MFC r277962, r277988, r282661, r282727, r282731, r283013, r283035:

  Add support for booting relocatable kernels on PowerPC.

  Add code to support loading relocatable kernels at offsets that are
  not zero.

  Move ubldr text section to the start of the output file, so that when you
  create a stripped .bin file from it the entry point is the first byte of
  the file.  (Will allow "load $addr $file ; go $addr" in u-boot.)

  Create a relocatable instance of ubldr for ARM (ubldr.bin).

  Re-link ubldr when any of its libraries change.

  An ARM kernel can be loaded at any 2MB boundary, make ubldr aware of that.

3 files changed, 72 insertions, 34 deletions

diff --git a/sys/boot/arm/uboot/Makefile b/sys/boot/arm/uboot/Makefile
index 8f718be..b4c5463 100644
--- a/sys/boot/arm/uboot/Makefile
+++ b/sys/boot/arm/uboot/Makefile
@@ -2,7 +2,8 @@
 
 .include <bsd.own.mk>
 
-PROG=		ubldr
+FILES=		ubldr ubldr.bin
+
 NEWVERSWHAT=	"U-Boot loader" ${MACHINE_ARCH}
 BINDIR?=	/boot
 INSTALLFLAGS=	-b
@@ -12,7 +13,7 @@ WARNS?=		1
 UBLDR_LOADADDR?=	0x1000000
 
 # Architecture-specific loader code
-SRCS=		start.S conf.c vers.c
+SRCS=		start.S conf.c self_reloc.c vers.c
 
 .if !defined(LOADER_NO_DISK_SUPPORT)
 LOADER_DISK_SUPPORT?=	yes
@@ -93,9 +94,7 @@ CLEANFILES+=	vers.c loader.help
 
 CFLAGS+=	-ffreestanding -msoft-float
 
-LDFLAGS=	-nostdlib -static
-LDFLAGS+=	-T ldscript.generated
-LDFLAGS+=	-T ${.CURDIR}/ldscript.${MACHINE_CPUARCH}
+LDFLAGS=	-nostdlib -static -T ${.CURDIR}/ldscript.${MACHINE_CPUARCH}
 
 # Pull in common loader code
 .PATH:		${.CURDIR}/../../uboot/common
@@ -116,6 +115,8 @@ NO_WERROR.clang=
 DPADD=		${LIBFICL} ${LIBUBOOT} ${LIBFDT} ${LIBUBOOT_FDT} ${LIBSTAND}
 LDADD=		${LIBFICL} ${LIBUBOOT} ${LIBFDT} ${LIBUBOOT_FDT} -lstand
 
+OBJS+=  ${SRCS:N*.h:R:S/$/.o/g}
+
 vers.c:	${.CURDIR}/../../common/newvers.sh ${.CURDIR}/version
 	sh ${.CURDIR}/../../common/newvers.sh ${.CURDIR}/version ${NEWVERSWHAT}
 
@@ -123,17 +124,24 @@ loader.help: help.common help.uboot ${.CURDIR}/../../fdt/help.fdt
 	cat ${.ALLSRC} | \
 	    awk -f ${.CURDIR}/../../common/merge_help.awk > ${.TARGET}
 
-${PROG}: ldscript.generated ${.CURDIR}/ldscript.${MACHINE_CPUARCH}
-
-ldscript.generated::
-	rm -f ldscript.generated.tmp
-	echo "UBLDR_LOADADDR = ${UBLDR_LOADADDR};" >ldscript.generated.tmp
-	if diff ldscript.generated ldscript.generated.tmp > /dev/null; then \
-		true; \
-	else \
-		rm -f ldscript.generated; \
-		mv ldscript.generated.tmp ldscript.generated; \
-	fi
+ldscript.abs:
+	echo "UBLDR_LOADADDR = ${UBLDR_LOADADDR};" >${.TARGET}
+
+ldscript.pie:
+	echo "UBLDR_LOADADDR = 0;" >${.TARGET}
+
+ubldr: ${OBJS} ldscript.abs ${.CURDIR}/ldscript.${MACHINE_CPUARCH} ${DPADD}
+	${CC} ${CFLAGS} -T ldscript.abs ${LDFLAGS} \
+	    -o ${.TARGET} ${OBJS} ${LDADD}
+
+ubldr.pie: ${OBJS} ldscript.pie ${.CURDIR}/ldscript.${MACHINE_CPUARCH} ${DPADD}
+	${CC} ${CFLAGS} -T ldscript.pie ${LDFLAGS} -pie -Wl,-Bsymbolic \
+	    -o ${.TARGET} ${OBJS} ${LDADD}
+
+ubldr.bin: ubldr.pie
+	${OBJCOPY} -S -O binary ubldr.pie ${.TARGET}
+
+CLEANFILES+=	ldscript.abs ldscript.pie ubldr ubldr.pie ubldr.bin
 
