[patch V2 07/16] x86/ioperm: Move iobitmap data into a struct
From: Thomas Gleixner
Date: Mon Nov 11 2019 - 17:35:51 EST
No point in having all the data in thread_struct, especially as upcoming
changes add more.
Make the bitmap in the new struct accessible as array of longs and as array
of characters via a union, so both the bitmap functions and the update
logic can avoid type casts.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
V2: New patch
---
arch/x86/include/asm/iobitmap.h | 15 ++++++++
arch/x86/include/asm/processor.h | 21 +++++------
arch/x86/kernel/cpu/common.c | 2 -
arch/x86/kernel/ioport.c | 69 +++++++++++++++++++--------------------
arch/x86/kernel/process.c | 38 +++++++++++----------
arch/x86/kernel/ptrace.c | 12 ++++--
6 files changed, 89 insertions(+), 68 deletions(-)
--- /dev/null
+++ b/arch/x86/include/asm/iobitmap.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_IOBITMAP_H
+#define _ASM_X86_IOBITMAP_H
+
+#include <asm/processor.h>
+
+struct io_bitmap {
+ unsigned int io_bitmap_max;
+ union {
+ unsigned long bits[IO_BITMAP_LONGS];
+ unsigned char bitmap_bytes[IO_BITMAP_BYTES];
+ };
+};
+
+#endif
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -7,6 +7,7 @@
/* Forward declaration, a strange C thing */
struct task_struct;
struct mm_struct;
+struct io_bitmap;
struct vm86;
#include <asm/math_emu.h>
@@ -328,22 +329,22 @@ struct x86_hw_tss {
* IO-bitmap sizes:
*/
#define IO_BITMAP_BITS 65536
-#define IO_BITMAP_BYTES (IO_BITMAP_BITS/8)
-#define IO_BITMAP_LONGS (IO_BITMAP_BYTES/sizeof(long))
+#define IO_BITMAP_BYTES (IO_BITMAP_BITS / BITS_PER_BYTE)
+#define IO_BITMAP_LONGS (IO_BITMAP_BYTES / sizeof(long))
#define IO_BITMAP_OFFSET_VALID \
- (offsetof(struct tss_struct, io_bitmap) - \
+ (offsetof(struct tss_struct, io_bitmap_bytes) - \
offsetof(struct tss_struct, x86_tss))
/*
- * sizeof(unsigned long) coming from an extra "long" at the end
- * of the iobitmap.
+ * The extra byte at the end is required by the hardware. It has all
+ * bits set.
*
* -1? seg base+limit should be pointing to the address of the
* last valid byte
*/
#define __KERNEL_TSS_LIMIT \
- (IO_BITMAP_OFFSET_VALID + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
+ (IO_BITMAP_OFFSET_VALID + IO_BITMAP_BYTES + 1 - 1)
/* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
#define IO_BITMAP_OFFSET_INVALID (__KERNEL_TSS_LIMIT + 1)
@@ -379,7 +380,8 @@ struct tss_struct {
* bitmap. The extra byte must be all 1 bits, and must
* be within the limit.
