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Commit 385eca8f authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/asm/32: Make pt_regs's segment registers be 16 bits 



Many 32-bit x86 CPUs do 16-bit writes when storing segment registers to
memory.  This can cause the high word of regs->[cdefgs]s to
occasionally contain garbage.

Rather than making the entry code more complicated to fix up the
garbage, just change pt_regs to reflect reality.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 21ec3bf6

arch/x86/include/asm/ptrace.h

+26 −6
Original line number Original line Diff line number Diff line
@@ -9,6 +9,20 @@ 
#ifdef __i386__

#ifdef __i386__





struct pt_regs {

struct pt_regs {

	/*

	 * NB: 32-bit x86 CPUs are inconsistent as what happens in the

	 * following cases (where %seg represents a segment register):

	 *

	 * - pushl %seg: some do a 16-bit write and leave the high

	 *   bits alone

	 * - movl %seg, [mem]: some do a 16-bit write despite the movl

	 * - IDT entry: some (e.g. 486) will leave the high bits of CS

	 *   and (if applicable) SS undefined.

	 *

	 * Fortunately, x86-32 doesn't read the high bits on POP or IRET,

	 * so we can just treat all of the segment registers as 16-bit

	 * values.

	 */

	unsigned long bx;

	unsigned long bx;

	unsigned long cx;

	unsigned long cx;

	unsigned long dx;

	unsigned long dx;
@@ -16,16 +30,22 @@ struct pt_regs { 
	unsigned long di;

	unsigned long di;

	unsigned long bp;

	unsigned long bp;

	unsigned long ax;

	unsigned long ax;

	unsigned long ds;

	unsigned short ds;

	unsigned long es;

	unsigned short __dsh;

	unsigned long fs;

	unsigned short es;

	unsigned long gs;

	unsigned short __esh;

	unsigned short fs;

	unsigned short __fsh;

	unsigned short gs;

	unsigned short __gsh;

	unsigned long orig_ax;

	unsigned long orig_ax;

	unsigned long ip;

	unsigned long ip;

	unsigned long cs;

	unsigned short cs;

	unsigned short __csh;

	unsigned long flags;

	unsigned long flags;

	unsigned long sp;

	unsigned long sp;

	unsigned long ss;

	unsigned short ss;

	unsigned short __ssh;

};

};





#else /* __i386__ */

#else /* __i386__ */