commit a955bd611d6426bf7b61cab01f8ddee9cc169736
author Al Viro <viro@ftp.linux.org.uk> Thu Aug 18 20:00:49 2011 +0100
committer Richard Weinberger <richard@nod.at> Wed Nov 02 14:14:42 2011 +0100
tree f2f42f996bbb757e6f8ebd805fe1e975893dcc32
parent 3d72210bdc1ef67b72ffbd3e74873cae7287f2c6

um: series of __get_user() is costly in sigframe handling

It's not x86, where __get_user() is a single dereference; here it's
a single ptrace(2) call in host, which obviously costs a lot more.
IOW, it's cheaper to do copy_{to,from}_user() once than bother with
fields one by one...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/sys-i386/signal.c

diff --git a/arch/um/sys-i386/signal.c b/arch/um/sys-i386/signal.c
index b87195b..bcbfb0d 100644
--- a/arch/um/sys-i386/signal.c
+++ b/arch/um/sys-i386/signal.c
@@ -10,28 +10,6 @@
 #include "frame_kern.h"
 #include "skas.h"
 
-static void copy_sc(struct uml_pt_regs *regs, void *from)
-{
-	struct sigcontext *sc = from;
-
-	REGS_GS(regs->gp) = sc->gs;
-	REGS_FS(regs->gp) = sc->fs;
-	REGS_ES(regs->gp) = sc->es;
-	REGS_DS(regs->gp) = sc->ds;
-	REGS_EDI(regs->gp) = sc->di;
-	REGS_ESI(regs->gp) = sc->si;
-	REGS_EBP(regs->gp) = sc->bp;
-	REGS_SP(regs->gp) = sc->sp;
-	REGS_EBX(regs->gp) = sc->bx;
-	REGS_EDX(regs->gp) = sc->dx;
-	REGS_ECX(regs->gp) = sc->cx;
-	REGS_EAX(regs->gp) = sc->ax;
-	REGS_IP(regs->gp) = sc->ip;
-	REGS_CS(regs->gp) = sc->cs;
-	REGS_EFLAGS(regs->gp) = sc->flags;
-	REGS_SS(regs->gp) = sc->ss;
-}
-
 /*
  * FPU tag word conversions.
  */
@@ -175,7 +153,27 @@
 		return err;
 
 	pid = userspace_pid[current_thread_info()->cpu];
-	copy_sc(&regs->regs, &sc);
+
+#define GETREG(regno, regname) regs->regs.gp[HOST_##regno] = sc.regname
+
+	GETREG(GS, gs);
+	GETREG(FS, fs);
+	GETREG(ES, es);
+	GETREG(DS, ds);
+	GETREG(EDI, di);
+	GETREG(ESI, si);
+	GETREG(EBP, bp);
+	GETREG(SP, sp);
+	GETREG(EBX, bx);
+	GETREG(EDX, dx);
+	GETREG(ECX, cx);
+	GETREG(EAX, ax);
+	GETREG(IP, ip);
+	GETREG(CS, cs);
+	GETREG(EFLAGS, flags);
+	GETREG(SS, ss);
+
+#undef GETREG
 	if (have_fpx_regs) {
 		struct user_fxsr_struct fpx;
 
@@ -196,8 +194,7 @@
 			       -err);
 			return 1;
 		}
-	}
-	else {
+	} else {
 		struct user_i387_struct fp;
 
 		err = copy_from_user(&fp, sc.fpstate,
@@ -224,6 +221,7 @@
 	struct sigcontext sc;
 	struct faultinfo * fi = &current->thread.arch.faultinfo;
 	int err, pid;
+	memset(&sc, 0, sizeof(struct sigcontext));
 
 	sc.gs = REGS_GS(regs->regs.gp);
 	sc.fs = REGS_FS(regs->regs.gp);