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Fix execution bug w/o binfmt_misc

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The longjmp relocation in the master boot record coincidentally had a
quote character in it, which caused the master boot record to be used
when interpreter by the shell. The solution, is to move the grub stub
below the long mode loader so the real mode loader relocation is near
the master boot record. This change includes a regression test.
This commit is contained in:
Justine Tunney 2022-05-25 17:19:46 -07:00
parent 1a29424c52
commit 8f12cd980d
3 changed files with 61 additions and 46 deletions
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83
ape/ape.S
View file

@ -553,6 +553,7 @@ apesh: .ascii "'\n#'\"\n" # sixth edition shebang
.ascii "[ x\"$1\" != x--assimilate ] && {\n"
.ascii "t=\"${TMPDIR:-/tmp}/ape\"\n"
.ascii "[ -x \"$t\" ] || {\n"
.ascii "mkdir -p \"${t%/*}\" &&\n"
.ascii "dd if=\"$o\" of=\"$t.$$\" skip=\""
.shstub ape_loader_dd_skip,2
.ascii "\" count=\""
@ -1168,47 +1169,6 @@ gdt: .short 2f-1f # table byte length
.quad 0b0000000010101111100100110000000000000000000000001111111111111111 #48
2: .endobj gdt,global,hidden
/*─────────────────────────────────────────────────────────────────────────────╗
│ αcτµαlly pδrταblε εxεcµταblε § multiboot stub │
╚──────────────────────────────────────────────────────────────────────────────╝
boot modernized for the nineties */
#define GRUB_MAGIC 0x1BADB002
#define GRUB_EAX 0x2BADB002
#define GRUB_AOUT (1 << 16)
#define GRUB_CHECKSUM(FLAGS) (-(GRUB_MAGIC + (FLAGS)) & 0xffffffff)
// Grub Header.
.align 4
ape_grub:
.long GRUB_MAGIC # Magic
.long GRUB_AOUT # Flags
.long GRUB_CHECKSUM(GRUB_AOUT) # Checksum
.long RVA(ape_grub) # HeaderPhysicalAddress
.long IMAGE_BASE_PHYSICAL # TextPhysicalAddress
.long PHYSICAL(_edata) # LoadEndPhysicalAddress
.long PHYSICAL(_end) # BssEndPhysicalAddress
.long RVA(ape_grub_entry) # EntryPhysicalAddress
.endobj ape_grub,globl
// Grub Entrypoint.
// Takes CPU out of legacy mode and jumps to normal entrypoint.
// @noreturn
.align 4
ape_grub_entry:
.code32
// cmp $GRUB_EAX,%eax
// jne triplf
push $0
popf
mov $0x40,%dl
mov %cr0,%eax
and $~CR0_PE,%eax
mov %eax,%cr0
ljmpw $0,$REAL(pc)
.code16
.endfn ape_grub_entry
/*─────────────────────────────────────────────────────────────────────────────╗
│ αcτµαlly pδrταblε εxεcµταblε § real mode │
╚──────────────────────────────────────────────────────────────────────────────╝
@ -1485,6 +1445,47 @@ long: push $GDT_LONG_DATA
jmp *%rax
.endfn long
/*─────────────────────────────────────────────────────────────────────────────╗
│ αcτµαlly pδrταblε εxεcµταblε § multiboot stub │
╚──────────────────────────────────────────────────────────────────────────────╝
boot modernized for the nineties */
#define GRUB_MAGIC 0x1BADB002
#define GRUB_EAX 0x2BADB002
#define GRUB_AOUT (1 << 16)
#define GRUB_CHECKSUM(FLAGS) (-(GRUB_MAGIC + (FLAGS)) & 0xffffffff)
// Grub Header.
.align 4
ape_grub:
.long GRUB_MAGIC # Magic
.long GRUB_AOUT # Flags
.long GRUB_CHECKSUM(GRUB_AOUT) # Checksum
.long RVA(ape_grub) # HeaderPhysicalAddress
.long IMAGE_BASE_PHYSICAL # TextPhysicalAddress
.long PHYSICAL(_edata) # LoadEndPhysicalAddress
.long PHYSICAL(_end) # BssEndPhysicalAddress
.long RVA(ape_grub_entry) # EntryPhysicalAddress
.endobj ape_grub,globl
// Grub Entrypoint.
// Takes CPU out of legacy mode and jumps to normal entrypoint.
// @noreturn
.align 4
ape_grub_entry:
.code32
// cmp $GRUB_EAX,%eax
// jne triplf
push $0
popf
mov $0x40,%dl
mov %cr0,%eax
and $~CR0_PE,%eax
mov %eax,%cr0
ljmpw $0,$REAL(pc)
.code64
.endfn ape_grub_entry
/* ▄▄▒▀▀▀▀▒▒▄
█████▓▓▄░░░░ ▒▒▄
▐█▓▓█▓▄█████▓░ ▀▒▄

