From ada857082317e6883cfcf7deb4e0c54d3c447cb0 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 25 Jun 2008 00:19:00 -0400 Subject: [PATCH] x86: remove open-coded save/load segment operations This removes a pile of buggy open-coded implementations of savesegment and loadsegment. (They are buggy because they don't have memory barriers to prevent them from being reordered with respect to memory accesses.) Signed-off-by: Jeremy Fitzhardinge Cc: xen-devel Cc: Stephen Tweedie Cc: Eduardo Habkost Cc: Mark McLoughlin Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/common_64.c | 3 ++- arch/x86/kernel/process_64.c | 28 +++++++++++++++------------- 2 files changed, 17 insertions(+), 14 deletions(-) diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c index 39eaefbcec..7518502352 100644 --- a/arch/x86/kernel/cpu/common_64.c +++ b/arch/x86/kernel/cpu/common_64.c @@ -480,7 +480,8 @@ void pda_init(int cpu) struct x8664_pda *pda = cpu_pda(cpu); /* Setup up data that may be needed in __get_free_pages early */ - asm volatile("movl %0,%%fs ; movl %0,%%gs" :: "r" (0)); + loadsegment(fs, 0); + loadsegment(gs, 0); /* Memory clobbers used to order PDA accessed */ mb(); wrmsrl(MSR_GS_BASE, pda); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 290183e973..ddc6fcc73d 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -335,10 +335,10 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long sp, p->thread.fs = me->thread.fs; p->thread.gs = me->thread.gs; - asm("mov %%gs,%0" : "=m" (p->thread.gsindex)); - asm("mov %%fs,%0" : "=m" (p->thread.fsindex)); - asm("mov %%es,%0" : "=m" (p->thread.es)); - asm("mov %%ds,%0" : "=m" (p->thread.ds)); + savesegment(gs, p->thread.gsindex); + savesegment(fs, p->thread.fsindex); + savesegment(es, p->thread.es); + savesegment(ds, p->thread.ds); if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) { p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); @@ -377,7 +377,9 @@ out: void start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) { - asm volatile("movl %0, %%fs; movl %0, %%es; movl %0, %%ds" :: "r"(0)); + loadsegment(fs, 0); + loadsegment(es, 0); + loadsegment(ds, 0); load_gs_index(0); regs->ip = new_ip; regs->sp = new_sp; @@ -550,11 +552,11 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) * Switch DS and ES. * This won't pick up thread selector changes, but I guess that is ok. */ - asm volatile("mov %%es,%0" : "=m" (prev->es)); + savesegment(es, prev->es); if (unlikely(next->es | prev->es)) loadsegment(es, next->es); - - asm volatile ("mov %%ds,%0" : "=m" (prev->ds)); + + savesegment(ds, prev->ds); if (unlikely(next->ds | prev->ds)) loadsegment(ds, next->ds); @@ -565,7 +567,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) */ { unsigned fsindex; - asm volatile("movl %%fs,%0" : "=r" (fsindex)); + savesegment(fs, fsindex); /* segment register != 0 always requires a reload. also reload when it has changed. when prev process used 64bit base always reload @@ -586,7 +588,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) } { unsigned gsindex; - asm volatile("movl %%gs,%0" : "=r" (gsindex)); + savesegment(gs, gsindex); if (unlikely(gsindex | next->gsindex | prev->gs)) { load_gs_index(next->gsindex); if (gsindex) @@ -767,7 +769,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr) set_32bit_tls(task, FS_TLS, addr); if (doit) { load_TLS(&task->thread, cpu); - asm volatile("movl %0,%%fs" :: "r"(FS_TLS_SEL)); + loadsegment(fs, FS_TLS_SEL); } task->thread.fsindex = FS_TLS_SEL; task->thread.fs = 0; @@ -777,7 +779,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr) if (doit) { /* set the selector to 0 to not confuse __switch_to */ - asm volatile("movl %0,%%fs" :: "r" (0)); + loadsegment(fs, 0); ret = checking_wrmsrl(MSR_FS_BASE, addr); } } @@ -800,7 +802,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr) if (task->thread.gsindex == GS_TLS_SEL) base = read_32bit_tls(task, GS_TLS); else if (doit) { - asm("movl %%gs,%0" : "=r" (gsindex)); + savesegment(gs, gsindex); if (gsindex) rdmsrl(MSR_KERNEL_GS_BASE, base); else -- 2.39.5