[PATCH 6/8] x86/asm/64: Rename thread_struct's fs and gs to fsbase and gsbase
From: Andy Lutomirski
Date: Tue Apr 26 2016 - 15:24:36 EST
Unlike ds and es, these are base addresses, not selectors. Rename
them so their meaning is more obvious.
On x86_32, the field is still called fs. Fixing that could make sense
as a future cleanup.
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
arch/x86/include/asm/elf.h | 6 +++---
arch/x86/include/asm/processor.h | 11 +++++++++--
arch/x86/kernel/process_64.c | 30 +++++++++++++++---------------
arch/x86/kernel/ptrace.c | 8 ++++----
arch/x86/kvm/svm.c | 2 +-
5 files changed, 32 insertions(+), 25 deletions(-)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 15340e36ddcb..fea7724141a0 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -176,7 +176,7 @@ static inline void elf_common_init(struct thread_struct *t,
regs->si = regs->di = regs->bp = 0;
regs->r8 = regs->r9 = regs->r10 = regs->r11 = 0;
regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
- t->fs = t->gs = 0;
+ t->fsbase = t->gsbase = 0;
t->fsindex = t->gsindex = 0;
t->ds = t->es = ds;
}
@@ -226,8 +226,8 @@ do { \
(pr_reg)[18] = (regs)->flags; \
(pr_reg)[19] = (regs)->sp; \
(pr_reg)[20] = (regs)->ss; \
- (pr_reg)[21] = current->thread.fs; \
- (pr_reg)[22] = current->thread.gs; \
+ (pr_reg)[21] = current->thread.fsbase; \
+ (pr_reg)[22] = current->thread.gsbase; \
asm("movl %%ds,%0" : "=r" (v)); (pr_reg)[23] = v; \
asm("movl %%es,%0" : "=r" (v)); (pr_reg)[24] = v; \
asm("movl %%fs,%0" : "=r" (v)); (pr_reg)[25] = v; \
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 9264476f3d57..9251aa962721 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -388,9 +388,16 @@ struct thread_struct {
unsigned long ip;
#endif
#ifdef CONFIG_X86_64
- unsigned long fs;
+ unsigned long fsbase;
+ unsigned long gsbase;
+#else
+ /*
+ * XXX: this could presumably be unsigned short. Alternatively,
+ * 32-bit kernels could be taught to use fsindex instead.
+ */
+ unsigned long fs;
+ unsigned long gs;
#endif
- unsigned long gs;
/* Save middle states of ptrace breakpoints */
struct perf_event *ptrace_bps[HBP_NUM];
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 556a19672ea2..ac78ec2f2d77 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -150,9 +150,9 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
p->thread.io_bitmap_ptr = NULL;
savesegment(gs, p->thread.gsindex);
- p->thread.gs = p->thread.gsindex ? 0 : me->thread.gs;
+ p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase;
savesegment(fs, p->thread.fsindex);
- p->thread.fs = p->thread.fsindex ? 0 : me->thread.fs;
+ p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase;
savesegment(es, p->thread.es);
savesegment(ds, p->thread.ds);
memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
@@ -329,18 +329,18 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* stronger guarantees.)
*
* As an invariant,
- * (fs != 0 && fsindex != 0) || (gs != 0 && gsindex != 0) is
+ * (fsbase != 0 && fsindex != 0) || (gsbase != 0 && gsindex != 0) is
* impossible.
*/
if (next->fsindex) {
/* Loading a nonzero value into FS sets the index and base. */
loadsegment(fs, next->fsindex);
} else {
- if (next->fs) {
+ if (next->fsbase) {
/* Next index is zero but next base is nonzero. */
if (prev_fsindex)
loadsegment(fs, 0);
- wrmsrl(MSR_FS_BASE, next->fs);
+ wrmsrl(MSR_FS_BASE, next->fsbase);
} else {
/* Next base and index are both zero. */
if (static_cpu_has_bug(X86_BUG_NULL_SEG)) {
@@ -356,7 +356,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* didn't change the base, then the base is
* also zero and we don't need to do anything.
