4.19-stable review patch. If anyone has any objections, please let me know.
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From: Kirill A. Shutemov kirill.shutemov@linux.intel.com
commit 6f913de3231e1d70a871135b38219da7810df218 upstream.
EFI systems do not necessarily provide a legacy ROM. If the ROM is missing the memory is not mapped at all.
Trying to dereference values in the legacy ROM area leads to a crash on Macbook Pro.
Only look for values in the legacy ROM area for non-EFI system.
Fixes: 3548e131ec6a ("x86/boot/compressed/64: Find a place for 32-bit trampoline") Reported-by: Pitam Mitra pitamm@gmail.com Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Bockjoo Kim bockjoo@phys.ufl.edu Cc: bp@alien8.de Cc: hpa@zytor.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190219075224.35058-1-kirill.shutemov@linux.intel... Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202351 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/boot/compressed/pgtable_64.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)
--- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -1,5 +1,7 @@ +#include <linux/efi.h> #include <asm/e820/types.h> #include <asm/processor.h> +#include <asm/efi.h> #include "pgtable.h" #include "../string.h"
@@ -37,9 +39,10 @@ int cmdline_find_option_bool(const char
static unsigned long find_trampoline_placement(void) { - unsigned long bios_start, ebda_start; + unsigned long bios_start = 0, ebda_start = 0; unsigned long trampoline_start; struct boot_e820_entry *entry; + char *signature; int i;
/* @@ -47,8 +50,18 @@ static unsigned long find_trampoline_pla * This code is based on reserve_bios_regions(). */
- ebda_start = *(unsigned short *)0x40e << 4; - bios_start = *(unsigned short *)0x413 << 10; + /* + * EFI systems may not provide legacy ROM. The memory may not be mapped + * at all. + * + * Only look for values in the legacy ROM for non-EFI system. + */ + signature = (char *)&boot_params->efi_info.efi_loader_signature; + if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) && + strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) { + ebda_start = *(unsigned short *)0x40e << 4; + bios_start = *(unsigned short *)0x413 << 10; + }
if (bios_start < BIOS_START_MIN || bios_start > BIOS_START_MAX) bios_start = BIOS_START_MAX;