powerpc: Minimal private libgcc to build on Debian

Standard Debian powerpc and powerpcspe systems only include hard-float
libgcc in their native compilers, which causes scary build warnings when
building U-Boot.

Debian and other PowerPC-supporting distributions used to provide libgcc
and other libraries in a "nof" (soft-float) form in the "multilib"
packages.  As they were completely unused by the distribution and
therefore tended to be very buggy it was decided to save some time on
the part of the maintainers and build-servers by removing them.

Admittedly, right now the linker warnings do not indicate any problems,
as the included routines do not use any floating point at all.

The concern is that if floating-point code were ever added it might
cause hard-float code to be unexpectedly included in U-Boot without
generating a hard error.  This would cause unexplained crashes or
indeterminate results at runtime.

The easiest way to resolve this is to borrow the routines that U-Boot
needs from the Linux kernel, which has the same issue.

Specifically, the routines are: _ashldi3(), _ashrdi3(), and _lshrdi3().
They were borrowed from arch/powerpc/kernel/misc_32.S as of v2.6.38-rc5,
commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, and are GPLv2+.

The Makefile framework was copied from the U-Boot ARM port.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Kim Phillips <kim.phillips@freescale.com>
Cc: Andy Fleming <afleming@gmail.com>
Cc: Kumar Gala <kumar.gala@freescale.com>
Cc: Stefan Roese <sr@denx.de>

4 files changed, 159 insertions, 1 deletions

diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 724d8ee7f7..cdd62a2061 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -23,6 +23,19 @@
 
 include $(TOPDIR)/config.mk
 
+## Build a couple of necessary functions into a private libgcc
+LIBGCC	= $(obj)libgcc.o
+GLSOBJS	+= _ashldi3.o
+GLSOBJS	+= _ashrdi3.o
+GLSOBJS	+= _lshrdi3.o
+LGOBJS	:= $(addprefix $(obj),$(GLSOBJS)) \
+	   $(addprefix $(obj),$(GLCOBJS))
+
+## But only build it if the user asked for it
+ifdef USE_PRIVATE_LIBGCC
+TARGETS	+= $(LIBGCC)
+endif
+
 LIB	= $(obj)lib$(ARCH).o
 
 SOBJS-y	+= ppccache.o
@@ -53,9 +66,14 @@ endif
 
 COBJS	+= $(sort $(COBJS-y))
 
-SRCS	:= $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
+SRCS	:= $(GLSOBJS:.o=.S) $(GLCOBJS:.o=.c) \
+	   $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS-y) $(COBJS-y))
 
+TARGETS += $(LIB)
+
+all: $(TARGETS)
+
 $(LIB):	$(obj).depend $(OBJS)
 	@if ! $(CROSS_COMPILE)readelf -S $(OBJS) | grep -q '\.fixup.*PROGBITS';\
 	then \
@@ -65,6 +83,9 @@ $(LIB):	$(obj).depend $(OBJS)
 	fi;
 	$(call cmd_link_o_target, $(OBJS))
 
+$(LIBGCC): $(obj).depend $(LGOBJS)
+	$(call cmd_link_o_target, $(LGOBJS))
+
 #########################################################################
 
 # defines $(obj).depend target
diff --git a/arch/powerpc/lib/_ashldi3.S b/arch/powerpc/lib/_ashldi3.S
new file mode 100644
index 0000000000..e452f56de5
--- /dev/null
+++ b/arch/powerpc/lib/_ashldi3.S
@@ -0,0 +1,45 @@
+/*
+ * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
+ * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
+ * known as 2.6.38-rc5).  The source file copyrights are as follows:
+ *
+ * (C) Copyright 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
+ * and Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <ppc_asm.tmpl>
+#include <ppc_defs.h>
+#include <config.h>
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5    has shift count
+ * result in R3/R4
+ *
+ *  ashrdi3: arithmetic right shift (sign propagation)
+ *  lshrdi3: logical right shift
+ *  ashldi3: left shift
+ */
+	.globl __ashldi3
+__ashldi3:
+	subfic	r6,r5,32
+	slw	r3,r3,r5	# MSW = count > 31 ? 0 : MSW << count
+	addi	r7,r5,32	# could be xori, or addi with -32
+	srw	r6,r4,r6	# t1 = count > 31 ? 0 : LSW >> (32-count)
+	slw	r7,r4,r7	# t2 = count < 32 ? 0 : LSW << (count-32)
+	or	r3,r3,r6	# MSW |= t1
+	slw	r4,r4,r5	# LSW = LSW << count
+	or	r3,r3,r7	# MSW |= t2
+	blr
diff --git a/arch/powerpc/lib/_ashrdi3.S b/arch/powerpc/lib/_ashrdi3.S
new file mode 100644
index 0000000000..f28ab49764
--- /dev/null
+++ b/arch/powerpc/lib/_ashrdi3.S
@@ -0,0 +1,47 @@
+/*
+ * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
+ * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
+ * known as 2.6.38-rc5).  The source file copyrights are as follows:
+ *
+ * (C) Copyright 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
+ * and Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <ppc_asm.tmpl>
+#include <ppc_defs.h>
+#include <config.h>
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5    has shift count
+ * result in R3/R4
+ *
+ *  ashrdi3: arithmetic right shift (sign propagation)
+ *  lshrdi3: logical right shift
+ *  ashldi3: left shift
+ */
+	.globl __ashrdi3
+__ashrdi3:
+	subfic	r6,r5,32
+	srw	r4,r4,r5	# LSW = count > 31 ? 0 : LSW >> count
+	addi	r7,r5,32	# could be xori, or addi with -32
+	slw	r6,r3,r6	# t1 = count > 31 ? 0 : MSW << (32-count)
+	rlwinm	r8,r7,0,32	# t3 = (count < 32) ? 32 : 0
+	sraw	r7,r3,r7	# t2 = MSW >> (count-32)
+	or	r4,r4,r6	# LSW |= t1
+	slw	r7,r7,r8	# t2 = (count < 32) ? 0 : t2
+	sraw	r3,r3,r5	# MSW = MSW >> count
+	or	r4,r4,r7	# LSW |= t2
+	blr
diff --git a/arch/powerpc/lib/_lshrdi3.S b/arch/powerpc/lib/_lshrdi3.S
new file mode 100644
index 0000000000..c1bbe7be3e
--- /dev/null
+++ b/arch/powerpc/lib/_lshrdi3.S
@@ -0,0 +1,45 @@
+/*
+ * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
+ * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
+ * known as 2.6.38-rc5).  The source file copyrights are as follows:
+ *
+ * (C) Copyright 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ * Largely rewritten by Cort Dougan (cort@cs.nmt.edu)
+ * and Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <ppc_asm.tmpl>
+#include <ppc_defs.h>
+#include <config.h>
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5    has shift count
+ * result in R3/R4
+ *
+ *  ashrdi3: arithmetic right shift (sign propagation)
+ *  lshrdi3: logical right shift
+ *  ashldi3: left shift
+ */
+	.globl __lshrdi3
+__lshrdi3:
+	subfic	r6,r5,32
+	srw	r4,r4,r5	# LSW = count > 31 ? 0 : LSW >> count
+	addi	r7,r5,32	# could be xori, or addi with -32
+	slw	r6,r3,r6	# t1 = count > 31 ? 0 : MSW << (32-count)
+	srw	r7,r3,r7	# t2 = count < 32 ? 0 : MSW >> (count-32)
+	or	r4,r4,r6	# LSW |= t1
+	srw	r3,r3,r5	# MSW = MSW >> count
+	or	r4,r4,r7	# LSW |= t2
+	blr