75 lines
2.8 KiB
Diff
75 lines
2.8 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: "C. Masloch" <pushbx@38.de>
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Date: Thu, 1 Feb 2018 15:51:55 +0100
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Subject: [PATCH] chainloader: patch in BPB's sectors_per_track and num_heads
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These fields must reflect the ROM-BIOS's geometry for CHS-based
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loaders to correctly load their next stage. Most loaders do not
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query the ROM-BIOS (Int13.08), relying on the BPB fields to hold
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the correct values already.
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Tested with lDebug booted in qemu via grub2's
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FreeDOS direct loading support, refer to
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https://bitbucket.org/ecm/ldosboot + https://bitbucket.org/ecm/ldebug
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(For this test, lDebug's iniload.asm must be assembled with
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-D_QUERY_GEOMETRY=0 to leave the BPB values provided by grub.)
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Signed-off-by: C. Masloch <pushbx@38.de>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/loader/i386/pc/chainloader.c | 20 ++++++++++++++++++--
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1 file changed, 18 insertions(+), 2 deletions(-)
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diff --git a/grub-core/loader/i386/pc/chainloader.c b/grub-core/loader/i386/pc/chainloader.c
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index 18220b7aaab..ef3a322b78c 100644
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--- a/grub-core/loader/i386/pc/chainloader.c
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+++ b/grub-core/loader/i386/pc/chainloader.c
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@@ -19,6 +19,7 @@
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#include <grub/loader.h>
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#include <grub/machine/chainloader.h>
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+#include <grub/machine/biosdisk.h>
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#include <grub/machine/memory.h>
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#include <grub/file.h>
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#include <grub/err.h>
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@@ -86,9 +87,16 @@ grub_chainloader_unload (void)
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void
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grub_chainloader_patch_bpb (void *bs, grub_device_t dev, grub_uint8_t dl)
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{
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- grub_uint32_t part_start = 0;
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+ grub_uint32_t part_start = 0, heads = 0, sectors = 0;
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if (dev && dev->disk)
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- part_start = grub_partition_get_start (dev->disk->partition);
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+ {
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+ part_start = grub_partition_get_start (dev->disk->partition);
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+ if (dev->disk->data)
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+ {
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+ heads = ((struct grub_biosdisk_data *)(dev->disk->data))->heads;
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+ sectors = ((struct grub_biosdisk_data *)(dev->disk->data))->sectors;
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+ }
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+ }
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if (grub_memcmp ((char *) &((struct grub_ntfs_bpb *) bs)->oem_name,
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"NTFS", 4) == 0)
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{
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@@ -127,12 +135,20 @@ grub_chainloader_patch_bpb (void *bs, grub_device_t dev, grub_uint8_t dl)
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{
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bpb->num_hidden_sectors = grub_cpu_to_le32 (part_start);
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bpb->version_specific.fat12_or_fat16.num_ph_drive = dl;
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+ if (sectors)
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+ bpb->sectors_per_track = grub_cpu_to_le16 (sectors);
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+ if (heads)
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+ bpb->num_heads = grub_cpu_to_le16 (heads);
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return;
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}
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if (bpb->version_specific.fat32.sectors_per_fat_32)
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{
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bpb->num_hidden_sectors = grub_cpu_to_le32 (part_start);
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bpb->version_specific.fat32.num_ph_drive = dl;
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+ if (sectors)
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+ bpb->sectors_per_track = grub_cpu_to_le16 (sectors);
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+ if (heads)
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+ bpb->num_heads = grub_cpu_to_le16 (heads);
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return;
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}
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break;
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