[tip: x86/urgent] x86/iopl: Make 'struct tss_struct' constant size again

[tip-bot2 for Ingo Molnar]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     0bcd7762727dd8ba9b9b6f828e5a4cbd5da4f725
Gitweb:        https://git.kernel.org/tip/0bcd7762727dd8ba9b9b6f828e5a4cbd5da4f725
Author:        Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate:    Tue, 26 Nov 2019 21:49:04 +01:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 26 Nov 2019 21:49:04 +01:00

x86/iopl: Make 'struct tss_struct' constant size again

After the following commit:

  05b042a19443: ("x86/pti/32: Calculate the various PTI cpu_entry_area sizes correctly, make the CPU_ENTRY_AREA_PAGES assert precise")

'struct cpu_entry_area' has to be Kconfig invariant, so that we always
have a matching CPU_ENTRY_AREA_PAGES size.

This commit added a CONFIG_X86_IOPL_IOPERM dependency to tss_struct:

  111e7b15cf10: ("x86/ioperm: Extend IOPL config to control ioperm() as well")

Which, if CONFIG_X86_IOPL_IOPERM is turned off, reduces the size of
cpu_entry_area by two pages, triggering the assert:

  ./include/linux/compiler.h:391:38: error: call to â__compiletime_assert_202â declared with attribute error: BUILD_BUG_ON failed: (CPU_ENTRY_AREA_PAGES+1)*PAGE_SIZE != CPU_ENTRY_AREA_MAP_SIZE

Simplify the Kconfig dependencies and make cpu_entry_area constant
size on 32-bit kernels again.

Fixes: 05b042a19443: ("x86/pti/32: Calculate the various PTI cpu_entry_area sizes correctly, make the CPU_ENTRY_AREA_PAGES assert precise")
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/include/asm/processor.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b4e29d8..e51afbb 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -411,9 +411,7 @@ struct tss_struct {
 	 */
 	struct x86_hw_tss	x86_tss;
 
-#ifdef CONFIG_X86_IOPL_IOPERM
 	struct x86_io_bitmap	io_bitmap;
-#endif
 } __aligned(PAGE_SIZE);
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);