diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/fsgsbase.h | 15 | ||||
| -rw-r--r-- | arch/x86/kernel/process_64.c | 99 | ||||
| -rw-r--r-- | arch/x86/kernel/ptrace.c | 9 |
3 files changed, 71 insertions, 52 deletions
diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h index eb377b6e9eed..bca4c743de77 100644 --- a/arch/x86/include/asm/fsgsbase.h +++ b/arch/x86/include/asm/fsgsbase.h @@ -16,8 +16,8 @@ */ extern unsigned long x86_fsbase_read_task(struct task_struct *task); extern unsigned long x86_gsbase_read_task(struct task_struct *task); -extern int x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase); -extern int x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase); +extern void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase); +extern void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase); /* Helper functions for reading/writing FS/GS base */ @@ -39,8 +39,15 @@ static inline unsigned long x86_gsbase_read_cpu_inactive(void) return gsbase; } -extern void x86_fsbase_write_cpu(unsigned long fsbase); -extern void x86_gsbase_write_cpu_inactive(unsigned long gsbase); +static inline void x86_fsbase_write_cpu(unsigned long fsbase) +{ + wrmsrl(MSR_FS_BASE, fsbase); +} + +static inline void x86_gsbase_write_cpu_inactive(unsigned long gsbase) +{ + wrmsrl(MSR_KERNEL_GS_BASE, gsbase); +} #endif /* CONFIG_X86_64 */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index bbfbf017065c..ddd4fa718c43 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -339,24 +339,6 @@ static unsigned long x86_fsgsbase_read_task(struct task_struct *task, return base; } -void x86_fsbase_write_cpu(unsigned long fsbase) -{ - /* - * Set the selector to 0 as a notion, that the segment base is - * overwritten, which will be checked for skipping the segment load - * during context switch. - */ - loadseg(FS, 0); - wrmsrl(MSR_FS_BASE, fsbase); -} - -void x86_gsbase_write_cpu_inactive(unsigned long gsbase) -{ - /* Set the selector to 0 for the same reason as %fs above. */ - loadseg(GS, 0); - wrmsrl(MSR_KERNEL_GS_BASE, gsbase); -} - unsigned long x86_fsbase_read_task(struct task_struct *task) { unsigned long fsbase; @@ -385,38 +367,18 @@ unsigned long x86_gsbase_read_task(struct task_struct *task) return gsbase; } -int x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase) +void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase) { - /* - * Not strictly needed for %fs, but do it for symmetry - * with %gs - */ - if (unlikely(fsbase >= TASK_SIZE_MAX)) - return -EPERM; + WARN_ON_ONCE(task == current); - preempt_disable(); task->thread.fsbase = fsbase; - if (task == current) - x86_fsbase_write_cpu(fsbase); - task->thread.fsindex = 0; - preempt_enable(); - - return 0; } -int x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase) +void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase) { - if (unlikely(gsbase >= TASK_SIZE_MAX)) - return -EPERM; + WARN_ON_ONCE(task == current); - preempt_disable(); task->thread.gsbase = gsbase; - if (task == current) - x86_gsbase_write_cpu_inactive(gsbase); - task->thread.gsindex = 0; - preempt_enable(); - - return 0; } int copy_thread_tls(unsigned long clone_flags, unsigned long sp, @@ -754,11 +716,60 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) switch (option) { case ARCH_SET_GS: { - ret = x86_gsbase_write_task(task, arg2); + if (unlikely(arg2 >= TASK_SIZE_MAX)) + return -EPERM; + + preempt_disable(); + /* + * ARCH_SET_GS has always overwritten the index + * and the base. Zero is the most sensible value + * to put in the index, and is the only value that + * makes any sense if FSGSBASE is unavailable. + */ + if (task == current) { + loadseg(GS, 0); + x86_gsbase_write_cpu_inactive(arg2); + + /* + * On non-FSGSBASE systems, save_base_legacy() expects + * that we also fill in thread.gsbase. + */ + task->thread.gsbase = arg2; + + } else { + task->thread.gsindex = 0; + x86_gsbase_write_task(task, arg2); + } + preempt_enable(); break; } case ARCH_SET_FS: { - ret = x86_fsbase_write_task(task, arg2); + /* + * Not strictly needed for %fs, but do it for symmetry + * with %gs + */ + if (unlikely(arg2 >= TASK_SIZE_MAX)) + return -EPERM; + + preempt_disable(); + /* + * Set the selector to 0 for the same reason + * as %gs above. + */ + if (task == current) { + loadseg(FS, 0); + x86_fsbase_write_cpu(arg2); + + /* + * On non-FSGSBASE systems, save_base_legacy() expects + * that we also fill in thread.fsbase. + */ + task->thread.fsbase = arg2; + } else { + task->thread.fsindex = 0; + x86_fsbase_write_task(task, arg2); + } + preempt_enable(); break; } case ARCH_GET_FS: { diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index ffae9b9740fd..4b8ee05dd6ad 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -397,11 +397,12 @@ static int putreg(struct task_struct *child, if (value >= TASK_SIZE_MAX) return -EIO; /* - * When changing the FS base, use the same - * mechanism as for do_arch_prctl_64(). + * When changing the FS base, use do_arch_prctl_64() + * to set the index to zero and to set the base + * as requested. */ if (child->thread.fsbase != value) - return x86_fsbase_write_task(child, value); + return do_arch_prctl_64(child, ARCH_SET_FS, value); return 0; case offsetof(struct user_regs_struct,gs_base): /* @@ -410,7 +411,7 @@ static int putreg(struct task_struct *child, if (value >= TASK_SIZE_MAX) return -EIO; if (child->thread.gsbase != value) - return x86_gsbase_write_task(child, value); + return do_arch_prctl_64(child, ARCH_SET_GS, value); return 0; #endif } |