linux-rockchip/scripts/link-vmlinux.sh
Russ Dill 2ecab0b339 PIE: Support embedding position independent executables
This commit adds support for embedding PIEs into the kernel, loading them
into genalloc sections, performing necessary relocations, and running code
from them. This allows platforms that need to run code from SRAM, such
an during suspend/resume, to develop that code in C instead of assembly.

Functions and data for each PIE should be grouped into sections with the
__pie(<group>) and __pie_data(<group>) macros respectively. Any symbols or
functions that are to be accessed from outside the PIE should be marked with
EXPORT_PIE_SYMBOL(<sym>). For example:

static struct ddr_timings xyz_timings __pie_data(platformxyz) = {
	[...]
};

void __pie(platformxyz) xyz_ddr_on(void *addr)
{
	[...]
}
EXPORT_PIE_SYMBOL(xyz_ddr_on);

While the kernel can access exported symbols from the PIE, the PIE cannot
access symbols from the kernel, but can access data from the kernel and
call functions in the kernel so long as addresses are passed into the PIE.

PIEs are loaded from the kernel into a genalloc pool with pie_load_sections.
pie_load_sections allocates space within the pool, copies the neccesary
code/data, and performs any necessary relocations. A chunk identifier is
returned for removing the PIE from the pool, and for translating symbols.

Because the PIEs are dynamically relocated, special accessors must be used
to access PIE symbols from kernel code:

- kern_to_pie(chunk, ptr):   Translate a PIE symbol to the virtual address
                             it is loaded into within the pool.

- fn_to_pie(chunk, ptr):     Same as above, but for function pointers.

- sram_to_phys(chunk, addr): Translate a virtual address within a loaded PIE
                             to a physical address.

Loading a PIE involves three main steps. First a set of common functions to
cover built-ins emitted by gcc (memcpy, memmove, etc) is copied into the pool.
Then the actual PIE code and data is copied into the pool. Because the PIE
code is contained within an overlay with other PIEs, offsets to the common
functions are maintained. Finally, relocations are performed as necessary.

