->count)
         {
           int13_fail (regs);
           return;
@@ -89,7 +90,9 @@ int13_service (struct bios_regs *regs)
       buffer_address
           = ((u32)packet->buffer_segment << 4) + packet->buffer_offset;
 
-      if (ata_read_sector28 (packet->lba_low, (u16 *)buffer_address) != 0)
+      if (ata_read_sectors28 (packet->lba_low, (u16 *)buffer_address,
+                              packet->count)
+          != 0)
         {
           int13_fail (regs);
           return;
-- 
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