Support compiling MIPS elf trampoline with a different ABI.

Allow changing the trampoline ABI with makeoptions, this will allow
us to have a trampoline with a different ABI from the kernel.
Useful in cases where we have to boot a 64 bit kernel from a
bootloader which supports only 32 bit or vice versa.

Approved by:	bz(re), jmallett, imp

2 files changed, 45 insertions, 23 deletions

diff --git a/sys/conf/Makefile.mips b/sys/conf/Makefile.mips
index 55d57e62b192..ab2b40ac8c76 100644
--- a/sys/conf/Makefile.mips
+++ b/sys/conf/Makefile.mips
@@ -50,7 +50,13 @@ HACK_EXTRA_FLAGS=-shared
 # is extremely poor, as well as -mno-abicalls to force no ABI usage.
 CFLAGS+=${EXTRA_FLAGS} $(ARCH_FLAGS)
 HACK_EXTRA_FLAGS+=${EXTRA_FLAGS} $(ARCH_FLAGS)
-TRAMP_EXTRA_FLAGS=${EXTRA_FLAGS} $(ARCH_FLAGS)
+TRAMP_ARCH_FLAGS?=$(ARCH_FLAGS)
+TRAMP_EXTRA_FLAGS=${EXTRA_FLAGS} ${TRAMP_ARCH_FLAGS}
+.if ${MACHINE_ARCH:Mmips64*} != ""
+TRAMP_ELFSIZE=64
+.else
+TRAMP_ELFSIZE=32
+.endif
 
 # XXX hardcoded kernel entry point
 ASM_CFLAGS+=${CFLAGS} -D_LOCORE -DLOCORE
@@ -64,11 +70,12 @@ ${KERNEL_KO}.tramp.bin: ${KERNEL_KO} $S/$M/$M/elf_trampoline.c \
 	sed -e s/${KERNLOADADDR}/${TRAMPLOADADDR}/ -e s/" + SIZEOF_HEADERS"// \
 		 ${LDSCRIPT_NAME} > ${LDSCRIPT_NAME}.tramp.noheader
 	${CC} -O -nostdlib -I. -I$S ${TRAMP_EXTRA_FLAGS} ${TRAMP_LDFLAGS} -Xlinker \
-		-T -Xlinker ${LDSCRIPT_NAME}.tramp.noheader  \
-		-DKERNNAME="\"${KERNEL_KO}.tmp\"" $S/$M/$M/elf_trampoline.c \
-		$S/$M/$M/inckern.S  -o ${KERNEL_KO}.tramp.noheader 
-	${OBJCOPY} -S -O binary ${KERNEL_KO}.tramp.noheader \
-		${KERNEL_KO}.tramp.bin \
+		-T -Xlinker ${LDSCRIPT_NAME}.tramp.noheader \
+		-DKERNNAME="\"${KERNEL_KO}.tmp\"" -DELFSIZE=${TRAMP_ELFSIZE} \
+		$S/$M/$M/elf_trampoline.c $S/$M/$M/inckern.S \
+		-o ${KERNEL_KO}.tramp.elf
+	${OBJCOPY} -S -O binary ${KERNEL_KO}.tramp.elf \
+		${KERNEL_KO}.tramp.bin
 
 %BEFORE_DEPEND
 
@@ -83,7 +90,7 @@ ${KERNEL_KO}.tramp.bin: ${KERNEL_KO} $S/$M/$M/elf_trampoline.c \
 %CLEAN
 
 CLEAN+=	${LDSCRIPT_NAME} ${LDSCRIPT_NAME}.tramp.noheader \
-	${KERNEL_KO}.tramp.noheader ${KERNEL_KO}.tramp.bin
+	${KERNEL_KO}.tramp.elf ${KERNEL_KO}.tramp.bin
 
 ${LDSCRIPT_NAME}: $S/conf/${LDSCRIPT_NAME}
 	sed s/KERNLOADADDR/${KERNLOADADDR}/g $S/conf/${LDSCRIPT_NAME} \
diff --git a/sys/mips/mips/elf_trampoline.c b/sys/mips/mips/elf_trampoline.c
index 70aedebc167b..7d8324a733bf 100644
--- a/sys/mips/mips/elf_trampoline.c
+++ b/sys/mips/mips/elf_trampoline.c
@@ -27,7 +27,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/asm.h>
 #include <sys/param.h>
 
-#ifdef __mips_n64
+#if ELFSIZE == 64
 #include <sys/elf64.h>
 #else
 #include <sys/elf32.h>
@@ -90,13 +90,19 @@ bzero(void *addr, size_t count)
 }
 
