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authorSamuel Thibault <samuel.thibault@ens-lyon.org>2014-07-06 18:49:55 +0200
committerSamuel Thibault <samuel.thibault@ens-lyon.org>2014-07-06 18:49:55 +0200
commit859c342d11a2d018e7b220e955bbe1ba1940f02f (patch)
tree1890b0757459549938be3ee5f2d23fcdcc94b019 /i386/i386at
parent97447914d6dcc32ada4ee028e1e2bab262501316 (diff)
Do not unmap page 0 when not needed
Since we need it to access some BIOS information, e.g. at ACPI shutdown. When the kernel VM is not starting at 0, there is already nothing mapped there in user tasks, anyway. * i386/i386at/model_dep.c (machine_init) [VM_MIN_KERNEL_ADDRESS != 0]: Do not call pmap_unmap_page_zero. * i386/intel/pmap.c (pmap_unmap_page_zero): Warn that unmapping page zero may break some BIOS functions.
Diffstat (limited to 'i386/i386at')
-rw-r--r--i386/i386at/acpi.c3
-rw-r--r--i386/i386at/model_dep.c4
2 files changed, 7 insertions, 0 deletions
diff --git a/i386/i386at/acpi.c b/i386/i386at/acpi.c
index ec8aeb1..986b3a2 100644
--- a/i386/i386at/acpi.c
+++ b/i386/i386at/acpi.c
@@ -55,8 +55,11 @@ grub_machine_acpi_get_rsdpv2 (void)
grub_uint8_t *ebda, *ptr;
grub_dprintf ("acpi", "Looking for RSDP. Scanning EBDA\n");
+ printf("ptr is %p\n", (* ((grub_uint16_t *) phystokv (0x40e))) << 4);
+ printf("len is %u\n", *( (grub_uint16_t *) phystokv ((* ((grub_uint16_t *) phystokv (0x40e))) << 4)));
ebda = (grub_uint8_t *) phystokv ((* ((grub_uint16_t *) phystokv (0x40e))) << 4);
ebda_len = * (grub_uint16_t *) ebda;
+ printf("EBDA len %d\n", ebda_len);
if (! ebda_len)
return 0;
for (ptr = ebda; ptr < ebda + 0x400; ptr += 16)
diff --git a/i386/i386at/model_dep.c b/i386/i386at/model_dep.c
index 6093a66..209cfb1 100644
--- a/i386/i386at/model_dep.c
+++ b/i386/i386at/model_dep.c
@@ -180,10 +180,14 @@ void machine_init(void)
*(unsigned short *)phystokv(0x472) = 0x1234;
#endif /* MACH_HYP */
+#if VM_MIN_KERNEL_ADDRESS == 0
/*
* Unmap page 0 to trap NULL references.
+ *
+ * Note that this breaks accessing some BIOS areas stored there.
*/
pmap_unmap_page_zero();
+#endif
}
/* Conserve power on processor CPU. */