OS-4201 need GS support in arch_prctl()

usr/src/uts/common/brand/lx/os/lx_brand.c

@@ -549,13 +549,16 @@ lx_restorecontext(ucontext_t *ucp)
 
 #if defined(__amd64)
 	/*
-	 * Override the fsbase in the context with the value provided through
-	 * the Linux arch_prctl(2) system call.
+	 * Override the fs/gsbase in the context with the value provided
+	 * through the Linux arch_prctl(2) system call.
 	 */
 	if (flags & LX_UC_STACK_BRAND) {
 		if (lwpd->br_lx_fsbase != 0) {
 			ucp->uc_mcontext.gregs[REG_FSBASE] = lwpd->br_lx_fsbase;
 		}
+		if (lwpd->br_lx_gsbase != 0) {
+			ucp->uc_mcontext.gregs[REG_GSBASE] = lwpd->br_lx_gsbase;
+		}
 	}
 #endif
 }

usr/src/uts/common/brand/lx/os/lx_misc.c

@@ -96,9 +96,11 @@ lx_exec()
 	 */
 	(void) lx_ptrace_stop_for_option(LX_PTRACE_O_TRACEEXEC, B_FALSE, 0, 0);
 
-	/* clear the fsbase values until the app. can reinitialize them */
+	/* clear the fs/gsbase values until the app. can reinitialize them */
 	lwpd->br_lx_fsbase = NULL;
 	lwpd->br_ntv_fsbase = NULL;
+	lwpd->br_lx_gsbase = NULL;
+	lwpd->br_ntv_gsbase = NULL;
 
 	/*
 	 * Clear the native stack flags.  This will be reinitialised by
@@ -341,9 +343,11 @@ lx_initlwp(klwp_t *lwp, void *lwpbd)
 		bcopy(plwpd->br_tls, lwpd->br_tls, sizeof (lwpd->br_tls));
 		lwpd->br_ppid = plwpd->br_pid;
 		lwpd->br_ptid = curthread->t_tid;
-		/* The child inherits the 2 fsbase values from the parent */
+		/* The child inherits the fs/gsbase values from the parent */
 		lwpd->br_lx_fsbase = plwpd->br_lx_fsbase;
 		lwpd->br_ntv_fsbase = plwpd->br_ntv_fsbase;
+		lwpd->br_lx_gsbase = plwpd->br_lx_gsbase;
+		lwpd->br_ntv_gsbase = plwpd->br_ntv_gsbase;
 	} else {
 		/*
 		 * Oddball case: the parent thread isn't a Linux process.

usr/src/uts/common/brand/lx/sys/lx_brand.h

@@ -524,6 +524,8 @@ struct lx_lwp_data {
 			/* descriptors used by libc for TLS */
 	ulong_t	br_lx_fsbase;		/* lx fsbase for 64-bit thread ptr */
 	ulong_t	br_ntv_fsbase;		/* native fsbase 64-bit thread ptr */
+	ulong_t	br_lx_gsbase;		/* lx user-land gsbase */
+	ulong_t	br_ntv_gsbase;		/* native user-land gsbase */
 	pid_t	br_pid;			/* converted pid for this thread */
 	pid_t	br_tgid;		/* thread group ID for this thread */
 	pid_t	br_ppid;		/* parent pid for this thread */

usr/src/uts/common/brand/lx/syscall/lx_thread_area.c

@@ -46,7 +46,6 @@ lx_arch_prctl(int code, ulong_t addr)
 	lx_lwp_data_t *llwp = lwptolxlwp(lwp);
 	pcb_t *pcb = &lwp->lwp_pcb;
 
-	/* We currently only support [g|s]et_fs */
 	switch (code) {
 	case LX_ARCH_GET_FS:
 		if (copyout(&llwp->br_lx_fsbase, (void *)addr,
@@ -70,6 +69,28 @@ lx_arch_prctl(int code, ulong_t addr)
 		kpreempt_enable();
 		break;
 
+	case LX_ARCH_GET_GS:
+		if (copyout(&llwp->br_lx_gsbase, (void *)addr,
+		    sizeof (llwp->br_lx_gsbase)) != 0) {
+			return (set_errno(EFAULT));
+		}
+		break;
+
+	case LX_ARCH_SET_GS:
+		llwp->br_lx_gsbase = addr;
+
+		kpreempt_disable();
+		if (pcb->pcb_gsbase != llwp->br_lx_gsbase) {
+			pcb->pcb_gsbase = llwp->br_lx_gsbase;
+
+			/*
+			 * Ensure we go out via update_sregs.
+			 */
+			pcb->pcb_rupdate = 1;
+		}
+		kpreempt_enable();
+		break;
+
 	default:
 		return (set_errno(EINVAL));
 	}

usr/src/uts/intel/brand/lx/lx_archdep.c

@@ -733,10 +733,11 @@ lx_runexe(klwp_t *lwp, void *ucp)
 		struct pcb *pcb = &lwp->lwp_pcb;
 
 		/*
-		 * Preserve the %fsbase value for this LWP, as set and used by
-		 * native illumos code.
+		 * Preserve the %fs/%gsbase value for this LWP, as set and used
+		 * by native illumos code.
 		 */
 		lwpd->br_ntv_fsbase = pcb->pcb_fsbase;
+		lwpd->br_ntv_gsbase = pcb->pcb_gsbase;
 
 		return (getsetcontext(SETCONTEXT, ucp));
 	} else {
@@ -820,6 +821,23 @@ lx_switch_to_native(klwp_t *lwp)
 			}
 			kpreempt_enable();
 		}
+		/*
+		 * ... and the correct %gsbase
+		 */
+		if (lwpd->br_ntv_gsbase != 0) {
+			struct pcb *pcb = &lwp->lwp_pcb;
+
+			kpreempt_disable();
+			if (pcb->pcb_gsbase != lwpd->br_ntv_gsbase) {
+				pcb->pcb_gsbase = lwpd->br_ntv_gsbase;
+
+				/*
+				 * Ensure we go out via update_sregs.
+				 */
+				pcb->pcb_rupdate = 1;
+			}
+			kpreempt_enable();
+		}
 		break;
 	}