Signed-off-by: Russ Dill <Russ.Dill@ti.com>
2013-11-21 13:39:21 +08:00

241 lines
5.8 KiB
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#!/bin/sh
#
# link vmlinux
#
# vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_INIT) and
# $(KBUILD_VMLINUX_MAIN). Most are built-in.o files from top-level directories
# in the kernel tree, others are specified in arch/$(ARCH)/Makefile.
# Ordering when linking is important, and $(KBUILD_VMLINUX_INIT) must be first.
#
# vmlinux
# ^
# |
# +-< $(KBUILD_VMLINUX_INIT)
# | +--< init/version.o + more
# |
# +--< $(KBUILD_VMLINUX_MAIN)
# | +--< drivers/built-in.o mm/built-in.o + more
# |
# +-< ${kallsymso} (see description in KALLSYMS section)
#
# vmlinux version (uname -v) cannot be updated during normal
# descending-into-subdirs phase since we do not yet know if we need to
# update vmlinux.
# Therefore this step is delayed until just before final link of vmlinux.
#
# System.map is generated to document addresses of all kernel symbols
# Error out on error
set -e
# Nice output in kbuild format
# Will be supressed by "make -s"
info()
{
if [ "${quiet}" != "silent_" ]; then
printf " %-7s %s\n" ${1} ${2}
fi
}
# Link of vmlinux.o used for section mismatch analysis
# ${1} output file
modpost_link()
{
${LD} ${LDFLAGS} -r -o ${1} ${KBUILD_VMLINUX_INIT} \
--start-group ${KBUILD_VMLINUX_MAIN} --end-group
}
# Link of vmlinux
# ${1} - optional extra .o files
# ${2} - output file
vmlinux_link()
{
local lds="${objtree}/${KBUILD_LDS}"
if [ "${SRCARCH}" != "um" ]; then
${LD} ${LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} \
-T ${lds} ${KBUILD_VMLINUX_INIT} \
--start-group \
${KBUILD_VMLINUX_MAIN} \
${KBUILD_VMLINUX_PIE} \
--end-group ${1}
else
${CC} ${CFLAGS_vmlinux} -o ${2} \
-Wl,-T,${lds} ${KBUILD_VMLINUX_INIT} \
-Wl,--start-group \
${KBUILD_VMLINUX_MAIN} \
${KBUILD_VMLINUX_PIE} \
-Wl,--end-group \
-lutil ${1}
rm -f linux
fi
}
# Create ${2} .o file with all symbols from the ${1} object file
kallsyms()
{
info KSYM ${2}
local kallsymopt;
if [ -n "${CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX}" ]; then
kallsymopt="${kallsymopt} --symbol-prefix=_"
fi
if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
kallsymopt="${kallsymopt} --all-symbols"
fi
kallsymopt="${kallsymopt} --page-offset=$CONFIG_PAGE_OFFSET"
local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"
${NM} -n ${1} | \
scripts/kallsyms ${kallsymopt} | \
${CC} ${aflags} -c -o ${2} -x assembler-with-cpp -
}
# Create map file with all symbols from ${1}
# See mksymap for additional details
mksysmap()
{
${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
}
sortextable()
{
${objtree}/scripts/sortextable ${1}
}
# Delete output files in case of error
trap cleanup SIGHUP SIGINT SIGQUIT SIGTERM ERR
cleanup()
{
rm -f .old_version
rm -f .tmp_System.map
rm -f .tmp_kallsyms*
rm -f .tmp_version
rm -f .tmp_vmlinux*
rm -f System.map
rm -f vmlinux
rm -f vmlinux.o
}
#
#
# Use "make V=1" to debug this script
case "${KBUILD_VERBOSE}" in
*1*)
set -x
;;
esac
if [ "$1" = "clean" ]; then
cleanup
exit 0
fi
# We need access to CONFIG_ symbols
case "${KCONFIG_CONFIG}" in
*/*)
. "${KCONFIG_CONFIG}"
;;
*)
# Force using a file from the current directory
. "./${KCONFIG_CONFIG}"
esac
#link vmlinux.o
info LD vmlinux.o
modpost_link vmlinux.o
# modpost vmlinux.o to check for section mismatches
${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o
if [ -n "${CONFIG_PIE}" ]; then
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=pie
fi
# Update version
info GEN .version
if [ ! -r .version ]; then
rm -f .version;
echo 1 >.version;
else
mv .version .old_version;
expr 0$(cat .old_version) + 1 >.version;
fi;
# final build of init/
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init
kallsymso=""
kallsyms_vmlinux=""
if [ -n "${CONFIG_KALLSYMS}" ]; then
# kallsyms support
# Generate section listing all symbols and add it into vmlinux
# It's a three step process:
# 1) Link .tmp_vmlinux1 so it has all symbols and sections,
# but __kallsyms is empty.
# Running kallsyms on that gives us .tmp_kallsyms1.o with
# the right size
# 2) Link .tmp_vmlinux2 so it now has a __kallsyms section of
# the right size, but due to the added section, some
# addresses have shifted.
# From here, we generate a correct .tmp_kallsyms2.o
# 2a) We may use an extra pass as this has been necessary to
# woraround some alignment related bugs.
# KALLSYMS_EXTRA_PASS=1 is used to trigger this.
# 3) The correct ${kallsymso} is linked into the final vmlinux.
#
# a) Verify that the System.map from vmlinux matches the map from
# ${kallsymso}.
kallsymso=.tmp_kallsyms2.o
kallsyms_vmlinux=.tmp_vmlinux2
# step 1
vmlinux_link "" .tmp_vmlinux1
kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o
# step 2
vmlinux_link .tmp_kallsyms1.o .tmp_vmlinux2
kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o
# step 2a
if [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
kallsymso=.tmp_kallsyms3.o
kallsyms_vmlinux=.tmp_vmlinux3
vmlinux_link .tmp_kallsyms2.o .tmp_vmlinux3
kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o
fi
fi
info LD vmlinux
vmlinux_link "${kallsymso}" vmlinux
if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then
info SORTEX vmlinux
sortextable vmlinux
fi
info SYSMAP System.map
mksysmap vmlinux System.map
# step a (see comment above)
if [ -n "${CONFIG_KALLSYMS}" ]; then
mksysmap ${kallsyms_vmlinux} .tmp_System.map
if ! cmp -s System.map .tmp_System.map; then
echo >&2 Inconsistent kallsyms data
echo >&2 Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
cleanup
exit 1
fi
fi
# We made a new kernel - delete old version file
rm -f .old_version