xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

x86/fsgsbase/64: Introduce FS/GS base helper functions

Browse Source 
Introduce FS/GS base access functionality via <asm/fsgsbase.h>,
not yet used by anything directly.

Factor out task_seg_base() from x86/ptrace.c and rename it to
x86_fsgsbase_read_task() to make it part of the new helpers.

This will allow us to enhance FSGSBASE support and eventually enable
the FSBASE/GSBASE instructions.

An "inactive" GS base refers to a base saved at kernel entry
and being part of an inactive, non-running/stopped user-task.
(The typical ptrace model.)

Here are the new functions:

  x86_fsbase_read_task()
  x86_gsbase_read_task()
  x86_fsbase_write_task()
  x86_gsbase_write_task()
  x86_fsbase_read_cpu()
  x86_fsbase_write_cpu()
  x86_gsbase_read_cpu_inactive()
  x86_gsbase_write_cpu_inactive()

As an advantage of the unified namespace we can now see all FS/GSBASE
API use in the kernel via the following 'git grep' pattern:

  $ git grep x86_.*sbase

[ mingo: Wrote new changelog. ]

Based-on-code-from: Andy Lutomirski <luto@kernel.org>
Suggested-by: Ingo Molnar <mingo@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/1537312139-5580-3-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 16:08:53 -07:00
committed by Ingo Molnar
parent 07e1d88ada
commit b1378a561f
3 changed files with 179 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
arch/x86/kernel/ptrace.c
View File

@@ -39,7 +39,7 @@
#include <asm/hw_breakpoint.h>
#include <asm/traps.h>
#include <asm/syscall.h>
#include <asm/mmu_context.h>
#include <asm/fsgsbase.h>
#include "tls.h"
@@ -343,49 +343,6 @@ static int set_segment_reg(struct task_struct *task,
return 0;
}
static unsigned long task_seg_base(struct task_struct *task,
unsigned short selector)
{
unsigned short idx = selector >> 3;
unsigned long base;
if (likely((selector & SEGMENT_TI_MASK) == 0)) {
if (unlikely(idx >= GDT_ENTRIES))
return 0;
/*
* There are no user segments in the GDT with nonzero bases
* other than the TLS segments.
*/
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return 0;
idx -= GDT_ENTRY_TLS_MIN;
base = get_desc_base(&task->thread.tls_array[idx]);
} else {
#ifdef CONFIG_MODIFY_LDT_SYSCALL
struct ldt_struct *ldt;
/*
* If performance here mattered, we could protect the LDT
* with RCU. This is a slow path, though, so we can just
* take the mutex.
*/
mutex_lock(&task->mm->context.lock);
ldt = task->mm->context.ldt;
if (unlikely(idx >= ldt->nr_entries))
base = 0;
else
base = get_desc_base(ldt->entries + idx);
mutex_unlock(&task->mm->context.lock);
#else
base = 0;
#endif
}
return base;
}
#endif /* CONFIG_X86_32 */
static unsigned long get_flags(struct task_struct *task)
@@ -482,13 +439,15 @@ static unsigned long getreg(struct task_struct *task, unsigned long offset)
if (task->thread.fsindex == 0)
return task->thread.fsbase;
else
return task_seg_base(task, task->thread.fsindex);
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 task_seg_base(task, task->thread.gsindex);
return x86_fsgsbase_read_task(task,
task->thread.gsindex);
}
#endif
}