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Message-ID: <CALCETrXYtQUtLU-wF5YCxY9ZfNCDMZo1614Tg+FhcybPnCj4kw@mail.gmail.com>
Date: Sun, 26 Jun 2016 17:23:00 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Brian Gerst <brgerst@...il.com>
Cc: Andy Lutomirski <luto@...nel.org>,
"the arch/x86 maintainers" <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
Borislav Petkov <bp@...en8.de>,
Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>,
"kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jann Horn <jann@...jh.net>,
Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v4 22/29] x86/asm: Move 'status' from struct thread_info
to struct thread_struct
On Sun, Jun 26, 2016 at 4:55 PM, Brian Gerst <brgerst@...il.com> wrote:
> On Sun, Jun 26, 2016 at 5:55 PM, Andy Lutomirski <luto@...nel.org> wrote:
>> Becuase sched.h and thread_info.h are a tangled mess, I turned
>> in_compat_syscall into a macro. If we had current_thread_struct()
>> or similar and we could use it from thread_info.h, then this would
>> be a bit cleaner.
>>
>> Signed-off-by: Andy Lutomirski <luto@...nel.org>
>> ---
>> arch/x86/entry/common.c | 4 ++--
>> arch/x86/include/asm/processor.h | 12 ++++++++++++
>> arch/x86/include/asm/syscall.h | 23 +++++------------------
>> arch/x86/include/asm/thread_info.h | 23 ++++-------------------
>> arch/x86/kernel/asm-offsets.c | 1 -
>> arch/x86/kernel/fpu/init.c | 1 -
>> arch/x86/kernel/process_64.c | 4 ++--
>> arch/x86/kernel/ptrace.c | 2 +-
>> 8 files changed, 26 insertions(+), 44 deletions(-)
>>
>> diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
>> index ec138e538c44..c4150bec7982 100644
>> --- a/arch/x86/entry/common.c
>> +++ b/arch/x86/entry/common.c
>> @@ -271,7 +271,7 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
>> * syscalls. The fixup is exercised by the ptrace_syscall_32
>> * selftest.
>> */
>> - ti->status &= ~TS_COMPAT;
>> + current->thread.status &= ~TS_COMPAT;
>> #endif
>>
>> user_enter();
>> @@ -369,7 +369,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
>> unsigned int nr = (unsigned int)regs->orig_ax;
>>
>> #ifdef CONFIG_IA32_EMULATION
>> - ti->status |= TS_COMPAT;
>> + current->thread.status |= TS_COMPAT;
>> #endif
>>
>> if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
>> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
>> index a2e20d6d01fe..a75e720f6402 100644
>> --- a/arch/x86/include/asm/processor.h
>> +++ b/arch/x86/include/asm/processor.h
>> @@ -388,6 +388,9 @@ struct thread_struct {
>> unsigned short fsindex;
>> unsigned short gsindex;
>> #endif
>> +
>> + u32 status; /* thread synchronous flags */
>> +
>> #ifdef CONFIG_X86_32
>> unsigned long ip;
>> #endif
>> @@ -437,6 +440,15 @@ struct thread_struct {
>> };
>>
>> /*
>> + * Thread-synchronous status.
>> + *
>> + * This is different from the flags in that nobody else
>> + * ever touches our thread-synchronous status, so we don't
>> + * have to worry about atomic accesses.
>> + */
>> +#define TS_COMPAT 0x0002 /* 32bit syscall active (64BIT)*/
>> +
>> +/*
>> * Set IOPL bits in EFLAGS from given mask
>> */
>> static inline void native_set_iopl_mask(unsigned mask)
>> diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
>> index 999b7cd2e78c..17229e7e2a1c 100644
>> --- a/arch/x86/include/asm/syscall.h
>> +++ b/arch/x86/include/asm/syscall.h
>> @@ -60,7 +60,7 @@ static inline long syscall_get_error(struct task_struct *task,
>> * TS_COMPAT is set for 32-bit syscall entries and then
>> * remains set until we return to user mode.
