summaryrefslogtreecommitdiff
path: root/arch/x86/boot/tools
diff options
context:
space:
mode:
authorMatt Fleming <matt.fleming@intel.com>2012-04-15 16:06:04 +0100
committerH. Peter Anvin <hpa@linux.intel.com>2012-04-16 11:41:44 -0700
commitb1994304fc399f5d3a5368c81111d713490c4799 (patch)
treefda4b1fa900378abddf71bc8d815543a49783fee /arch/x86/boot/tools
parentd7de8649f34d45041409d1af4ba4a521971a9075 (diff)
x86, efi: Add dedicated EFI stub entry point
The method used to work out whether we were booted by EFI firmware or via a boot loader is broken. Because efi_main() is always executed when booting from a boot loader we will dereference invalid pointers either on the stack (CONFIG_X86_32) or contained in %rdx (CONFIG_X86_64) when searching for an EFI System Table signature. Instead of dereferencing these invalid system table pointers, add a new entry point that is only used when booting from EFI firmware, when we know the pointer arguments will be valid. With this change legacy boot loaders will no longer execute efi_main(), but will instead skip EFI stub initialisation completely. [ hpa: Marking this for urgent/stable since it is a regression when the option is enabled; without the option the patch has no effect ] Signed-off-by: Matt Fleming <matt.hfleming@intel.com> Link: http://lkml.kernel.org/r/1334584744.26997.14.camel@mfleming-mobl1.ger.corp.intel.com Reported-by: Jordan Justen <jordan.l.justen@intel.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: <stable@vger.kernel.org> v3.3
Diffstat (limited to 'arch/x86/boot/tools')
-rw-r--r--arch/x86/boot/tools/build.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index ed549767a231..24443a332083 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -205,8 +205,13 @@ int main(int argc, char ** argv)
put_unaligned_le32(file_sz, &buf[pe_header + 0x50]);
#ifdef CONFIG_X86_32
- /* Address of entry point */
- put_unaligned_le32(i, &buf[pe_header + 0x28]);
+ /*
+ * Address of entry point.
+ *
+ * The EFI stub entry point is +16 bytes from the start of
+ * the .text section.
+ */
+ put_unaligned_le32(i + 16, &buf[pe_header + 0x28]);
/* .text size */
put_unaligned_le32(file_sz, &buf[pe_header + 0xb0]);
@@ -217,9 +222,11 @@ int main(int argc, char ** argv)
/*
* Address of entry point. startup_32 is at the beginning and
* the 64-bit entry point (startup_64) is always 512 bytes
- * after.
+ * after. The EFI stub entry point is 16 bytes after that, as
+ * the first instruction allows legacy loaders to jump over
+ * the EFI stub initialisation
*/
- put_unaligned_le32(i + 512, &buf[pe_header + 0x28]);
+ put_unaligned_le32(i + 528, &buf[pe_header + 0x28]);
/* .text size */
put_unaligned_le32(file_sz, &buf[pe_header + 0xc0]);