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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: Chang 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Chang S. Bae 2018-09-18 16:08:54 -07:00 committed by Ingo Molnar
parent b1378a561f
commit e696c231be
3 changed files with 18 additions and 61 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/include/asm/fsgsbase.h
View File

@ -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

49
arch/x86/kernel/process_64.c
View File

@ -287,8 +287,8 @@ static __always_inline void load_seg_legacy(unsigned short prev_index,
}
}
unsigned long x86_fsgsbase_read_task(struct task_struct *task,
unsigned short selector)
static unsigned long x86_fsgsbase_read_task(struct task_struct *task,
unsigned short selector)
{
unsigned short idx = selector >> 3;
unsigned long base;
@ -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;
}

27
arch/x86/kernel/ptrace.c
View File

@ -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
}