QEMU loads the unit test, but due to the way it translates the
unit test's linker VMA to the LMA, we can't just link such that
VMA == LMA. Thus, we link with VMA == 0x0, and then deal with
relocation.
Signed-off-by: Andrew Jones <drjo...@redhat.com>
---
configure | 2 ++
powerpc/Makefile.common | 13 +++++++++---
powerpc/Makefile.ppc64 | 1 +
powerpc/cstart64.S | 40 +++++++++++++++++++++++++++++++----
powerpc/flat.lds | 13 +++++++++++-
powerpc/reloc64.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 116 insertions(+), 8 deletions(-)
create mode 100644 powerpc/reloc64.c
diff --git a/configure b/configure
index b367224093369..b2ad199da7873 100755
--- a/configure
+++ b/configure
@@ -5,6 +5,7 @@ kerneldir=/lib/modules/$(uname -r)/build
cc=gcc
ld=ld
objcopy=objcopy
+objdump=objdump
ar=ar
arch=`uname -m | sed -e s/i.86/i386/ | sed -e 's/arm.*/arm/'`
host=$arch
@@ -132,6 +133,7 @@ PROCESSOR=$processor
CC=$cross_prefix$cc
LD=$cross_prefix$ld
OBJCOPY=$cross_prefix$objcopy
+OBJDUMP=$cross_prefix$objdump
AR=$cross_prefix$ar
API=$api
TEST_DIR=$testdir
diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
index d6356540918a5..b130342dee60e 100644
--- a/powerpc/Makefile.common
+++ b/powerpc/Makefile.common
@@ -27,6 +27,7 @@ CFLAGS += -Wextra
CFLAGS += -O2
CFLAGS += -I lib -I lib/libfdt
CFLAGS += -Wa,-mregnames
+CFLAGS += -fpie
asm-offsets = lib/$(ARCH)/asm-offsets.h
include scripts/asm-offsets.mak
@@ -43,11 +44,17 @@ libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name)
start_addr := $(shell printf "%x\n" $$(( $(phys_base) + $(kernel_offset) )))
FLATLIBS = $(libcflat) $(LIBFDT_archive) $(libgcc)
-%.elf: LDFLAGS = $(CFLAGS) -nostdlib
+%.elf: LDFLAGS = $(CFLAGS) -nostdlib -pie
%.elf: %.o $(FLATLIBS) powerpc/flat.lds
$(CC) $(LDFLAGS) -o $@ \
-Wl,-T,powerpc/flat.lds,--build-id=none,-Ttext=$(start_addr) \
$(filter %.o, $^) $(FLATLIBS)
+ @echo -n Checking $@ for unsupported reloc types...
+ @if $(OBJDUMP) -R $@ | grep R_ | grep -v R_PPC64_RELATIVE; then \
+ false; \
+ else \
+ echo " looks good."; \
+ fi
powerpc_clean: libfdt_clean asm_offsets_clean
$(RM) $(TEST_DIR)/*.{o,elf} \
@@ -59,5 +66,5 @@ generated_files = $(asm-offsets)
test_cases: $(generated_files) $(tests-common) $(tests)
-$(TEST_DIR)/$(TEST).elf: $(cstart.o) $(TEST_DIR)/$(TEST).o
-$(TEST_DIR)/selftest.elf: $(cstart.o) $(TEST_DIR)/selftest.o
+$(TEST_DIR)/$(TEST).elf: $(cstart.o) $(reloc.o) $(TEST_DIR)/$(TEST).o
+$(TEST_DIR)/selftest.elf: $(cstart.o) $(reloc.o) $(TEST_DIR)/selftest.o
diff --git a/powerpc/Makefile.ppc64 b/powerpc/Makefile.ppc64
index 7c61933dfa8ba..7274e0d98b5a5 100644
--- a/powerpc/Makefile.ppc64
+++ b/powerpc/Makefile.ppc64
@@ -8,6 +8,7 @@ ldarch = elf64-powerpc #elf64-powerpcle (eventually)
kernel_offset = 0x0
cstart.o = $(TEST_DIR)/cstart64.o
+reloc.o = $(TEST_DIR)/reloc64.o
cflatobjs += lib/ppc64/processor.o
cflatobjs += lib/ppc64/spinlock.o
diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
index 141d4563563d5..8edaaa6e251fc 100644
--- a/powerpc/cstart64.S
+++ b/powerpc/cstart64.S
@@ -26,18 +26,50 @@
*/
.globl start
start:
- LOAD_REG_IMMEDIATE(r1, stackptr)
- LOAD_REG_IMMEDIATE(r2, tocptr)
+ /*
+ * We were loaded at QEMU's kernel load address, but we're not
+ * allowed to link there due to how QEMU deals with linker VMAs,
+ * so we just linked at zero. This means the first thing to do is
+ * to find our stack and toc, and then do a relocate.
