Add support to ARM for embedding PIEs into the kernel, loading them into
genalloc pools (such as SRAM) and executing them. Support for ARM means
performing R_ARM_RELATIVE fixups within the .rel.dyn section.
Signed-off-by: Russ Dill <Russ.Dill@xxxxxx>
---
arch/arm/Kconfig | 1 +
arch/arm/Makefile | 5 +++
arch/arm/include/asm/elf.h | 1 +
arch/arm/kernel/.gitignore | 1 +
arch/arm/kernel/Makefile | 4 ++-
arch/arm/kernel/pie.c | 83 +++++++++++++++++++++++++++++++++++++++++++
arch/arm/kernel/pie.lds.S | 40 +++++++++++++++++++++
arch/arm/kernel/vmlinux.lds.S | 2 ++
arch/arm/libpie/.gitignore | 3 ++
arch/arm/libpie/Makefile | 32 +++++++++++++++++
arch/arm/libpie/empty.S | 12 +++++++
11 files changed, 183 insertions(+), 1 deletion(-)
create mode 100644 arch/arm/kernel/pie.c
create mode 100644 arch/arm/kernel/pie.lds.S
create mode 100644 arch/arm/libpie/.gitignore
create mode 100644 arch/arm/libpie/Makefile
create mode 100644 arch/arm/libpie/empty.S
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 43594d5..de7b7603 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -49,6 +49,7 @@ config ARM
select HAVE_MEMBLOCK
select HAVE_OPROFILE if (HAVE_PERF_EVENTS)
select HAVE_PERF_EVENTS
+ select HAVE_PIE
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UID16
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 6fd2cea..a673d36 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -128,6 +128,8 @@ KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/uni
CHECKFLAGS += -D__arm__
+OBJCOPY_OUTPUT_FORMAT := elf32-littlearm
+
#Default value
head-y := arch/arm/kernel/head$(MMUEXT).o
textofs-y := 0x00008000
@@ -273,6 +275,9 @@ drivers-$(CONFIG_OPROFILE) += arch/arm/oprofile/
libs-y := arch/arm/lib/ $(libs-y)
+PIE_LDS := arch/arm/kernel/pie.lds
+libpie-$(CONFIG_PIE) += arch/arm/libpie/
+
# Default target when executing plain make
ifeq ($(CONFIG_XIP_KERNEL),y)
KBUILD_IMAGE := xipImage
diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index 56211f2..a8d036b 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h
@@ -50,6 +50,7 @@ typedef struct user_fp elf_fpregset_t;
#define R_ARM_NONE 0
#define R_ARM_PC24 1
#define R_ARM_ABS32 2
+#define R_ARM_RELATIVE 23
#define R_ARM_CALL 28
#define R_ARM_JUMP24 29
#define R_ARM_V4BX 40
diff --git a/arch/arm/kernel/.gitignore b/arch/arm/kernel/.gitignore
index c5f676c..a055a48 100644
--- a/arch/arm/kernel/.gitignore
+++ b/arch/arm/kernel/.gitignore
@@ -1 +1,2 @@
vmlinux.lds
+pie.lds
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 86d10dd..652312e 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -96,4 +96,6 @@ obj-y += psci.o
obj-$(CONFIG_SMP) += psci_smp.o
endif
-extra-y := $(head-y) vmlinux.lds
+obj-$(CONFIG_PIE) += pie.o
+
+extra-y := $(head-y) vmlinux.lds pie.lds
diff --git a/arch/arm/kernel/pie.c b/arch/arm/kernel/pie.c
new file mode 100644
index 0000000..5dff5d6
--- /dev/null
+++ b/arch/arm/kernel/pie.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2013 Texas Instruments, Inc.
+ * Russ Dill <russ.dill@xxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/pie.h>
+#include <linux/elf.h>
+
+#include <asm/elf.h>
+
+extern char __pie_rel_dyn_start[];
+extern char __pie_rel_dyn_end[];
+extern char __pie_tail_offset[];
+
+struct arm_pie_tail {
+ int count;
+ uintptr_t offset[0];
+};
+
+int pie_arch_fill_tail(void *tail, void *common_start, void *common_end,
+ void *overlay_start, void *code_start, void *code_end)
+{
+ Elf32_Rel *rel;
+ int records;
+ int i;
+ struct arm_pie_tail *pie_tail = tail;
+ int count;
+
+ rel = (Elf32_Rel *) __pie_rel_dyn_start;
+ records = (__pie_rel_dyn_end - __pie_rel_dyn_start) /
+ sizeof(*rel);
+
+ count = 0;
+ for (i = 0; i < records; i++, rel++) {
+ void *kern_off;
+ if (ELF32_R_TYPE(rel->r_info) != R_ARM_RELATIVE)
+ return -ENOEXEC;
+
+ /* Adjust offset to match area in kernel */
+ kern_off = common_start + rel->r_offset;
+
+ if (kern_off >= common_start && kern_off < code_end) {
+ if (tail)
+ pie_tail->offset[count] = rel->r_offset;
+ count++;
+ } else if (kern_off >= code_start && kern_off < code_end) {
+ if (tail)
+ pie_tail->offset[count] = rel->r_offset -
+ (code_start - overlay_start);
+ count++;
+ }
+ }
+
+ if (tail)
+ pie_tail->count = count;
+
+ return count * sizeof(uintptr_t) + sizeof(*pie_tail);
+}
+EXPORT_SYMBOL_GPL(pie_arch_fill_tail);
+
+/*
+ * R_ARM_RELATIVE: B(S) + A
+ * B(S) - Addressing origin of the output segment defining the symbol S.