*/
- unsigned long io_bitmap[IO_BITMAP_LONGS + 1];
+ unsigned char io_bitmap_bytes[IO_BITMAP_BYTES + 1]
+ __aligned(sizeof(unsigned long));
} __aligned(PAGE_SIZE);
DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
@@ -494,10 +496,8 @@ struct thread_struct {
struct vm86 *vm86;
#endif
/* IO permissions: */
- unsigned long *io_bitmap_ptr;
+ struct io_bitmap *io_bitmap;
unsigned long iopl;
- /* Max allowed port in the bitmap, in bytes: */
- unsigned io_bitmap_max;
mm_segment_t addr_limit;
@@ -855,7 +855,6 @@ static inline void spin_lock_prefetch(co
#define INIT_THREAD { \
.sp0 = TOP_OF_INIT_STACK, \
.sysenter_cs = __KERNEL_CS, \
- .io_bitmap_ptr = NULL, \
.addr_limit = KERNEL_DS, \
}
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1862,7 +1862,7 @@ void cpu_init(void)
tss_setup_ist(tss);
tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
tss->io_bitmap_prev_max = 0;
- memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
+ memset(tss->io_bitmap_bytes, 0xff, sizeof(tss->io_bitmap_bytes));
set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
load_TR_desc();
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -11,6 +11,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
+#include <asm/iobitmap.h>
#include <asm/desc.h>
/*
@@ -18,9 +19,10 @@
*/
long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
{
+ unsigned int i, max_long, bytes, bytes_updated;
struct thread_struct *t = ¤t->thread;
struct tss_struct *tss;
- unsigned int i, max_long, bytes, bytes_updated;
+ struct io_bitmap *iobm;
if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
return -EINVAL;
@@ -33,62 +35,61 @@ long ksys_ioperm(unsigned long from, uns
* IO bitmap up. ioperm() is much less timing critical than clone(),
* this is why we delay this operation until now:
*/
- if (!t->io_bitmap_ptr) {
- unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
+ iobm = t->io_bitmap;
- if (!bitmap)
- return -ENOMEM;
+ if (!iobm) {
+ if (!turn_on)
+ return 0;
- memset(bitmap, 0xff, IO_BITMAP_BYTES);
+ iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
+ if (!iobm)
+ return -ENOMEM;
- /*
- * Now that we have an IO bitmap, we need our TSS limit to be
- * correct. It's fine if we are preempted after doing this:
- * with TIF_IO_BITMAP set, context switches will keep our TSS
- * limit correct.
- */
- preempt_disable();
- t->io_bitmap_ptr = bitmap;
- set_thread_flag(TIF_IO_BITMAP);
- /* Make the bitmap base in the TSS valid */
- tss = this_cpu_ptr(&cpu_tss_rw);
- tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
- refresh_tss_limit();
- preempt_enable();
+ memset(iobm->bits, 0xff, sizeof(iobm->bits));
}
/*
- * do it in the per-thread copy and in the TSS ...
- *
- * Disable preemption via get_cpu() - we must not switch away
- * because the ->io_bitmap_max value must match the bitmap
- * contents:
+ * Update the tasks bitmap and the TSS copy. This requires to have
+ * preemption disabled to protect against a context switch.
*/
- tss = &per_cpu(cpu_tss_rw, get_cpu());
+ preempt_disable();
+ tss = this_cpu_ptr(&cpu_tss_rw);
+ /* Update the bitmap */
if (turn_on)
- bitmap_clear(t->io_bitmap_ptr, from, num);
+ bitmap_clear(iobm->bits, from, num);
else
- bitmap_set(t->io_bitmap_ptr, from, num);
+ bitmap_set(iobm->bits, from, num);
/*
* Search for a (possibly new) maximum. This is simple and stupid,
* to keep it obviously correct:
*/
max_long = 0;
- for (i = 0; i < IO_BITMAP_LONGS; i++)
- if (t->io_bitmap_ptr[i] != ~0UL)
+ for (i = 0; i < IO_BITMAP_LONGS; i++) {
+ if (iobm->bits[i] != ~0UL)
max_long = i;
+ }
bytes = (max_long + 1) * sizeof(unsigned long);
- bytes_updated = max(bytes, t->io_bitmap_max);
+ bytes_updated = max(bytes, iobm->io_bitmap_max);
- t->io_bitmap_max = bytes;
+ iobm->io_bitmap_max = bytes;
/* Update the TSS: */
- memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+ memcpy(tss->io_bitmap_bytes, iobm->bitmap_bytes, bytes_updated);
- put_cpu();
+ /* Set the tasks io_bitmap pointer (might be the same) */
+ t->io_bitmap = iobm;
+ /* Mark it active for context switching */
+ set_thread_flag(TIF_IO_BITMAP);
+
