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x86/iopl: Make 'struct tss_struct' constant size again
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After the following commit:

  05b042a: ("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:

  111e7b1: ("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 ‘__compiletime_assert_202’ 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: 05b042a: ("x86/pti/32: Calculate the various PTI cpu_entry_area sizes correctly, make the CPU_ENTRY_AREA_PAGES assert precise")
Cc: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Ingo Molnar committed Nov 26, 2019
1 parent 2be7d34 commit 0bcd776
Showing 1 changed file with 0 additions and 2 deletions.
2 changes: 0 additions & 2 deletions arch/x86/include/asm/processor.h
Original file line number Diff line number Diff line change
@@ -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);

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