x86, xsave: dynamically allocate sigframes fpstate instead of static allocation
dynamically allocate fpstate on the stack, instead of static allocation
in the current sigframe layout on the user stack. This will allow the
fpstate structure to grow in the future, which includes extended state
information supporting xsave/xrstor.
signal handlers will be able to access the fpstate pointer from the
sigcontext structure asusual, with no change. For the non RT sigframe's
(which are supported only for 32bit apps), current static fpstate layout
in the sigframe will be unused(so that we don't change the extramask[]
offset in the sigframe and thus prevent breaking app's which modify
extramask[]).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index b778e17..51fb288 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -24,6 +24,7 @@
# define save_i387_ia32 save_i387
# define restore_i387_ia32 restore_i387
# define _fpstate_ia32 _fpstate
+# define sig_xstate_ia32_size sig_xstate_size
# define user_i387_ia32_struct user_i387_struct
# define user32_fxsr_struct user_fxsr_struct
#endif
@@ -36,6 +37,7 @@
static unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
unsigned int xstate_size;
+unsigned int sig_xstate_ia32_size = sizeof(struct _fpstate_ia32);
static struct i387_fxsave_struct fx_scratch __cpuinitdata;
void __cpuinit mxcsr_feature_mask_init(void)
diff --git a/arch/x86/kernel/sigframe.h b/arch/x86/kernel/sigframe.h
index 72bbb51..6dd7e2b 100644
--- a/arch/x86/kernel/sigframe.h
+++ b/arch/x86/kernel/sigframe.h
@@ -3,9 +3,18 @@
char __user *pretcode;
int sig;
struct sigcontext sc;
- struct _fpstate fpstate;
+ /*
+ * fpstate is unused. fpstate is moved/allocated after
+ * retcode[] below. This movement allows to have the FP state and the
+ * future state extensions (xsave) stay together.
+ * And at the same time retaining the unused fpstate, prevents changing
+ * the offset of extramask[] in the sigframe and thus prevent any
+ * legacy application accessing/modifying it.
+ */
+ struct _fpstate fpstate_unused;
unsigned long extramask[_NSIG_WORDS-1];
char retcode[8];
+ /* fp state follows here */
};
struct rt_sigframe {
@@ -15,13 +24,14 @@
void __user *puc;
struct siginfo info;
struct ucontext uc;
- struct _fpstate fpstate;
char retcode[8];
+ /* fp state follows here */
};
#else
struct rt_sigframe {
char __user *pretcode;
struct ucontext uc;
struct siginfo info;
+ /* fp state follows here */
};
#endif
diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c
index 6fb5bcd..19a7a56 100644
--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -306,7 +306,8 @@
* Determine which stack to use..
*/
static inline void __user *
-get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
+get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
+ struct _fpstate **fpstate)
{
unsigned long sp;
@@ -332,6 +333,11 @@
sp = (unsigned long) ka->sa.sa_restorer;
}
+ if (used_math()) {
+ sp = sp - sig_xstate_size;
+ *fpstate = (struct _fpstate *) sp;
+ }
+
sp -= frame_size;
/*
* Align the stack pointer according to the i386 ABI,
@@ -350,8 +356,9 @@
void __user *restorer;
int err = 0;
int usig;
+ struct _fpstate __user *fpstate = NULL;
- frame = get_sigframe(ka, regs, sizeof(*frame));
+ frame = get_sigframe(ka, regs, sizeof(*frame), &fpstate);
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
@@ -366,7 +373,7 @@
if (err)
goto give_sigsegv;
- err = setup_sigcontext(&frame->sc, &frame->fpstate, regs, set->sig[0]);
+ err = setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]);
if (err)
goto give_sigsegv;
@@ -427,8 +434,9 @@
void __user *restorer;
int err = 0;
int usig;
+ struct _fpstate __user *fpstate = NULL;
- frame = get_sigframe(ka, regs, sizeof(*frame));
+ frame = get_sigframe(ka, regs, sizeof(*frame), &fpstate);
if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
goto give_sigsegv;
@@ -453,7 +461,7 @@
err |= __put_user(sas_ss_flags(regs->sp),
&frame->uc.uc_stack.ss_flags);
err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
- err |= setup_sigcontext(&frame->uc.uc_mcontext, &frame->fpstate,
+ err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
regs, set->sig[0]);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
if (err)
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index ca316b5..0deab8e 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -281,7 +281,7 @@
struct task_struct *me = current;
if (used_math()) {
- fp = get_stack(ka, regs, sizeof(struct _fpstate));
+ fp = get_stack(ka, regs, sig_xstate_size);
frame = (void __user *)round_down(
(unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index c68b7c4..7ad169e 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -17,6 +17,10 @@
*/
struct xsave_struct *init_xstate_buf;
+#ifdef CONFIG_X86_64
+unsigned int sig_xstate_size = sizeof(struct _fpstate);
+#endif
+
/*
* Enable the extended processor state save/restore feature
*/
