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Date: Sun, 26 Jun 2016 19:55:31 -0400
From: Brian Gerst <brgerst@...il.com>
To: Andy Lutomirski <luto@...nel.org>
Cc: "the arch/x86 maintainers" <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 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 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.
--
Brian Gerst
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