Commit 1fbe9cf2 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

powerpc: Build kernel with -mcmodel=medium 



Finally remove the two level TOC and build with -mcmodel=medium.

Unfortunately we can't build modules with -mcmodel=medium due to
the tricks the kernel module loader plays with percpu data:

# -mcmodel=medium breaks modules because it uses 32bit offsets from
# the TOC pointer to create pointers where possible. Pointers into the
# percpu data area are created by this method.
#
# The kernel module loader relocates the percpu data section from the
# original location (starting with 0xd...) to somewhere in the base
# kernel percpu data space (starting with 0xc...). We need a full
# 64bit relocation for this to work, hence -mcmodel=large.

On older kernels we fall back to the two level TOC (-mminimal-toc)

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 5827d416

arch/powerpc/Makefile

+18 −1
Original line number Diff line number Diff line
@@ -67,7 +67,24 @@ LDFLAGS_vmlinux-y := -Bstatic 
LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie

LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)



CFLAGS-$(CONFIG_PPC64)	:= -mminimal-toc -mtraceback=no -mcall-aixdesc

ifeq ($(CONFIG_PPC64),y)

ifeq ($(call cc-option-yn,-mcmodel=medium),y)

	# -mcmodel=medium breaks modules because it uses 32bit offsets from

	# the TOC pointer to create pointers where possible. Pointers into the

	# percpu data area are created by this method.

	#

	# The kernel module loader relocates the percpu data section from the

	# original location (starting with 0xd...) to somewhere in the base

	# kernel percpu data space (starting with 0xc...). We need a full

	# 64bit relocation for this to work, hence -mcmodel=large.

	KBUILD_CFLAGS_MODULE += -mcmodel=large

else

	export NO_MINIMAL_TOC := -mno-minimal-toc

endif

endif



CFLAGS-$(CONFIG_PPC64)	:= -mtraceback=no -mcall-aixdesc

CFLAGS-$(CONFIG_PPC64)	+= $(call cc-option,-mcmodel=medium,-mminimal-toc)

CFLAGS-$(CONFIG_PPC32)	:= -ffixed-r2 -mmultiple



CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power7,-mtune=power4)

arch/powerpc/kernel/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -7,7 +7,7 @@ CFLAGS_ptrace.o += -DUTS_MACHINE='"$(UTS_MACHINE)"' 
subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror



ifeq ($(CONFIG_PPC64),y)

CFLAGS_prom_init.o	+= -mno-minimal-toc

CFLAGS_prom_init.o	+= $(NO_MINIMAL_TOC)

endif

ifeq ($(CONFIG_PPC32),y)

CFLAGS_prom_init.o      += -fPIC

arch/powerpc/kernel/head_64.S

+13 −2
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ _GLOBAL(generic_secondary_thread_init) 


	/* get a valid TOC pointer, wherever we're mapped at */

	bl	.relative_toc

	tovirt(r2,r2)



#ifdef CONFIG_PPC_BOOK3E

	/* Book3E initialization */
@@ -195,6 +196,7 @@ _GLOBAL(generic_secondary_smp_init) 


	/* get a valid TOC pointer, wherever we're mapped at */

	bl	.relative_toc

	tovirt(r2,r2)



#ifdef CONFIG_PPC_BOOK3E

	/* Book3E initialization */
@@ -531,6 +533,7 @@ _GLOBAL(pmac_secondary_start) 


	/* get TOC pointer (real address) */

	bl	.relative_toc

	tovirt(r2,r2)



	/* Copy some CPU settings from CPU 0 */

	bl	.__restore_cpu_ppc970
@@ -665,6 +668,13 @@ _GLOBAL(enable_64b_mode) 
 * This puts the TOC pointer into r2, offset by 0x8000 (as expected

 * by the toolchain).  It computes the correct value for wherever we

 * are running at the moment, using position-independent code.

 *

 * Note: The compiler constructs pointers using offsets from the

 * TOC in -mcmodel=medium mode. After we relocate to 0 but before

 * the MMU is on we need our TOC to be a virtual address otherwise

 * these pointers will be real addresses which may get stored and

 * accessed later with the MMU on. We use tovirt() at the call

 * sites to handle this.

 */

_GLOBAL(relative_toc)

	mflr	r0
@@ -681,8 +691,9 @@ p_toc: .llong __toc_start + 0x8000 - 0b 
 * This is where the main kernel code starts.

 */

_INIT_STATIC(start_here_multiplatform)

	/* set up the TOC (real address) */

	/* set up the TOC */

	bl      .relative_toc

	tovirt(r2,r2)



	/* Clear out the BSS. It may have been done in prom_init,

	 * already but that's irrelevant since prom_init will soon

arch/powerpc/kernel/module_64.c

+30 −0
Original line number Diff line number Diff line
@@ -386,6 +386,14 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, 
				| (value & 0xffff);

			break;



		case R_PPC64_TOC16_LO:

			/* Subtract TOC pointer */

			value -= my_r2(sechdrs, me);

			*((uint16_t *) location)

				= (*((uint16_t *) location) & ~0xffff)

				| (value & 0xffff);

			break;



		case R_PPC64_TOC16_DS:

			/* Subtract TOC pointer */

			value -= my_r2(sechdrs, me);
@@ -399,6 +407,28 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, 
				| (value & 0xfffc);

			break;



		case R_PPC64_TOC16_LO_DS:

			/* Subtract TOC pointer */

			value -= my_r2(sechdrs, me);

			if ((value & 3) != 0) {

				printk("%s: bad TOC16_LO_DS relocation (%lu)\n",

				       me->name, value);

				return -ENOEXEC;

			}

			*((uint16_t *) location)

				= (*((uint16_t *) location) & ~0xfffc)

				| (value & 0xfffc);

			break;



		case R_PPC64_TOC16_HA:

			/* Subtract TOC pointer */

			value -= my_r2(sechdrs, me);

			value = ((value + 0x8000) >> 16);

			*((uint16_t *) location)

				= (*((uint16_t *) location) & ~0xffff)

				| (value & 0xffff);

			break;



		case R_PPC_REL24:

			/* FIXME: Handle weak symbols here --RR */

			if (sym->st_shndx == SHN_UNDEF) {

arch/powerpc/lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 


subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror



ccflags-$(CONFIG_PPC64)	:= -mno-minimal-toc

ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)



CFLAGS_REMOVE_code-patching.o = -pg

CFLAGS_REMOVE_feature-fixups.o = -pg

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