*/
- if (prev->fs || prev_fsindex)
+ if (prev->fsbase || prev_fsindex)
loadsegment(fs, 0);
}
}
@@ -369,18 +369,18 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* us.
*/
if (prev_fsindex)
- prev->fs = 0;
+ prev->fsbase = 0;
prev->fsindex = prev_fsindex;
if (next->gsindex) {
/* Loading a nonzero value into GS sets the index and base. */
load_gs_index(next->gsindex);
} else {
- if (next->gs) {
+ if (next->gsbase) {
/* Next index is zero but next base is nonzero. */
if (prev_gsindex)
load_gs_index(0);
- wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
+ wrmsrl(MSR_KERNEL_GS_BASE, next->gsbase);
} else {
/* Next base and index are both zero. */
if (static_cpu_has_bug(X86_BUG_NULL_SEG)) {
@@ -400,7 +400,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* didn't change the base, then the base is
* also zero and we don't need to do anything.
*/
- if (prev->gs || prev_gsindex)
+ if (prev->gsbase || prev_gsindex)
load_gs_index(0);
}
}
@@ -413,7 +413,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* us.
*/
if (prev_gsindex)
- prev->gs = 0;
+ prev->gsbase = 0;
prev->gsindex = prev_gsindex;
switch_fpu_finish(next_fpu, fpu_switch);
@@ -536,7 +536,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
return -EPERM;
cpu = get_cpu();
task->thread.gsindex = 0;
- task->thread.gs = addr;
+ task->thread.gsbase = addr;
if (doit) {
load_gs_index(0);
ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, addr);
@@ -549,7 +549,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
return -EPERM;
cpu = get_cpu();
task->thread.fsindex = 0;
- task->thread.fs = addr;
+ task->thread.fsbase = addr;
if (doit) {
/* set the selector to 0 to not confuse __switch_to */
loadsegment(fs, 0);
@@ -562,7 +562,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
if (doit)
rdmsrl(MSR_FS_BASE, base);
else
- base = task->thread.fs;
+ base = task->thread.fsbase;
ret = put_user(base, (unsigned long __user *)addr);
break;
}
@@ -571,7 +571,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
if (doit)
rdmsrl(MSR_KERNEL_GS_BASE, base);
else
- base = task->thread.gs;
+ base = task->thread.gsbase;
ret = put_user(base, (unsigned long __user *)addr);
break;
}
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 8cbdd840a611..5d97d90aced3 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -399,7 +399,7 @@ static int putreg(struct task_struct *child,
* to set either thread.fs or thread.fsindex and the
* corresponding GDT slot.
*/
- if (child->thread.fs != value)
+ if (child->thread.fsbase != value)
return do_arch_prctl(child, ARCH_SET_FS, value);
return 0;
case offsetof(struct user_regs_struct,gs_base):
@@ -408,7 +408,7 @@ static int putreg(struct task_struct *child,
*/
if (value >= TASK_SIZE_OF(child))
return -EIO;
- if (child->thread.gs != value)
+ if (child->thread.gsbase != value)
return do_arch_prctl(child, ARCH_SET_GS, value);
return 0;
#endif
@@ -438,14 +438,14 @@ static unsigned long getreg(struct task_struct *task, unsigned long offset)
* XXX: This will not behave as expected if called on
* current or if fsindex != 0.
*/
- return task->thread.fs;
+ return task->thread.fsbase;
}
case offsetof(struct user_regs_struct, gs_base): {
/*
* XXX: This will not behave as expected if called on
* current or if fsindex != 0.
*/
- return task->thread.gs;
+ return task->thread.gsbase;
}
#endif
}
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 31346a3f20a5..fafd720ce10a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1254,7 +1254,7 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
kvm_load_ldt(svm->host.ldt);
#ifdef CONFIG_X86_64
loadsegment(fs, svm->host.fs);
- wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);
+ wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gsbase);
load_gs_index(svm->host.gs);
#else
#ifdef CONFIG_X86_32_LAZY_GS
--
2.5.5