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Embed APE loader inside APE (#267)

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The `ape-no-modify-self.o` bootloader now has an mmap-based
payload that helps read-only APE binaries be load faster since it
doesn't need to copy any files.
This commit is contained in:
Florian Lemaitre 2021-09-18 01:49:10 +02:00 committed by GitHub
parent b5f743cdc3
commit 18ccfeb919
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 39 additions and 3 deletions
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26
ape/ape.S
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@ -540,11 +540,30 @@ apesh: .ascii "'\n#'\"\n" # sixth edition shebang
// modify the binary to follow the local system's convention.
// There isn't a one-size-fits-all approach for this, thus we
// present two choices.
.ascii "o=\"$(command -v \"$0\")\"\n"
// Try to use a system-wide APE loader.
.ascii "type ape-loader >/dev/null 2>&1 && "
.ascii "exec ape-loader \"$o\" \"$@\"\n"
#ifdef APE_LOADER
// There is no system-wide APE loader, but there is one
// embedded inside the APE. So if the system is not MacOs,
// extract the loader into a temp folder, and use it to
// load the APE without modifying it.
.ascii "if [ ! -d /Applications ]; then\n"
.ascii "t=\"${TMPDIR:-/tmp}/ape-loader\"\n"
.ascii "[ -x \"$t\" ] || {\ndd if=\"$o\" of=\"$t\" skip=\""
.shstub ape_loader_dd_skip,2
.ascii "\" count=\""
.shstub ape_loader_dd_count,2
.ascii "\" bs=64 2>/dev/null &&\n"
.ascii "chmod 700 \"$t\"\n}\n"
.ascii "exec \"$t\" \"$o\" \"$@\"\n"
.ascii "fi\n"
#endif
#ifndef APE_NO_MODIFY_SELF
// The default behavior is: to overwrite the header in place.
// We prefer this because it's a tiny constant one time cost.
// We simply printf a 64-byte header and call execve() again.
.ascii "o=\"$(command -v \"$0\")\"\n"
#ifdef APE_BUILDSAFE
// This code is intended for binaries in build/bootstrap/. It
// causes them to not self-modify since they're checked-in to
@ -645,6 +664,11 @@ apesh: .ascii "'\n#'\"\n" # sixth edition shebang
.ascii "fi\n"
.ascii "exit $R\n"
.endobj apesh
#ifdef APE_LOADER
.section .ape.loader,"a",@progbits
.incbin APE_LOADER
.previous
#endif /* APE_LOADER */
#endif /* SupportsWindows() || SupportsMetal() || SupportsXnu() */
#if SupportsSystemv() || SupportsMetal()

12
ape/ape.lds
View file

@ -370,6 +370,15 @@ SECTIONS {
} :Ram
/*END: file content that's loaded by o/s */
/*BEGIN: payload (for now, only the APE loader) */
.payload ALIGN(64) : {
/* Loader */
HIDDEN(ape_loader = .);
KEEP(*(.ape.loader))
. = ALIGN(64);
HIDDEN(ape_loader_end = .);
}
/*END: payload */
/*BEGIN: bss memory void */
.zip . : {
@ -511,6 +520,9 @@ HIDDEN(ape_bss_filesz = 0);
HIDDEN(ape_bss_memsz = SIZEOF(.bss));
HIDDEN(ape_bss_align = PAGESIZE);
SHSTUB2(ape_loader_dd_skip, RVA(ape_loader) / 64);
SHSTUB2(ape_loader_dd_count, (ape_loader_end - ape_loader) / 64);
#if SupportsXnu()
SHSTUB2(ape_macho_dd_skip, RVA(ape_macho) / 8);
SHSTUB2(ape_macho_dd_count, (ape_macho_end - ape_macho) / 8);

4
ape/ape.mk
View file

@ -51,8 +51,8 @@ o/ape/idata.inc: \
$(APE_OBJS): $(BUILD_FILES) \
ape/ape.mk
o/$(MODE)/ape/ape-no-modify-self.o: ape/ape.S
@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -DAPE_NO_MODIFY_SELF $<
o/$(MODE)/ape/ape-no-modify-self.o: ape/ape.S o/$(MODE)/examples/loader.elf
@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -DAPE_LOADER="\"o/$(MODE)/examples/loader.elf\"" -DAPE_NO_MODIFY_SELF $<
o/$(MODE)/ape/ape-buildsafe.o: ape/ape.S
@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -DAPE_BUILDSAFE $<