Messages in this thread | | | Subject | Re: [Patch V2] x86/ldt: correct fpu emulation access to ldt | From | Juergen Gross <> | Date | Thu, 6 Aug 2015 11:13:16 +0200 |
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Please ignore, V3 coming soon.
Juergen
On 08/06/2015 11:07 AM, Juergen Gross wrote: > Commit 37868fe113ff ("x86/ldt: Make modify_ldt synchronous") introduced > a new struct ldt_struct anchored at mm->context.ldt. > > Adapt the x86 fpu emulation to use that new structure. > > Cc: <stable@vger.kernel.org> # 37868fe113ff: x86/ldt: Make modify_ldt synchronous > Cc: <stable@vger.kernel.org> # a5b9e5a2f14f: x86/ldt: Make modify_ldt optional > Signed-off-by: Juergen Gross <jgross@suse.com> > --- > arch/x86/math-emu/fpu_entry.c | 3 +-- > arch/x86/math-emu/fpu_system.h | 18 +++++++++++++++--- > arch/x86/math-emu/get_address.c | 3 +-- > 3 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c > index f37e84a..203318a 100644 > --- a/arch/x86/math-emu/fpu_entry.c > +++ b/arch/x86/math-emu/fpu_entry.c > @@ -29,7 +29,6 @@ > > #include <asm/uaccess.h> > #include <asm/traps.h> > -#include <asm/desc.h> > #include <asm/user.h> > #include <asm/fpu/internal.h> > > @@ -181,7 +180,7 @@ void math_emulate(struct math_emu_info *info) > math_abort(FPU_info, SIGILL); > } > > - code_descriptor = LDT_DESCRIPTOR(FPU_CS); > + code_descriptor = *FPU_get_ldt_descriptor(FPU_CS); > if (SEG_D_SIZE(code_descriptor)) { > /* The above test may be wrong, the book is not clear */ > /* Segmented 32 bit protected mode */ > diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h > index 9ccecb6..9330583 100644 > --- a/arch/x86/math-emu/fpu_system.h > +++ b/arch/x86/math-emu/fpu_system.h > @@ -16,9 +16,21 @@ > #include <linux/kernel.h> > #include <linux/mm.h> > > -/* s is always from a cpu register, and the cpu does bounds checking > - * during register load --> no further bounds checks needed */ > -#define LDT_DESCRIPTOR(s) (((struct desc_struct *)current->mm->context.ldt)[(s) >> 3]) > +#include <asm/desc.h> > +#include <asm/mmu_context.h> > + > +static inline struct desc_struct *FPU_get_ldt_descriptor(unsigned seg) > +{ > + static struct desc_struct zero_desc; > + > +#ifdef CONFIG_MODIFY_LDT_SYSCALL > + seg >>= 3; > + if (seg < current->mm->context.ldt->size) > + return current->mm->context.ldt->entries + seg; > +#endif > + return &zero_desc; > +} > + > #define SEG_D_SIZE(x) ((x).b & (3 << 21)) > #define SEG_G_BIT(x) ((x).b & (1 << 23)) > #define SEG_GRANULARITY(x) (((x).b & (1 << 23)) ? 4096 : 1) > diff --git a/arch/x86/math-emu/get_address.c b/arch/x86/math-emu/get_address.c > index 6ef5e99..f912edd 100644 > --- a/arch/x86/math-emu/get_address.c > +++ b/arch/x86/math-emu/get_address.c > @@ -20,7 +20,6 @@ > #include <linux/stddef.h> > > #include <asm/uaccess.h> > -#include <asm/desc.h> > > #include "fpu_system.h" > #include "exception.h" > @@ -158,7 +157,7 @@ static long pm_address(u_char FPU_modrm, u_char segment, > addr->selector = PM_REG_(segment); > } > > - descriptor = LDT_DESCRIPTOR(PM_REG_(segment)); > + descriptor = *FPU_get_ldt_descriptor(segment); > base_address = SEG_BASE_ADDR(descriptor); > address = base_address + offset; > limit = base_address >
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