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Make shell script magic less prone to breakage (#643)

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The metal boot sector code was wrapped in a single-quoted
string, like so:

    MZqFpD='
    ...MZ HEADER...
    ...E_LFANEW...
    ...BIOS BOOT SECTOR...'

This might break the shell code loader if the boot sector code
contains a 0x27 (single quote) byte.  This patch wraps the
boot sector code in a here-document instead:

    MZqFpD='
    ...MZ HEADER...' <<'@'
    ...E_LFANEW...
    ...BIOS BOOT SECTOR...
    @

This is harder to break — when interpreted as a shell script,
the code can only accidentally terminate the here-document
if there is a "\n@\n" sequence inside the BIOS boot portion.
This commit is contained in:
tkchia 2022-10-02 15:45:25 +08:00 • committed by GitHub
parent 5005f2e446
commit 3e0ddf70e9
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 3 additions and 7 deletions
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5
ape/ape.S
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@ -125,6 +125,7 @@ ape_mz: .asciz "MZqFpD='\n" # Mark 'Zibo' Joseph Zbikowski
.org 0x24 # MZ: bytes reserved for you
.ascii "JT" # MZ: OEM identifier
.short 0 # MZ: OEM information
.ascii "' <<'@'\n"
.org 0x40-4 # MZ: bytes reserved for you
#if SupportsWindows() || SupportsMetal()
.long RVA(ape_pe) # PE: the new technology
@ -250,7 +251,6 @@ pc: cld
xor %cx,%cx # current cylinder
xor %dh,%dh # current head
mov $v_ape_realsectors,%di # total sectors
sub $v_ape_realslacksectors,%di
3: call pcread
dec %di
jnz 3b
@ -549,7 +549,7 @@ ape_disk:
the bourne executable & linkable format */
#if SupportsWindows() || SupportsMetal() || SupportsXnu()
apesh: .ascii "'\n#'\"\n" # sixth edition shebang
apesh: .ascii "\n@\n#'\"\n" # sixth edition shebang
// Until all operating systems can be updated to support APE,
// we have a beautiful, yet imperfect workaround, which is to
// modify the binary to follow the local system's convention.
@ -1597,7 +1597,6 @@ kernel: movabs $ape_stack_vaddr,%rsp
.ldsvar _end
.ldsvar _etext
.ldsvar v_ape_realsectors
.ldsvar v_ape_realslacksectors
.ldsvar v_ape_highsectors
.ldsvar ape_idata_ro
.ldsvar ape_pad_rodata

3
ape/ape.lds
View file

@ -565,9 +565,6 @@ SHSTUB2(ape_loader_dd_count,
#if SupportsMetal()
HIDDEN(v_ape_realsectors =
MIN(0x70000 - IMAGE_BASE_REAL,
ROUNDUP(RVA(_edata), 4096)) / 512);
HIDDEN(v_ape_realslacksectors =
v_ape_realsectors - MIN(0x70000 - IMAGE_BASE_REAL,
ROUNDUP(RVA(_edata), 512)) / 512);
HIDDEN(v_ape_realpages = v_ape_realsectors / (4096 / 512));
HIDDEN(v_ape_highsectors =