Commit 78f3cdfa authored by Chris Zankel's avatar Chris Zankel
Browse files

xtensa: Fix linker script to include .literal sections



Fix resembles implementation from Marc Gauthier and Piet Denaly:

In the Xtensa architecture, assembly generates literals which must always
precede the code (the L32R instruction that loads them only uses negative
PC-relative offsets).  For any *.text section, literals are placed in a
corresponding *.literal section.  The linker script (vmlinux.lds) must
place these in the correct order.  It must also combine them, when the
*.text section can be larger than L32R's 256 kB range.

For example, this doesn't work:  *(.literal) *(.text) because L32R
instructions at the end of .text can't reach the literals.

The linker can solve this if they are combined in parentheses, like this:
       *(.literal .text)
because it is now allowed mix literals in .text to bring them in range.

None of this is done by standard vmlinux.lds.h macros such as TEXT_TEXT
and INIT_TEXT.  To avoid replicating the logic of that header file, we
instead post-process the generated linker script to convert *(xxx.text)
to *(xxx.literal xxx.text) for the following text sections:
       .text .ref.text .*init.text .*exit.text .text.*
using a sed script.  To do this we must override the default rule for
vmlinux.lds (see scripts/Makefile.build and the top-level Makefile)
to insert this extra step.
Signed-off-by: default avatarMarc Gauthier <marc@tensilica.com>
Signed-off-by: default avatarPete Delaney <piet@tensilica.com>
Signed-off-by: default avatarChris Zankel <chris@zankel.net>
parent 866e514d
......@@ -4,15 +4,30 @@
extra-y := head.o vmlinux.lds
obj-y := align.o entry.o irq.o coprocessor.o process.o ptrace.o \
setup.o signal.o syscall.o time.o traps.o vectors.o platform.o \
pci-dma.o init_task.o io.o
## windowspill.o
obj-$(CONFIG_KGDB) += xtensa-stub.o
obj-$(CONFIG_PCI) += pci.o
obj-$(CONFIG_MODULES) += xtensa_ksyms.o module.o
# In the Xtensa architecture, assembly generates literals which must always
# precede the L32R instruction with a relative offset less than 256 kB.
# Therefore, the .text and .literal section must be combined in parenthesis
# in the linker script, such as: *(.literal .text).
#
# We need to post-process the generated vmlinux.lds scripts to convert
# *(xxx.text) to *(xxx.literal xxx.text) for the following text sections:
# .text .ref.text .*init.text .*exit.text .text.*
#
# Replicate rules in scripts/Makefile.build
sed-y = -e 's/(\(\.[a-z]*it\|\.ref\|\)\.text)/(\1.literal \1.text)/g' \
-e 's/(\(\.text\.[a-z]*\))/(\1.literal \1)/g'
quiet_cmd__cpp_lds_S = LDS $@
cmd__cpp_lds_S = $(CPP) $(cpp_flags) -D__ASSEMBLY__ $< | sed $(sed-y) >$@
$(obj)/vmlinux.lds: $(src)/vmlinux.lds.S FORCE
$(call if_changed_dep,_cpp_lds_S)
......@@ -87,7 +87,7 @@ SECTIONS
{
/* The HEAD_TEXT section must be the first section! */
HEAD_TEXT
*(.literal .text)
TEXT_TEXT
VMLINUX_SYMBOL(__sched_text_start) = .;
*(.sched.literal .sched.text)
VMLINUX_SYMBOL(__sched_text_end) = .;
......@@ -139,8 +139,6 @@ SECTIONS
__init_begin = .;
.init.text : {
_sinittext = .;
*(.init.literal) *(.cpuinit.literal)
*(.devinit.literal) *(.meminit.literal)
INIT_TEXT
_einittext = .;
}
......
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