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([2601:646:c200:1ef2:3602:86ff:fef6:e86b]) by smtp.googlemail.com with ESMTPSA id e1sm6479853pgv.82.2019.11.08.14.31.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Nov 2019 14:31:49 -0800 (PST) Subject: Re: [patch 2/9] x86/process: Unify copy_thread_tls() To: Thomas Gleixner , LKML Cc: x86@kernel.org, Stephen Hemminger , Willy Tarreau , Juergen Gross , Sean Christopherson , Linus Torvalds , "H. Peter Anvin" References: <20191106193459.581614484@linutronix.de> <20191106202805.948064985@linutronix.de> From: Andy Lutomirski Message-ID: <53a6f346-fca1-ac04-ee34-6d472a0d4408@kernel.org> Date: Fri, 8 Nov 2019 14:31:47 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20191106202805.948064985@linutronix.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/6/19 11:35 AM, Thomas Gleixner wrote: > While looking at the TSS io bitmap it turned out that any change in that > area would require identical changes to copy_thread_tls(). The 32 and 64 > bit variants share sufficient code to consolidate them into a common > function to avoid duplication of upcoming modifications. > > Signed-off-by: Thomas Gleixner > --- > arch/x86/include/asm/ptrace.h | 6 ++ > arch/x86/include/asm/switch_to.h | 10 ++++ > arch/x86/kernel/process.c | 94 +++++++++++++++++++++++++++++++++++++++ > arch/x86/kernel/process_32.c | 68 ---------------------------- > arch/x86/kernel/process_64.c | 75 ------------------------------- > 5 files changed, 110 insertions(+), 143 deletions(-) > > --- a/arch/x86/include/asm/ptrace.h > +++ b/arch/x86/include/asm/ptrace.h > @@ -361,5 +361,11 @@ extern int do_get_thread_area(struct tas > extern int do_set_thread_area(struct task_struct *p, int idx, > struct user_desc __user *info, int can_allocate); > > +#ifdef CONFIG_X86_64 > +# define do_set_thread_area_64(p, s, t) do_arch_prctl_64(p, s, t) > +#else > +# define do_set_thread_area_64(p, s, t) (0) > +#endif > + > #endif /* !__ASSEMBLY__ */ > #endif /* _ASM_X86_PTRACE_H */ > --- a/arch/x86/include/asm/switch_to.h > +++ b/arch/x86/include/asm/switch_to.h > @@ -103,7 +103,17 @@ static inline void update_task_stack(str > if (static_cpu_has(X86_FEATURE_XENPV)) > load_sp0(task_top_of_stack(task)); > #endif > +} > > +static inline void kthread_frame_init(struct inactive_task_frame *frame, > + unsigned long fun, unsigned long arg) > +{ > + frame->bx = fun; > +#ifdef CONFIG_X86_32 > + frame->di = arg; > +#else > + frame->r12 = arg; > +#endif > } > > #endif /* _ASM_X86_SWITCH_TO_H */ > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -132,6 +132,100 @@ void exit_thread(struct task_struct *tsk > fpu__drop(fpu); > } > > +static int set_new_tls(struct task_struct *p, unsigned long tls) > +{ > + struct user_desc __user *utls = (struct user_desc __user *)tls; > + > + if (in_ia32_syscall()) > + return do_set_thread_area(p, -1, utls, 0); > + else > + return do_set_thread_area_64(p, ARCH_SET_FS, tls); > +} > + > +static inline int copy_io_bitmap(struct task_struct *tsk) > +{ > + if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP))) > + return 0; > + > + tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr, > + IO_BITMAP_BYTES, GFP_KERNEL); tsk->thread.io_bitmap_max = current->thread.io_bitmap_max? I realize you inherited this from the code you're refactoring, but it does seem to be missing. > + if (!tsk->thread.io_bitmap_ptr) { > + tsk->thread.io_bitmap_max = 0; > + return -ENOMEM; > + } > + set_tsk_thread_flag(tsk, TIF_IO_BITMAP); > + return 0; > +} > + > +static inline void free_io_bitmap(struct task_struct *tsk) > +{ > + if (tsk->thread.io_bitmap_ptr) { > + kfree(tsk->thread.io_bitmap_ptr); > + tsk->thread.io_bitmap_ptr = NULL; > + tsk->thread.io_bitmap_max = 0; > + } > +} > + > +int copy_thread_tls(unsigned long clone_flags, unsigned long sp, > + unsigned long arg, struct task_struct *p, unsigned long tls) > +{ > + struct inactive_task_frame *frame; > + struct fork_frame *fork_frame; > + struct pt_regs *childregs; > + int ret; > + > + childregs = task_pt_regs(p); > + fork_frame = container_of(childregs, struct fork_frame, regs); > + frame = &fork_frame->frame; > + > + frame->bp = 0; > + frame->ret_addr = (unsigned long) ret_from_fork; > + p->thread.sp = (unsigned long) fork_frame; > + p->thread.io_bitmap_ptr = NULL; > + memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); > + > +#ifdef CONFIG_X86_64 > + savesegment(gs, p->thread.gsindex); > + p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase; > + savesegment(fs, p->thread.fsindex); > + p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase; > + savesegment(es, p->thread.es); > + savesegment(ds, p->thread.ds); > +#else > + /* Clear all status flags including IF and set fixed bit. */ > + frame->flags = X86_EFLAGS_FIXED; > +#endif Want to do another commit to make the eflags fixup unconditional? I'm wondering if we have a bug. Other than these questions: Acked-by: Andy Lutomirski