+ */
+ bl . + 4
+0: mflr r31
+ subi r31, r31, 0b - start /* QEMU's kernel load address */
+ ld r1, (p_stack - start)(r31)
+ ld r2, (p_toc - start)(r31)
+ add r1, r1, r31
+ add r2, r2, r31
+
+ /* save DTB pointer */
+ std r3, 56(r1)
+
+ /*
+ * Call relocate. relocate is C code, but careful to not use
+ * any global references, as they may use absolute addresses,
+ * which are, obviously, not yet relocated.
+ */
+ mr r3, r31
+ ld r4, (p_dyn - start)(r31)
+ add r4, r4, r31
+ bl .relocate
+
+ /* complete setup */
+ ld r3, 56(r1)
bl .setup
/* run the test */
- LOAD_REG_IMMEDIATE(r5, __argc)
- LOAD_REG_IMMEDIATE(r4, __argv)
+ LOAD_REG_ADDR(r5, __argc)
+ LOAD_REG_ADDR(r4, __argv)
lwz r3, 0(r5)
bl .main
bl .exit
b halt
+.align 3
+p_stack: .llong stackptr
+p_toc: .llong tocptr
+p_dyn: .llong dynamic_start
+
.text
.align 3
diff --git a/powerpc/flat.lds b/powerpc/flat.lds
index bd075efb2c51b..8a573d27346de 100644
--- a/powerpc/flat.lds
+++ b/powerpc/flat.lds
@@ -6,11 +6,22 @@ SECTIONS
etext = .;
.opd : { *(.opd) }
. = ALIGN(16);
+ .dynamic : {
+ dynamic_start = .;
+ *(.dynamic)
+ }
+ .dynsym : {
+ dynsym_start = .;
+ *(.dynsym)
+ }
+ .rela.dyn : { *(.rela*) }
+ . = ALIGN(16);
.data : {
*(.data)
+ *(.data.rel*)
}
. = ALIGN(16);
- .rodata : { *(.rodata) }
+ .rodata : { *(.rodata) *(.rodata.*) }
. = ALIGN(16);
.bss : { *(.bss) }
. = ALIGN(16);
diff --git a/powerpc/reloc64.c b/powerpc/reloc64.c
new file mode 100644
index 0000000000000..2804823bdfee3
--- /dev/null
+++ b/powerpc/reloc64.c
@@ -0,0 +1,55 @@
+/*
+ * relocate R_PPC_RELATIVE RELA entries. Normally this is done in
+ * assembly code to avoid the risk of using absolute addresses before
+ * they're relocated. We use C, but cautiously (no global references).
+ *
+ * Copyright (C) 2015, Red Hat Inc, Andrew Jones <drjo...@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.
+ */
+#define DT_NULL 0
+#define DT_RELA 7
+#define DT_RELACOUNT 0x6ffffff9
+#define R_PPC_RELATIVE 22
+
+struct elf64_dyn {
+ signed long long tag;
+ unsigned long long val;
+};
+
+#define RELA_GET_TYPE(rela_ptr) ((rela_ptr)->info & 0xffffffff)
+struct elf64_rela {
+ unsigned long long offset;
+ unsigned long long info;
+ signed long long addend;
+};
+
+void relocate(unsigned long load_addr, struct elf64_dyn *dyn_table)
+{
+ unsigned long long rela_addr = 0, rela_count = 0, *addr;
+ struct elf64_dyn *d = dyn_table;
+ struct elf64_rela *r;
+
+ while (d && d->tag != DT_NULL) {
+ if (d->tag == DT_RELA)
+ rela_addr = d->val;
+ else if (d->tag == DT_RELACOUNT)
+ rela_count = d->val;
+ if (rela_addr && rela_count)
+ break;
+ ++d;
+ }
+
+ if (!rela_addr || !rela_count)
+ return;
+
+ r = (void *)(rela_addr + load_addr);
+
+ while (rela_count--) {
+ if (RELA_GET_TYPE(r) == R_PPC_RELATIVE) {
+ addr = (void *)(r->offset + load_addr);
+ *addr = r->addend + load_addr;
+ }
+ ++r;
+ }
+}
--
2.4.3
--
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