Commit 6a3713f0 authored by Brian Gerst's avatar Brian Gerst Committed by Ingo Molnar
Browse files

x86/signal: Remove pax argument from restore_sigcontext 

The 'pax' argument is unnecesary.  Instead, store the RAX value
directly in regs.

This pattern goes all the way back to 2.1.106pre1, when restore_sigcontext()
was changed to return an error code instead of EAX directly:

  https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174



In 2007 sigaltstack syscall support was added, where the return
value of restore_sigcontext() was changed to carry the memory-copying
failure code.

But instead of putting 'ax' into regs->ax directly, it was carried
in via a pointer and then returned, where the generic syscall return
code copied it to regs->ax.

So there was never any deeper reason for this suboptimal pattern, it
was simply never noticed after being introduced.

Signed-off-by: default avatarBrian Gerst <brgerst@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1428152303-17154-1-git-send-email-brgerst@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent dbe4058a

arch/x86/ia32/ia32_signal.c

+6 −11
Original line number Diff line number Diff line
@@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from) 
}



static int ia32_restore_sigcontext(struct pt_regs *regs,

				   struct sigcontext_ia32 __user *sc,

				   unsigned int *pax)

				   struct sigcontext_ia32 __user *sc)

{

	unsigned int tmpflags, err = 0;

	void __user *buf;
@@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs, 
		RELOAD_SEG(es);



		COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);

		COPY(dx); COPY(cx); COPY(ip);

		COPY(dx); COPY(cx); COPY(ip); COPY(ax);

		/* Don't touch extended registers */



		COPY_SEG_CPL3(cs);
@@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs, 


		get_user_ex(tmp, &sc->fpstate);

		buf = compat_ptr(tmp);



		get_user_ex(*pax, &sc->ax);

	} get_user_catch(err);



	err |= restore_xstate_sig(buf, 1);
@@ -213,7 +210,6 @@ asmlinkage long sys32_sigreturn(void) 
	struct pt_regs *regs = current_pt_regs();

	struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);

	sigset_t set;

	unsigned int ax;



	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))

		goto badframe;
@@ -226,9 +222,9 @@ asmlinkage long sys32_sigreturn(void) 


	set_current_blocked(&set);



	if (ia32_restore_sigcontext(regs, &frame->sc, &ax))

	if (ia32_restore_sigcontext(regs, &frame->sc))

		goto badframe;

	return ax;

	return regs->ax;



badframe:

	signal_fault(regs, frame, "32bit sigreturn");
@@ -240,7 +236,6 @@ asmlinkage long sys32_rt_sigreturn(void) 
	struct pt_regs *regs = current_pt_regs();

	struct rt_sigframe_ia32 __user *frame;

	sigset_t set;

	unsigned int ax;



	frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
@@ -251,13 +246,13 @@ asmlinkage long sys32_rt_sigreturn(void) 


	set_current_blocked(&set);



	if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))

	if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))

		goto badframe;



	if (compat_restore_altstack(&frame->uc.uc_stack))

		goto badframe;



	return ax;

	return regs->ax;



badframe:

	signal_fault(regs, frame, "32bit rt sigreturn");

arch/x86/include/asm/sighandling.h

+1 −3
Original line number Diff line number Diff line
@@ -13,9 +13,7 @@ 
			 X86_EFLAGS_CF | X86_EFLAGS_RF)



void signal_fault(struct pt_regs *regs, void __user *frame, char *where);



int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,

		       unsigned long *pax);

int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc);

int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,

		     struct pt_regs *regs, unsigned long mask);

arch/x86/kernel/signal.c

+8 −14
Original line number Diff line number Diff line
@@ -61,8 +61,7 @@ 
	regs->seg = GET_SEG(seg) | 3;			\

} while (0)



int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,

		       unsigned long *pax)

int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)

{

	void __user *buf;

	unsigned int tmpflags;
@@ -81,7 +80,7 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, 
#endif /* CONFIG_X86_32 */



		COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);

		COPY(dx); COPY(cx); COPY(ip);

		COPY(dx); COPY(cx); COPY(ip); COPY(ax);



#ifdef CONFIG_X86_64

		COPY(r8);
@@ -102,8 +101,6 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, 
		regs->orig_ax = -1;		/* disable syscall checks */



		get_user_ex(buf, &sc->fpstate);



		get_user_ex(*pax, &sc->ax);

	} get_user_catch(err);



	err |= restore_xstate_sig(buf, config_enabled(CONFIG_X86_32));
@@ -545,7 +542,6 @@ asmlinkage unsigned long sys_sigreturn(void) 
{

	struct pt_regs *regs = current_pt_regs();

	struct sigframe __user *frame;

	unsigned long ax;

	sigset_t set;



	frame = (struct sigframe __user *)(regs->sp - 8);
@@ -559,9 +555,9 @@ asmlinkage unsigned long sys_sigreturn(void) 


	set_current_blocked(&set);



	if (restore_sigcontext(regs, &frame->sc, &ax))

	if (restore_sigcontext(regs, &frame->sc))

		goto badframe;

	return ax;

	return regs->ax;



badframe:

	signal_fault(regs, frame, "sigreturn");
@@ -574,7 +570,6 @@ asmlinkage long sys_rt_sigreturn(void) 
{

	struct pt_regs *regs = current_pt_regs();

	struct rt_sigframe __user *frame;

	unsigned long ax;

	sigset_t set;



	frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
@@ -585,13 +580,13 @@ asmlinkage long sys_rt_sigreturn(void) 


	set_current_blocked(&set);



	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))

	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))

		goto badframe;



	if (restore_altstack(&frame->uc.uc_stack))

		goto badframe;



	return ax;

	return regs->ax;



badframe:

	signal_fault(regs, frame, "rt_sigreturn");
@@ -786,7 +781,6 @@ asmlinkage long sys32_x32_rt_sigreturn(void) 
	struct pt_regs *regs = current_pt_regs();

	struct rt_sigframe_x32 __user *frame;

	sigset_t set;

	unsigned long ax;



	frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
@@ -797,13 +791,13 @@ asmlinkage long sys32_x32_rt_sigreturn(void) 


	set_current_blocked(&set);



	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))

	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))

		goto badframe;



	if (compat_restore_altstack(&frame->uc.uc_stack))

		goto badframe;



	return ax;

	return regs->ax;



badframe:

	signal_fault(regs, frame, "x32 rt_sigreturn");

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