xtensa: Fix linker script to include .literal sections (78f3cdfa) · Commits · 戴 / test

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:

Marc Gauthier <marc@tensilica.com> Signed-off-by:

Pete Delaney <piet@tensilica.com> Signed-off-by:

Chris Zankel <chris@zankel.net>

arch/xtensa/kernel/Makefile

+18 −3

Original line number	Diff line number	Diff line
		@@ -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)

arch/xtensa/kernel/vmlinux.lds.S

+1 −3

Original line number	Diff line number	Diff line
		@@ -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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