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Provide option to have APE not modify itself
This change introduces ape-no-modify-self.o to the amalgamated release binaries, which may be used as an alternative to ape.o to make it easier to use APE in cases where the self-modifying behavior isn't acceptable. Please note that this alternative copying behavior isn't necessarily better. It introduces a whole bunch of questions of its own, which are documented in the ape.S source comment and should be considered by both the program author as well as the end-user of programs linked this way. For example, build environments that use read-only file systems and would prefer to not have a launcher wrapper (like we use in our build) can use ape-no-modify-self.o instead of ape.o and then set the $TMPDIR environment variable to point to a sane read-write-exec location. Fixes #146 See #82
This commit is contained in:
Justine Tunney
parent
59575f7e80
commit
da8a08fd58
49
ape/ape.S
49
ape/ape.S
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@ -535,7 +535,37 @@ ape_disk:
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#if SupportsWindows() || SupportsMetal() || SupportsXnu()
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apesh: .ascii "'\n#'\"\n" # sixth edition shebang
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// Until all operating systems can be updated to support APE,
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// we have a beautiful, yet imperfect workaround, which is to
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// modify the binary to follow the local system's convention.
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// There isn't a one-size-fits-all approach for this, thus we
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// present two choices.
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#ifndef APE_NO_MODIFY_SELF
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// The default behavior is: to overwrite the header in place.
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// We prefer this because it's a tiny constant one time cost.
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// We simply printf a 64-byte header and call execve() again.
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.ascii "o=\"$(command -v \"$0\")\"\n"
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#else
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// The alternative behavior is to copy to $TMPDIR and edit.
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// This imposes a variety of caveats of its own that should
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// be considered by the user beforehand, such as whether or
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// not /tmp is considered trustworthy on a given system, or
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// if the administrator chose to mount it with noexec. It's
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// up to the user to decide what's best in those situations
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// and also note that argv[0] and getauxval(AT_EXECFN) will
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// change as a result of this, and lastly note we don't try
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// to cleanup the tmp copies for the sake of efficiency. It
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// should also be noted that if $0 has directory components
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// then permission clashes can happen between system users,
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// since only root is able to set the sticky bit, which can
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// be addressed simply by overriding the TMPDIR environment
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.ascii "o=\"${TMPDIR:-/tmp}/$0\"\n"
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.ascii "if [ ! -e \"$o\" ]; then\n"
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.ascii "d=\"$o\"\n"
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.ascii "o=\"$o.$$\"\n"
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.ascii "mkdir -p \"${o%/*}\" 2>/dev/null\n"
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.ascii "cp -f \"$0\" \"$o\" || exit 120\n"
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#endif /* APE_NO_MODIFY_SELF */
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#if SupportsXnu()
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.ascii "if [ -d /Applications ]; then\n"
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.ascii "dd if=\"$o\""
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@ -547,7 +577,7 @@ apesh: .ascii "'\n#'\"\n" # sixth edition shebang
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.shstub ape_macho_dd_count,2
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.ascii "\" conv=notrunc 2>/dev/null\n"
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.ascii "el"
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#endif
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#endif /* XNU */
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.ascii "if exec 7<> \"$o\"; then\n"
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.ascii "printf '"
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.ascii "\\177ELF" # 0x0: ⌂ELF
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@ -574,19 +604,28 @@ apesh: .ascii "'\n#'\"\n" # sixth edition shebang
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.ascii "' >&7\n"
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.ascii "exec 7<&-\n"
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.ascii "else\n"
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.ascii "exit 1\n"
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.ascii "exit 121\n"
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.ascii "fi\n"
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.ascii "exec \"$0\" \"$@\"\n" # etxtbsy tail recursion
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.ascii "R=$?\n" # architecture optimistic
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#ifndef APE_NO_MODIFY_SELF
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.ascii "exec \"$0\" \"$@\"\n" # optimistic execution
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#else