+ /* Make the bitmap base in the TSS valid */
+ tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
+
+ /* Make sure the TSS limit covers the I/O bitmap. */
+ refresh_tss_limit();
+ preempt_enable();
return 0;
}
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -41,6 +41,7 @@
#include <asm/desc.h>
#include <asm/prctl.h>
#include <asm/spec-ctrl.h>
+#include <asm/iobitmap.h>
#include <asm/proto.h>
#include "process.h"
@@ -101,21 +102,20 @@ int arch_dup_task_struct(struct task_str
void exit_thread(struct task_struct *tsk)
{
struct thread_struct *t = &tsk->thread;
- unsigned long *bp = t->io_bitmap_ptr;
+ struct io_bitmap *bm = t->io_bitmap;
struct fpu *fpu = &t->fpu;
struct tss_struct *tss;
- if (bp) {
+ if (bm) {
preempt_disable();
tss = this_cpu_ptr(&cpu_tss_rw);
- t->io_bitmap_ptr = NULL;
- t->io_bitmap_max = 0;
+ t->io_bitmap = NULL;
clear_thread_flag(TIF_IO_BITMAP);
/* Invalidate the io bitmap base in the TSS */
tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
preempt_enable();
- kfree(bp);
+ kfree(bm);
}
free_vm86(t);
@@ -135,25 +135,25 @@ static int set_new_tls(struct task_struc
static inline int copy_io_bitmap(struct task_struct *tsk)
{
+ struct io_bitmap *bm = current->thread.io_bitmap;
+
if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
return 0;
- tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
- IO_BITMAP_BYTES, GFP_KERNEL);
- if (!tsk->thread.io_bitmap_ptr) {
- tsk->thread.io_bitmap_max = 0;
+ tsk->thread.io_bitmap = kmemdup(bm, sizeof(*bm), GFP_KERNEL);
+
+ if (!tsk->thread.io_bitmap)
return -ENOMEM;
- }
+
set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
return 0;
}
static inline void free_io_bitmap(struct task_struct *tsk)
{
- if (tsk->thread.io_bitmap_ptr) {
- kfree(tsk->thread.io_bitmap_ptr);
- tsk->thread.io_bitmap_ptr = NULL;
- tsk->thread.io_bitmap_max = 0;
+ if (tsk->thread.io_bitmap) {
+ kfree(tsk->thread.io_bitmap);
+ tsk->thread.io_bitmap = NULL;
}
}
@@ -172,7 +172,7 @@ int copy_thread_tls(unsigned long clone_
frame->bp = 0;
frame->ret_addr = (unsigned long) ret_from_fork;
p->thread.sp = (unsigned long) fork_frame;
- p->thread.io_bitmap_ptr = NULL;
+ p->thread.io_bitmap = NULL;
memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
#ifdef CONFIG_X86_64
@@ -360,6 +360,8 @@ static inline void switch_to_bitmap(stru
struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
if (tifn & _TIF_IO_BITMAP) {
+ struct io_bitmap *iobm = next->io_bitmap;
+
/*
* Copy at least the size of the incoming tasks bitmap
* which covers the last permitted I/O port.
@@ -368,11 +370,11 @@ static inline void switch_to_bitmap(stru
* bits permitted, then the copy needs to cover those as
* well so they get turned off.
*/
- memcpy(tss->io_bitmap, next->io_bitmap_ptr,
- max(tss->io_bitmap_prev_max, next->io_bitmap_max));
+ memcpy(tss->io_bitmap_bytes, iobm->bitmap_bytes,
+ max(tss->io_bitmap_prev_max, iobm->io_bitmap_max));
/* Store the new max and set io_bitmap_base valid */
- tss->io_bitmap_prev_max = next->io_bitmap_max;
+ tss->io_bitmap_prev_max = iobm->io_bitmap_max;
tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
/*
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -42,6 +42,7 @@
#include <asm/traps.h>
#include <asm/syscall.h>
#include <asm/fsgsbase.h>
+#include <asm/iobitmap.h>
#include "tls.h"
@@ -697,7 +698,9 @@ static int ptrace_set_debugreg(struct ta
static int ioperm_active(struct task_struct *target,
const struct user_regset *regset)
{
- return DIV_ROUND_UP(target->thread.io_bitmap_max, regset->size);
+ struct io_bitmap *iobm = target->thread.io_bitmap;
+
+ return iobm ? DIV_ROUND_UP(iobm->io_bitmap_max, regset->size) : 0;
}
static int ioperm_get(struct task_struct *target,
@@ -705,12 +708,13 @@ static int ioperm_get(struct task_struct
unsigned int pos, unsigned int count,
void *kbuf, void __user *ubuf)
{
- if (!target->thread.io_bitmap_ptr)
+ struct io_bitmap *iobm = target->thread.io_bitmap;
+
+ if (!iobm)
return -ENXIO;
return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
- target->thread.io_bitmap_ptr,
- 0, IO_BITMAP_BYTES);
+ iobm->bitmap_bytes, 0, IO_BITMAP_BYTES);
}
/*