+ * A - Addend for the relocation.
+ */
+int pie_arch_fixup(struct pie_chunk *chunk, void *base, void *tail,
+ unsigned long offset)
+{
+ struct arm_pie_tail *pie_tail = tail;
+ int i;
+
+ /* Perform relocation fixups for given offset */
+ for (i = 0; i < pie_tail->count; i++)
+ *((uintptr_t *) (pie_tail->offset[i] + base)) += offset;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pie_arch_fixup);
diff --git a/arch/arm/kernel/pie.lds.S b/arch/arm/kernel/pie.lds.S
new file mode 100644
index 0000000..4fd5ac5
--- /dev/null
+++ b/arch/arm/kernel/pie.lds.S
@@ -0,0 +1,40 @@
+/*
+ * ld script to make ARM PIEs
+ * taken from the ARM vmlinux.lds.S version by Russ Dill <russ.dill@xxxxxx.
+ */
+
+#include <asm-generic/pie.lds.h>
+
+OUTPUT_ARCH(arm)
+
+SECTIONS
+{
+ . = 0x0;
+
+ PIE_COMMON_START
+ .got.plt : {
+ *(.got)
+ *(.got.plt)
+ }
+ .text : {
+ PIE_TEXT_TEXT
+ }
+ PIE_COMMON_END
+
+ PIE_OVERLAY_START
+ OVERLAY : NOCROSSREFS {
+ }
+ PIE_OVERLAY_SEND
+
+ __pie_rel_dyn_start : {
+ VMLINUX_SYMBOL(__pie_rel_dyn_start) = .;
+ }
+ .rel.dyn : {
+ KEEP(*(.rel*))
+ }
+ __pie_rel_dyn_end : {
+ VMLINUX_SYMBOL(__pie_rel_dyn_end) = .;
+ }
+
+ PIE_DISCARDS
+}
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 7bcee5c..8c11235 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -77,6 +77,8 @@ SECTIONS
#ifndef CONFIG_SMP_ON_UP
*(.alt.smp.init)
#endif
+ *(.pie.*)
+ *(.ARM.exidx.pie.*.text)
*(.discard)
*(.discard.*)
}
diff --git a/arch/arm/libpie/.gitignore b/arch/arm/libpie/.gitignore
new file mode 100644
index 0000000..02e3cd5
--- /dev/null
+++ b/arch/arm/libpie/.gitignore
@@ -0,0 +1,3 @@
+lib1funcs.S
+ashldi3.S
+string.c
diff --git a/arch/arm/libpie/Makefile b/arch/arm/libpie/Makefile
new file mode 100644
index 0000000..5662e99
--- /dev/null
+++ b/arch/arm/libpie/Makefile
@@ -0,0 +1,32 @@
+#
+# linux/arch/arm/libpie/Makefile
+#
+ccflags-y := -fpic -mno-single-pic-base -fno-builtin
+
+obj-y := empty.o
+obj-y += lib1funcs.o ashldi3.o string.o
+
+# string library code (-Os is enforced to keep it much smaller)
+string = $(obj)/string.o
+CFLAGS_string.o := -Os
+
+$(obj)/string.c: $(srctree)/arch/$(SRCARCH)/boot/compressed/string.c
+ $(call cmd,shipped)
+
+# For __aeabi_uidivmod
+lib1funcs = $(obj)/lib1funcs.o
+
+$(obj)/lib1funcs.S: $(srctree)/arch/$(SRCARCH)/lib/lib1funcs.S
+ $(call cmd,shipped)
+
+# For __aeabi_llsl
+ashldi3 = $(obj)/ashldi3.o
+
+$(obj)/ashldi3.S: $(srctree)/arch/$(SRCARCH)/lib/ashldi3.S
+ $(call cmd,shipped)
+
+$(obj)/libpie.o: $(string) $(lib1funcs) $(ashldi3) $(addprefix $(obj)/,$(OBJS))
+ $(call if_changed,ld)
+
+# Make sure files are removed during clean
+extra-y += string.c lib1funcs.S ashldi3.S
diff --git a/arch/arm/libpie/empty.S b/arch/arm/libpie/empty.S
new file mode 100644
index 0000000..2416862
--- /dev/null
+++ b/arch/arm/libpie/empty.S
@@ -0,0 +1,12 @@
+#include <linux/linkage.h>
+
+ENTRY(__div0)
+ENTRY(__aeabi_unwind_cpp_pr0)
+ENTRY(__aeabi_unwind_cpp_pr1)
+ENTRY(__aeabi_unwind_cpp_pr2)
+ mov pc, lr
+ENDPROC(__div0)
+ENDPROC(__aeabi_unwind_cpp_pr0)
+ENDPROC(__aeabi_unwind_cpp_pr1)
+ENDPROC(__aeabi_unwind_cpp_pr2)
+
--
1.8.3.2
--
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