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.ascii "mv -f \"$o\" \"$d\" 2>/dev/null\n"
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.ascii "o=\"$d\"\n"
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.ascii "fi\n"
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.ascii "exec \"$o\" \"$@\"\n"
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#endif /* APE_NO_MODIFY_SELF */
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.ascii "R=$?\n"
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.ascii "\n"
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.ascii "if [ $R -eq 126 ] && [ \"$(uname -m)\" != x86_64 ]; then\n"
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.ascii "if Q=\"$(command -v qemu-x86_64)\"; then\n"
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.ascii "exec \"$Q\" \"$0\" \"$@\"\n"
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.ascii "exec \"$Q\" \"$o\" \"$@\"\n"
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.ascii "else\n"
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.ascii "echo error: need qemu-x86_64 >&2\n"
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.ascii "fi\n"
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#ifndef APE_NO_MODIFY_SELF
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.ascii "elif [ $R -eq 127 ]; then\n" # means argv[0] was wrong
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.ascii " exec \"$o\" \"$@\"\n" # so do a path resolution
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#endif /* APE_NO_MODIFY_SELF */
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.ascii "fi\n"
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.ascii "exit $R\n"
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.endobj apesh
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@ -46,5 +46,10 @@ o/ape/idata.inc: \
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$(APE_OBJS): $(BUILD_FILES) \
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ape/ape.mk
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o/$(MODE)/ape/ape-no-modify-self.o: ape/ape.S
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@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -DAPE_NO_MODIFY_SELF $<
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.PHONY: o/$(MODE)/ape
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o/$(MODE)/ape: $(APE) $(APE_CHECKS)
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o/$(MODE)/ape: $(APE) \
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$(APE_CHECKS) \
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o/$(MODE)/ape/ape-no-modify-self.o
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@ -6,6 +6,7 @@ o/$(MODE)/test/libc/release/cosmopolitan.zip: \
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o/$(MODE)/ape/ape.lds \
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o/$(MODE)/libc/crt/crt.o \
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o/$(MODE)/ape/ape.o \
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o/$(MODE)/ape/ape-no-modify-self.o \
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o/$(MODE)/cosmopolitan.a
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@$(COMPILE) -AZIP -T$@ zip -j $@ $^
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@ -37,6 +38,30 @@ o/$(MODE)/test/libc/release/smoke.com.dbg: \
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o/$(MODE)/ape/ape.o \
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o/$(MODE)/cosmopolitan.a
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o/$(MODE)/test/libc/release/smoke-nms.com.dbg: \
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test/libc/release/smoke.c \
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o/cosmopolitan.h \
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o/$(MODE)/ape/ape.lds \
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o/$(MODE)/libc/crt/crt.o \
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o/$(MODE)/ape/ape-no-modify-self.o \
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o/$(MODE)/cosmopolitan.a
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@$(COMPILE) -ACC $(CC) \
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-o $@ \
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-Os \
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-static \
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-no-pie \
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-fno-pie \
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-nostdlib \
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-nostdinc \
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-mno-red-zone \
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-fno-omit-frame-pointer \
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-Wl,-T,o/$(MODE)/ape/ape.lds \
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-include o/cosmopolitan.h \
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test/libc/release/smoke.c \
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o/$(MODE)/libc/crt/crt.o \
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o/$(MODE)/ape/ape-no-modify-self.o \
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o/$(MODE)/cosmopolitan.a
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o/$(MODE)/test/libc/release/smokecxx.com: \
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o/$(MODE)/test/libc/release/smokecxx.com.dbg
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@$(COMPILE) -AOBJCOPY -T$< $(OBJCOPY) -S -O binary $< $@
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@ -116,6 +141,8 @@ o/$(MODE)/test/libc/release/emulate.ok: \
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o/$(MODE)/test/libc/release: \
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o/$(MODE)/test/libc/release/smoke.com \
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o/$(MODE)/test/libc/release/smoke.com.runs \
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o/$(MODE)/test/libc/release/smoke-nms.com \
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o/$(MODE)/test/libc/release/smoke-nms.com.runs \
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o/$(MODE)/test/libc/release/smokecxx.com \
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o/$(MODE)/test/libc/release/smokecxx.com.runs \
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o/$(MODE)/test/libc/release/smokeansi.com \
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