From 1fbe9cf2598dae3bd464d860bd89c67b1ff8682b Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 26 Nov 2012 17:41:08 +0000 Subject: 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: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/Makefile | 2 +- arch/powerpc/kernel/head_64.S | 15 +++++++++++++-- arch/powerpc/kernel/module_64.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 44 insertions(+), 3 deletions(-) (limited to 'arch/powerpc/kernel') diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 2f6ef4ed5ab..b4f0e360e41 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -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 diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S index 116f0868695..1697a25ebe9 100644 --- a/arch/powerpc/kernel/head_64.S +++ b/arch/powerpc/kernel/head_64.S @@ -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) */ - bl .relative_toc + /* 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 diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index 9f44a775a10..6ee59a0eb26 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -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) { -- cgit v1.2.3