diff options
| author | Andy Lutomirski <luto@kernel.org> | 2017-07-28 06:00:30 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-07-30 12:04:40 +0200 |
| commit | 385eca8f277c4c34f361a4c3a088fd876d29ae21 (patch) | |
| tree | 741009fbb9b67a8d6934b087f71b474784cfe107 /arch/x86/include/asm/ptrace.h | |
| parent | 21ec3bf6aeb4033210747837421e63286ba32646 (diff) | |
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: Andy 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: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/ptrace.h')
| -rw-r--r-- | arch/x86/include/asm/ptrace.h | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 2b5d686ea9f3..a29f82871699 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -9,6 +9,20 @@ #ifdef __i386__ 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 cx; unsigned long dx; @@ -16,16 +30,22 @@ struct pt_regs { unsigned long di; unsigned long bp; unsigned long ax; - unsigned long ds; - unsigned long es; - unsigned long fs; - unsigned long gs; + unsigned short ds; + unsigned short __dsh; + unsigned short es; + unsigned short __esh; + unsigned short fs; + unsigned short __fsh; + unsigned short gs; + unsigned short __gsh; unsigned long orig_ax; unsigned long ip; - unsigned long cs; + unsigned short cs; + unsigned short __csh; unsigned long flags; unsigned long sp; - unsigned long ss; + unsigned short ss; + unsigned short __ssh; }; #else /* __i386__ */ |