 .if !defined(LOADER_ONLY)
 .PATH: ${.CURDIR}/../../forth
diff --git a/sys/boot/arm/uboot/ldscript.arm b/sys/boot/arm/uboot/ldscript.arm
index b3be119..1eb10a8 100644
--- a/sys/boot/arm/uboot/ldscript.arm
+++ b/sys/boot/arm/uboot/ldscript.arm
@@ -6,6 +6,15 @@ SECTIONS
 {
   /* Read-only sections, merged into text segment: */
   . = UBLDR_LOADADDR + SIZEOF_HEADERS;
+  .text      :
+  {
+    *(.text)
+    /* .gnu.warning sections are handled specially by elf32.em.  */
+    *(.gnu.warning)
+    *(.gnu.linkonce.t*)
+  } =0
+  _etext = .;
+  PROVIDE (etext = .);
   .interp     : { *(.interp) 	}
   .hash          : { *(.hash)		}
   .dynsym        : { *(.dynsym)		}
@@ -32,15 +41,6 @@ SECTIONS
   .rela.sbss     : { *(.rela.sbss)		}
   .rela.sdata2   : { *(.rela.sdata2)		}
   .rela.sbss2    : { *(.rela.sbss2)		}
-  .text      :
-  {
-    *(.text)
-    /* .gnu.warning sections are handled specially by elf32.em.  */
-    *(.gnu.warning)
-    *(.gnu.linkonce.t*)
-  } =0
-  _etext = .;
-  PROVIDE (etext = .);
   .init      : { *(.init)    } =0
   .fini      : { *(.fini)    } =0
   .rodata    : { *(.rodata) *(.gnu.linkonce.r*) }
diff --git a/sys/boot/arm/uboot/start.S b/sys/boot/arm/uboot/start.S
index 6e8f117..1ef21f3 100644
--- a/sys/boot/arm/uboot/start.S
+++ b/sys/boot/arm/uboot/start.S
@@ -29,12 +29,38 @@
 #include <machine/asm.h>
 #include <machine/armreg.h>
 
+	.text
+	.extern	_C_LABEL(self_reloc), _C_LABEL(main)
+	.weak	_DYNAMIC
+
 /*
  * Entry point to the loader that U-Boot passes control to.
  */
-	.text
 	.globl	_start
 _start:
+
+#ifdef _ARM_ARCH_6
+	mrc     p15, 0, ip, c1, c0, 0
+	orr	ip, ip, #(CPU_CONTROL_UNAL_ENABLE)
+	orr	ip, ip, #(CPU_CONTROL_AFLT_ENABLE)
+	mcr     p15, 0, ip, c1, c0, 0
+#endif
+	/* 
+	 * Do self-relocation when the weak external symbol _DYNAMIC is non-NULL.
+	 * When linked as a dynamic relocatable file, the linker automatically
+	 * defines _DYNAMIC with a value that is the offset of the dynamic
+	 * relocation info section.
+	 * Note that we're still on u-boot's stack here, but the self_reloc 
+	 * code uses only a couple dozen bytes of stack space.
+	 */
+	adr	ip, .here_off		/* .here_off is a symbol whose value */
+	ldr	r0, [ip]		/* is its own offset in the text seg. */
+	sub	r0, ip, r0		/* Get its pc-relative address and */
+	ldr	r1, .dynamic_off	/* subtract its value and we get */
+	teq	r1, #0			/* r0 = physaddr we were loaded at. */
+	addne	r1, r1, r0		/* r1 = dynamic section physaddr. */
+	blne	_C_LABEL(self_reloc)	/* Do reloc if _DYNAMIC is non-NULL. */
+
 	/* Hint where to look for the API signature */
 	ldr	ip, =uboot_address
 	str	sp, [ip]
@@ -44,16 +70,20 @@ _start:
 	str	r8, [ip, #0]
 	str	r9, [ip, #4]
 
-#ifdef _ARM_ARCH_6
-	mrc     p15, 0, r2, c1, c0, 0
-	orr	r2, r2, #(CPU_CONTROL_UNAL_ENABLE)
-	orr	r2, r2, #(CPU_CONTROL_AFLT_ENABLE)
-	mcr     p15, 0, r2, c1, c0, 0
-#endif
-
-	/* Start loader */
+	/* 
+	 * Start loader.  This is basically a tail-recursion call; if main()
+	 * returns, it returns to u-boot (which reports the value returned r0).
+	 */
 	b	main
 
+	/* 
+	 * Data for self-relocation, in the text segment for pc-rel access.
+	 */
+.here_off:
+	.word	.
+.dynamic_off:
+	.word	_DYNAMIC
+
 /*
  * syscall()
  */