Commit e696c231 authored by Chang S. Bae's avatar Chang S. Bae Committed by Ingo Molnar
Browse files

x86/fsgsbase/64: Make ptrace use the new FS/GS base helpers 



Use the new FS/GS base helper functions in <asm/fsgsbase.h> in the platform
specific ptrace implementation of the following APIs:

  PTRACE_ARCH_PRCTL,
  PTRACE_SETREG,
  PTRACE_GETREG,
  etc.

The fsgsbase code is more abstracted out this way and the FS/GS-update
mechanism will be easier to change this way.

[ mingo: Wrote new changelog. ]

Based-on-code-from: Andy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarChang S. Bae <chang.seok.bae@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Markus T Metzger <markus.t.metzger@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537312139-5580-4-git-send-email-chang.seok.bae@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b1378a56

arch/x86/include/asm/fsgsbase.h

+0 −3
Original line number Diff line number Diff line
@@ -8,9 +8,6 @@ 


#include <asm/msr-index.h>



unsigned long x86_fsgsbase_read_task(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

arch/x86/kernel/process_64.c

+10 −39
Original line number Diff line number Diff line
@@ -287,7 +287,7 @@ static __always_inline void load_seg_legacy(unsigned short prev_index, 
	}

}



unsigned long x86_fsgsbase_read_task(struct task_struct *task,

static unsigned long x86_fsgsbase_read_task(struct task_struct *task,

					    unsigned short selector)

{

	unsigned short idx = selector >> 3;
@@ -751,54 +751,25 @@ 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 = x86_gsbase_write_task(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 = x86_fsbase_write_task(task, arg2);

		break;

	}

	case ARCH_GET_FS: {

		unsigned long base;

		unsigned long base = x86_fsbase_read_task(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 = x86_gsbase_read_task(task);



		if (doit)

			rdmsrl(MSR_KERNEL_GS_BASE, base);

		else

			base = task->thread.gsbase;

		ret = put_user(base, (unsigned long __user *)arg2);

		break;

	}

arch/x86/kernel/ptrace.c

+8 −19
Original line number Diff line number Diff line
@@ -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 x86_fsbase_write_task(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 x86_gsbase_write_task(child, value);

		return 0;

#endif

	}
@@ -435,20 +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 x86_fsgsbase_read_task(task,

						      task->thread.fsindex);

	}

	case offsetof(struct user_regs_struct, gs_base): {

		if (task->thread.gsindex == 0)

			return task->thread.gsbase;

		else

			return x86_fsgsbase_read_task(task,

						      task->thread.gsindex);

	}

	case offsetof(struct user_regs_struct, fs_base):

		return x86_fsbase_read_task(task);

	case offsetof(struct user_regs_struct, gs_base):

		return x86_gsbase_read_task(task);

#endif

	}

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