>> */
>> - if (task_thread_info(task)->status & TS_COMPAT)
>> + if (task->thread.status & TS_COMPAT)
>> /*
>> * Sign-extend the value so (int)-EFOO becomes (long)-EFOO
>> * and will match correctly in comparisons.
>> @@ -116,7 +116,7 @@ static inline void syscall_get_arguments(struct task_struct *task,
>> unsigned long *args)
>> {
>> # ifdef CONFIG_IA32_EMULATION
>> - if (task_thread_info(task)->status & TS_COMPAT)
>> + if (task->thread.status & TS_COMPAT)
>> switch (i) {
>> case 0:
>> if (!n--) break;
>> @@ -177,7 +177,7 @@ static inline void syscall_set_arguments(struct task_struct *task,
>> const unsigned long *args)
>> {
>> # ifdef CONFIG_IA32_EMULATION
>> - if (task_thread_info(task)->status & TS_COMPAT)
>> + if (task->thread.status & TS_COMPAT)
>> switch (i) {
>> case 0:
>> if (!n--) break;
>> @@ -234,21 +234,8 @@ static inline void syscall_set_arguments(struct task_struct *task,
>>
>> static inline int syscall_get_arch(void)
>> {
>> -#ifdef CONFIG_IA32_EMULATION
>> - /*
>> - * TS_COMPAT is set for 32-bit syscall entry and then
>> - * remains set until we return to user mode.
>> - *
>> - * TIF_IA32 tasks should always have TS_COMPAT set at
>> - * system call time.
>> - *
>> - * x32 tasks should be considered AUDIT_ARCH_X86_64.
>> - */
>> - if (task_thread_info(current)->status & TS_COMPAT)
>> - return AUDIT_ARCH_I386;
>> -#endif
>> - /* Both x32 and x86_64 are considered "64-bit". */
>> - return AUDIT_ARCH_X86_64;
>> + /* x32 tasks should be considered AUDIT_ARCH_X86_64. */
>> + return in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
>> }
>> #endif /* CONFIG_X86_32 */
>>
>> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
>> index b45ffdda3549..7b42c1e462ac 100644
>> --- a/arch/x86/include/asm/thread_info.h
>> +++ b/arch/x86/include/asm/thread_info.h
>> @@ -55,7 +55,6 @@ struct task_struct;
>> struct thread_info {
>> struct task_struct *task; /* main task structure */
>> __u32 flags; /* low level flags */
>> - __u32 status; /* thread synchronous flags */
>> __u32 cpu; /* current CPU */
>> };
>>
>> @@ -211,28 +210,14 @@ static inline unsigned long current_stack_pointer(void)
>>
>> #endif
>>
>> -/*
>> - * Thread-synchronous status.
>> - *
>> - * This is different from the flags in that nobody else
>> - * ever touches our thread-synchronous status, so we don't
>> - * have to worry about atomic accesses.
>> - */
>> -#define TS_COMPAT 0x0002 /* 32bit syscall active (64BIT)*/
>> -
>> #ifndef __ASSEMBLY__
>>
>> -static inline bool in_ia32_syscall(void)
>> -{
>> #ifdef CONFIG_X86_32
>> - return true;
>> -#endif
>> -#ifdef CONFIG_IA32_EMULATION
>> - if (current_thread_info()->status & TS_COMPAT)
>> - return true;
>> +#define in_ia32_syscall() true
>> +#else
>> +#define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
>> + current->thread.status & TS_COMPAT)
>> #endif
>> - return false;
>> -}
>>
>> /*
>> * Force syscall return via IRET by making it look as if there was
>> diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
>> index 2bd5c6ff7ee7..a91a6ead24a2 100644
>> --- a/arch/x86/kernel/asm-offsets.c
>> +++ b/arch/x86/kernel/asm-offsets.c
>> @@ -30,7 +30,6 @@
>> void common(void) {
>> BLANK();
>> OFFSET(TI_flags, thread_info, flags);
>> - OFFSET(TI_status, thread_info, status);
>
> TI_status can be deleted. It's last users were removed in commit ee08c6bd.
Indeed.
Just to double-check: are you saying that this patch is okay?
--Andy
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