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 <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

11 files changed, 69 insertions, 11 deletions

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 78c2b024371a..31d8965e0847 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -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) += $(call cc-option,-mtune=power7,-mtune=power4)
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 2f6ef4ed5abf..b4f0e360e414 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -7,7 +7,7 @@ CFLAGS_ptrace.o		+= -DUTS_MACHINE='"$(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 116f0868695b..1697a25ebe91 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 9f44a775a106..6ee59a0eb268 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) {
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 746e0c895cd7..fa48a4cc19a3 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -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
diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index 3787b61f7d20..cf16b5733eaa 100644
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -4,7 +4,7 @@
 
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
-ccflags-$(CONFIG_PPC64) := -mno-minimal-toc
+ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
 
 obj-y                           := fault.o mem.o pgtable.o gup.o \
                                    init_$(CONFIG_WORD_SIZE).o \
diff --git a/arch/powerpc/oprofile/Makefile b/arch/powerpc/oprofile/Makefile
index 73456c4cec28..751ec7bd5018 100644
--- a/arch/powerpc/oprofile/Makefile
+++ b/arch/powerpc/oprofile/Makefile
@@ -1,6 +1,6 @@
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
-ccflags-$(CONFIG_PPC64) := -mno-minimal-toc
+ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
 
 obj-$(CONFIG_OPROFILE) += oprofile.o
 
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 890622b87c8f..53866e537a92 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -1,4 +1,4 @@
-ccflags-$(CONFIG_PPC64)                 := -mno-minimal-toc
+ccflags-$(CONFIG_PPC64)                 := $(NO_MINIMAL_TOC)
 ccflags-$(CONFIG_PPC_PSERIES_DEBUG)     += -DDEBUG
 
 obj-y                   := lpar.o hvCall.o nvram.o reconfig.o \
diff --git a/arch/powerpc/platforms/wsp/Makefile b/arch/powerpc/platforms/wsp/Makefile
index 56817ac98fc9..162fc60125a2 100644
--- a/arch/powerpc/platforms/wsp/Makefile
+++ b/arch/powerpc/platforms/wsp/Makefile
@@ -1,4 +1,4 @@
-ccflags-y                       += -mno-minimal-toc
+ccflags-y                       += $(NO_MINIMAL_TOC)
 
 obj-y                           += setup.o ics.o wsp.o
 obj-$(CONFIG_PPC_PSR2)          += psr2.o
diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
index f44f09f3d527..eca3d19304c7 100644
--- a/arch/powerpc/sysdev/Makefile
+++ b/arch/powerpc/sysdev/Makefile
@@ -1,6 +1,6 @@
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
-ccflags-$(CONFIG_PPC64)         := -mno-minimal-toc
+ccflags-$(CONFIG_PPC64)         := $(NO_MINIMAL_TOC)
 
 mpic-msi-obj-$(CONFIG_PCI_MSI)  += mpic_msi.o mpic_u3msi.o mpic_pasemi_msi.o
 obj-$(CONFIG_MPIC)              += mpic.o $(mpic-msi-obj-y)
diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index b49fdbd15808..1278788d96e3 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -4,7 +4,7 @@ subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
 GCOV_PROFILE := n
 
-ccflags-$(CONFIG_PPC64) := -mno-minimal-toc
+ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
 
 obj-y                   += xmon.o nonstdio.o