 /*
+ * Convert number to pointer, truncate on 64->32 case, sign extend
+ * in 32->64 case
+ */
+#define	mkptr(x)	((void *)(intptr_t)(int)(x))
+
+/*
  * Relocate PT_LOAD segements of kernel ELF image to their respective
  * virtual addresses and return entry point
  */
 void *
 load_kernel(void * kstart)
 {
-#ifdef __mips_n64
+#if ELFSIZE == 64
 	Elf64_Ehdr *eh;
 	Elf64_Phdr phdr[64] /* XXX */;
 	Elf64_Shdr shdr[64] /* XXX */;
@@ -107,17 +113,19 @@ load_kernel(void * kstart)
 #endif
 	int i, j;
 	void *entry_point;
-	vm_offset_t lastaddr = 0;
+	vm_offset_t loadend = 0;
+	intptr_t lastaddr;
 	int symtabindex = -1;
 	int symstrindex = -1;
+	Elf_Size tmp;
 	
-#ifdef __mips_n64
+#if ELFSIZE == 64
 	eh = (Elf64_Ehdr *)kstart;
 #else
 	eh = (Elf32_Ehdr *)kstart;
 #endif
-	entry_point = (void*)eh->e_entry;
-	memcpy(phdr, (void *)(kstart + eh->e_phoff ),
+	entry_point = mkptr(eh->e_entry);
+	memcpy(phdr, (void *)(kstart + eh->e_phoff),
 	    eh->e_phnum * sizeof(phdr[0]));
 
 	memcpy(shdr, (void *)(kstart + eh->e_shoff),
@@ -147,27 +155,31 @@ load_kernel(void * kstart)
 		if (phdr[i].p_type != PT_LOAD)
 			continue;
 		
-		memcpy((void *)(phdr[i].p_vaddr),
+		memcpy(mkptr(phdr[i].p_vaddr),
 		    (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
 
 		/* Clean space from oversized segments, eg: bss. */
 		if (phdr[i].p_filesz < phdr[i].p_memsz)
-			bzero((void *)(phdr[i].p_vaddr + phdr[i].p_filesz), 
+			bzero(mkptr(phdr[i].p_vaddr + phdr[i].p_filesz),
 			    phdr[i].p_memsz - phdr[i].p_filesz);
 
-		if (lastaddr < phdr[i].p_vaddr + phdr[i].p_memsz)
-			lastaddr = phdr[i].p_vaddr + phdr[i].p_memsz;
+		if (loadend < phdr[i].p_vaddr + phdr[i].p_memsz)
+			loadend = phdr[i].p_vaddr + phdr[i].p_memsz;
 	}
 
 	/* Now grab the symbol tables. */
+	lastaddr = (intptr_t)(int)loadend;
 	if (symtabindex >= 0 && symstrindex >= 0) {
-		*(Elf_Size *)lastaddr = SYMTAB_MAGIC;
+		tmp = SYMTAB_MAGIC;
+		memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 		lastaddr += sizeof(Elf_Size);
-		*(Elf_Size *)lastaddr = shdr[symtabindex].sh_size +
+		tmp = shdr[symtabindex].sh_size +
 		    shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
+		memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 		lastaddr += sizeof(Elf_Size);
 		/* .symtab size */
-		*(Elf_Size *)lastaddr = shdr[symtabindex].sh_size;
+		tmp = shdr[symtabindex].sh_size;
+		memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 		lastaddr += sizeof(shdr[symtabindex].sh_size);
 		/* .symtab data */
 		memcpy((void*)lastaddr,
@@ -176,16 +188,19 @@ load_kernel(void * kstart)
 		lastaddr += shdr[symtabindex].sh_size;
 
 		/* .strtab size */
-		*(Elf_Size *)lastaddr = shdr[symstrindex].sh_size;
+		tmp = shdr[symstrindex].sh_size;
+		memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 		lastaddr += sizeof(shdr[symstrindex].sh_size);
 
 		/* .strtab data */
 		memcpy((void*)lastaddr,
 		    shdr[symstrindex].sh_offset + kstart,
 		    shdr[symstrindex].sh_size);
-	} else
+	} else {
 		/* Do not take any chances */
-		*(Elf_Size *)lastaddr = 0;
+		tmp = 0;
+		memcpy((void *)lastaddr, &tmp, sizeof(tmp));
+	}
 
 	return entry_point;
 }