Save %gs in sigcontext when delivering a signal and restore them upon

return (in signal trampoline code). I plan to do the same on -stable,
so that we have a consistent interface to userland applications.

Reviewed by:	bde

sys/amd64/amd64/genassym.c

@@ -148,6 +148,9 @@ main()
 
 	printf("#define\tSIGF_HANDLER %#x\n", OS(sigframe, sf_ahu.sf_handler));
 	printf("#define\tSIGF_SC %#x\n", OS(sigframe, sf_siginfo.si_sc));
+	printf("#define\tSC_PS %#x\n", OS(sigcontext, sc_ps));
+	printf("#define\tSC_FS %#x\n", OS(sigcontext, sc_fs));
+	printf("#define\tSC_GS %#x\n", OS(sigcontext, sc_gs));
 
 	printf("#define\tB_READ %#x\n", B_READ);
 	printf("#define\tENOENT %d\n", ENOENT);

sys/amd64/amd64/locore.S

@@ -410,8 +410,6 @@ NON_GPROF_ENTRY(prepare_usermode)
 	ret					/* goto user! */
 
 
-#define LCALL(x,y)	.byte 0x9a ; .long y ; .word x
-
 /*
  * Signal trampoline, copied to top of user stack
  */
@@ -421,9 +419,13 @@ NON_GPROF_ENTRY(sigcode)
 						/* copy at 8(%esp)) */
 	pushl	%eax
 	pushl	%eax				/* junk to fake return address */
+	testl	$PSL_VM,SC_PS(%eax)
+	jne	1f
+	movl	SC_GS(%eax),%gs			/* restore %gs */
+1:
 	movl	$SYS_sigreturn,%eax		/* sigreturn() */
-	LCALL(0x7,0)				/* enter kernel with args on stack */
+	int	$0x80				/* enter kernel with args on stack */
-	hlt					/* never gets here */
+2:	jmp	2b
 	ALIGN_TEXT
 _esigcode:
 

sys/amd64/amd64/locore.s

@@ -410,8 +410,6 @@ NON_GPROF_ENTRY(prepare_usermode)
 	ret					/* goto user! */
 
 
-#define LCALL(x,y)	.byte 0x9a ; .long y ; .word x
-
 /*
  * Signal trampoline, copied to top of user stack
  */
@@ -421,9 +419,13 @@ NON_GPROF_ENTRY(sigcode)
 						/* copy at 8(%esp)) */
 	pushl	%eax
 	pushl	%eax				/* junk to fake return address */
+	testl	$PSL_VM,SC_PS(%eax)
+	jne	1f
+	movl	SC_GS(%eax),%gs			/* restore %gs */
+1:
 	movl	$SYS_sigreturn,%eax		/* sigreturn() */
-	LCALL(0x7,0)				/* enter kernel with args on stack */
+	int	$0x80				/* enter kernel with args on stack */
-	hlt					/* never gets here */
+2:	jmp	2b
 	ALIGN_TEXT
 _esigcode:
 

sys/amd64/amd64/machdep.c

@@ -562,6 +562,7 @@ sendsig(catcher, sig, mask, code)
 	sf.sf_siginfo.si_sc.sc_ss = regs->tf_ss;
 	sf.sf_siginfo.si_sc.sc_es = regs->tf_es;
 	sf.sf_siginfo.si_sc.sc_fs = regs->tf_fs;
+	sf.sf_siginfo.si_sc.sc_gs = rgs();
 	sf.sf_siginfo.si_sc.sc_isp = regs->tf_isp;
 
 	/*

sys/i386/i386/genassym.c

@@ -148,6 +148,9 @@ main()
 
 	printf("#define\tSIGF_HANDLER %#x\n", OS(sigframe, sf_ahu.sf_handler));
 	printf("#define\tSIGF_SC %#x\n", OS(sigframe, sf_siginfo.si_sc));
+	printf("#define\tSC_PS %#x\n", OS(sigcontext, sc_ps));
+	printf("#define\tSC_FS %#x\n", OS(sigcontext, sc_fs));
+	printf("#define\tSC_GS %#x\n", OS(sigcontext, sc_gs));
 
 	printf("#define\tB_READ %#x\n", B_READ);
 	printf("#define\tENOENT %d\n", ENOENT);

sys/i386/i386/locore.s

@@ -410,8 +410,6 @@ NON_GPROF_ENTRY(prepare_usermode)
 	ret					/* goto user! */
 
 
-#define LCALL(x,y)	.byte 0x9a ; .long y ; .word x
-
 /*
  * Signal trampoline, copied to top of user stack
  */
@@ -421,9 +419,13 @@ NON_GPROF_ENTRY(sigcode)
 						/* copy at 8(%esp)) */
 	pushl	%eax
 	pushl	%eax				/* junk to fake return address */
+	testl	$PSL_VM,SC_PS(%eax)
+	jne	1f
+	movl	SC_GS(%eax),%gs			/* restore %gs */
+1:
 	movl	$SYS_sigreturn,%eax		/* sigreturn() */
-	LCALL(0x7,0)				/* enter kernel with args on stack */
+	int	$0x80				/* enter kernel with args on stack */
-	hlt					/* never gets here */
+2:	jmp	2b
 	ALIGN_TEXT
 _esigcode:
 

sys/i386/i386/machdep.c

@@ -562,6 +562,7 @@ sendsig(catcher, sig, mask, code)
 	sf.sf_siginfo.si_sc.sc_ss = regs->tf_ss;
 	sf.sf_siginfo.si_sc.sc_es = regs->tf_es;
 	sf.sf_siginfo.si_sc.sc_fs = regs->tf_fs;
+	sf.sf_siginfo.si_sc.sc_gs = rgs();
 	sf.sf_siginfo.si_sc.sc_isp = regs->tf_isp;
 
 	/*