14
test/libc/runtime/ape_test.c
View file

@ -105,6 +105,20 @@ void RunApeTest(const char *path) {
EXPECT_STREQN("MZqFpD", buf, 6);
}
TEST(ape, noAccidentalQuotesInMasterBootRecord) {
int i, quotes = 0;
char buf[512] = {0};
EXPECT_SYS(0, 3, open("bin/apetest.com", O_RDONLY));
EXPECT_SYS(0, 512, read(3, buf, 512));
EXPECT_SYS(0, 0, close(3));
for (i = 0; i < 512; ++i) {
if (buf[i] == '\'') {
++quotes;
}
}
EXPECT_EQ(1, quotes);
}
TEST(apeNoModifySelf, runsWithoutModifyingSelf) {
RunApeTest("bin/apetest.com");
}

10
third_party/chibicc/chibicc.mk vendored
View file

@ -10,8 +10,8 @@
# This makefile compiles and runs each test twice. The first with
# GCC-built chibicc, and a second time with chibicc-built chibicc
CHIBICC = o/$(MODE)/third_party/chibicc/chibicc.com.dbg
CHIBICC2 = o/$(MODE)/third_party/chibicc/chibicc2.com.dbg
CHIBICC = o/$(MODE)/third_party/chibicc/chibicc.com
CHIBICC2 = o/$(MODE)/third_party/chibicc/chibicc2.com
CHIBICC_FLAGS = \
-fno-common \
-include libc/integral/normalize.inc \
@ -134,11 +134,11 @@ o/$(MODE)/third_party/chibicc/chibicc.o: \
o/$(MODE)/third_party/chibicc/chibicc.chibicc.o: \
CHIBICC_FLAGS += $(THIRD_PARTY_CHIBICC_DEFINES)
o/$(MODE)/%.chibicc.o: %.s o/$(MODE)/third_party/chibicc/chibicc.com.dbg
o/$(MODE)/%.chibicc.o: %.s $(CHIBICC)
@$(COMPILE) -ACHIBICC -T$@ $(CHIBICC) $(CHIBICC_FLAGS) -c -o $@ $<
o/$(MODE)/%.chibicc.o: %.c o/$(MODE)/third_party/chibicc/chibicc.com.dbg
o/$(MODE)/%.chibicc.o: %.c $(CHIBICC)
@$(COMPILE) -ACHIBICC -T$@ $(CHIBICC) $(CHIBICC_FLAGS) -c -o $@ $<
o/$(MODE)/%.chibicc2.o: %.c o/$(MODE)/third_party/chibicc/chibicc2.com.dbg
o/$(MODE)/%.chibicc2.o: %.c $(CHIBICC2)
@$(COMPILE) -ACHIBICC2 -T$@ $(CHIBICC2) $(CHIBICC_FLAGS) -c -o $@ $<
THIRD_PARTY_CHIBICC_LIBS = $(foreach x,$(THIRD_PARTY_CHIBICC_ARTIFACTS),$($(x)))