4ce97317f4
Implementing memcpy and memset in terms of __builtin_memcpy and
__builtin_memset is problematic.
GCC at -O2 will replace calls to the builtins with calls to memcpy and
memset (but will generate an inline implementation at -Os). Clang will
replace the builtins with these calls regardless of optimization level.
$ llvm-objdump -dr arch/x86/purgatory/string.o | tail
0000000000000339 memcpy:
339: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax
000000000000033b: R_X86_64_64 memcpy
343: ff e0 jmpq *%rax
0000000000000345 memset:
345: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax
0000000000000347: R_X86_64_64 memset
34f: ff e0
Such code results in infinite recursion at runtime. This is observed
when doing kexec.
Instead, reuse an implementation from arch/x86/boot/compressed/string.c.
This requires to implement a stub function for warn(). Also, Clang may
lower memcmp's that compare against 0 to bcmp's, so add a small definition,
too. See also: commit 5f074f3e19 ("lib/string.c: implement a basic bcmp")
Fixes: 8fc5b4d412 ("purgatory: core purgatory functionality")
Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Debugged-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Debugged-by: Manoj Gupta <manojgupta@google.com>
Suggested-by: Alistair Delva <adelva@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Cc: stable@vger.kernel.org
Link: https://bugs.chromium.org/p/chromium/issues/detail?id=984056
Link: https://lkml.kernel.org/r/20190807221539.94583-1-ndesaulniers@google.com
41 lines
1.3 KiB
Makefile
41 lines
1.3 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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OBJECT_FILES_NON_STANDARD := y
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purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
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targets += $(purgatory-y)
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PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
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$(obj)/string.o: $(srctree)/arch/x86/boot/compressed/string.c FORCE
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$(call if_changed_rule,cc_o_c)
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$(obj)/sha256.o: $(srctree)/lib/sha256.c FORCE
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$(call if_changed_rule,cc_o_c)
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LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
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targets += purgatory.ro
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KASAN_SANITIZE := n
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KCOV_INSTRUMENT := n
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# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
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# in turn leaves some undefined symbols like __fentry__ in purgatory and not
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# sure how to relocate those. Like kexec-tools, use custom flags.
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KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large
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KBUILD_CFLAGS += -m$(BITS)
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KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
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$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
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$(call if_changed,ld)
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targets += kexec-purgatory.c
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quiet_cmd_bin2c = BIN2C $@
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cmd_bin2c = $(objtree)/scripts/bin2c kexec_purgatory < $< > $@
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$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro FORCE
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$(call if_changed,bin2c)
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obj-$(CONFIG_KEXEC_FILE) += kexec-purgatory.o
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