The FS/GS base helper functions are used on ptrace APIs (PTRACE_ARCH_PRCTL, PTRACE_SETREG, PTRACE_GETREG, etc). The FS/GS-update mechanism is now a bit organized.
Based-on-code-from: Andy Lutomirski <[email protected]> Signed-off-by: Chang S. Bae <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Andi Kleen <[email protected]> --- arch/x86/include/asm/fsgsbase.h | 2 -- arch/x86/kernel/process_64.c | 48 +++++++++-------------------------------- arch/x86/kernel/ptrace.c | 25 +++++++-------------- 3 files changed, 18 insertions(+), 57 deletions(-) diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h index 9dce8c0..f00a8a6 100644 --- a/arch/x86/include/asm/fsgsbase.h +++ b/arch/x86/include/asm/fsgsbase.h @@ -8,8 +8,6 @@ #include <asm/msr-index.h> -unsigned long task_seg_base(struct task_struct *task, unsigned short selector); - /* * Read/write a task's fsbase or gsbase. This returns the value that * the FS/GS base would have (if the task were to be resumed). These diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index ec76796..bf0bd5c 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -279,7 +279,8 @@ static __always_inline void load_seg_legacy(unsigned short prev_index, } } -unsigned long task_seg_base(struct task_struct *task, unsigned short selector) +static unsigned long task_seg_base(struct task_struct *task, + unsigned short selector) { unsigned short idx = selector >> 3; unsigned long base; @@ -741,54 +742,25 @@ static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr) long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) { int ret = 0; - int doit = task == current; - int cpu; switch (option) { - case ARCH_SET_GS: - if (arg2 >= TASK_SIZE_MAX) - return -EPERM; - cpu = get_cpu(); - task->thread.gsindex = 0; - task->thread.gsbase = arg2; - if (doit) { - load_gs_index(0); - ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, arg2); - } - put_cpu(); + case ARCH_SET_GS: { + ret = write_task_gsbase(task, arg2); break; - case ARCH_SET_FS: - /* Not strictly needed for fs, but do it for symmetry - with gs */ - if (arg2 >= TASK_SIZE_MAX) - return -EPERM; - cpu = get_cpu(); - task->thread.fsindex = 0; - task->thread.fsbase = arg2; - if (doit) { - /* set the selector to 0 to not confuse __switch_to */ - loadsegment(fs, 0); - ret = wrmsrl_safe(MSR_FS_BASE, arg2); - } - put_cpu(); + } + case ARCH_SET_FS: { + ret = write_task_fsbase(task, arg2); break; + } case ARCH_GET_FS: { - unsigned long base; + unsigned long base = read_task_fsbase(task); - if (doit) - rdmsrl(MSR_FS_BASE, base); - else - base = task->thread.fsbase; ret = put_user(base, (unsigned long __user *)arg2); break; } case ARCH_GET_GS: { - unsigned long base; + unsigned long base = read_task_gsbase(task); - if (doit) - rdmsrl(MSR_KERNEL_GS_BASE, base); - else - base = task->thread.gsbase; ret = put_user(base, (unsigned long __user *)arg2); break; } diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 7be53f9..d41d605 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -397,12 +397,11 @@ static int putreg(struct task_struct *child, if (value >= TASK_SIZE_MAX) return -EIO; /* - * When changing the segment base, use do_arch_prctl_64 - * to set either thread.fs or thread.fsindex and the - * corresponding GDT slot. + * When changing the FS base, use the same + * mechanism as for do_arch_prctl_64. */ if (child->thread.fsbase != value) - return do_arch_prctl_64(child, ARCH_SET_FS, value); + return write_task_fsbase(child, value); return 0; case offsetof(struct user_regs_struct,gs_base): /* @@ -411,7 +410,7 @@ static int putreg(struct task_struct *child, if (value >= TASK_SIZE_MAX) return -EIO; if (child->thread.gsbase != value) - return do_arch_prctl_64(child, ARCH_SET_GS, value); + return write_task_gsbase(child, value); return 0; #endif } @@ -435,18 +434,10 @@ static unsigned long getreg(struct task_struct *task, unsigned long offset) return get_flags(task); #ifdef CONFIG_X86_64 - case offsetof(struct user_regs_struct, fs_base): { - if (task->thread.fsindex == 0) - return task->thread.fsbase; - else - return task_seg_base(task, task->thread.fsindex); - } - case offsetof(struct user_regs_struct, gs_base): { - if (task->thread.gsindex == 0) - return task->thread.gsbase; - else - return task_seg_base(task, task->thread.gsindex); - } + case offsetof(struct user_regs_struct, fs_base): + return read_task_fsbase(task); + case offsetof(struct user_regs_struct, gs_base): + return read_task_gsbase(task); #endif } -- 2.7.4
