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mldr: Don't overwrite existing memory when loading files
Also, don't worry about failures mapping PAGEZERO; sane systems
already map out enough pages to reserve the area around `NULL`
as invalid memory.
This should fix some crashes that some users were getting (with mldr overwriting itself).
+11
-5
+11
-5
src/startup/mldr/loader.c
+11
-5
src/startup/mldr/loader.c
···
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addr += slide;
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// Some segments' filesize != vmsize, thus this mprotect().
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-
rv = mmap((void*)addr, seg->vmsize, useprot, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
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+
rv = mmap((void*)addr, seg->vmsize, useprot, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 0);
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if (rv == (void*)MAP_FAILED)
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{
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-
fprintf(stderr, "Cannot mmap segment %s at %p: %s\n", seg->segname, (void*)(uintptr_t)seg->vmaddr, strerror(errno));
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-
exit(1);
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+
if (addr == 0 && useprot == 0) {
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+
// this is the PAGEZERO segment;
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+
// if we can't map it, assume everything is fine and the system has already made that area inaccessible
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+
rv = 0;
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+
} else {
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+
fprintf(stderr, "Cannot mmap segment %s at %p: %s\n", seg->segname, (void*)(uintptr_t)seg->vmaddr, strerror(errno));
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+
exit(1);
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+
}
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}
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}
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else
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{
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size_t size = seg->vmsize - seg->filesize;
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rv = mmap((void*) PAGE_ALIGN(seg->vmaddr + seg->vmsize - size), PAGE_ROUNDUP(size), useprot,
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-
MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
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+
MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 0);
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if (rv == (void*)MAP_FAILED)
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{
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fprintf(stderr, "Cannot mmap segment %s at %p: %s\n", seg->segname, (void*)(uintptr_t)seg->vmaddr, strerror(errno));
···
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{
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unsigned long addr = seg->vmaddr + slide;
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rv = mmap((void*)addr, seg->filesize, useprot,
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-
MAP_FIXED | MAP_PRIVATE, fd, seg->fileoff + fat_offset);
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+
MAP_FIXED_NOREPLACE | MAP_PRIVATE, fd, seg->fileoff + fat_offset);
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if (rv == (void*)MAP_FAILED)
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{
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fprintf(stderr, "Cannot mmap segment %s at %p: %s\n", seg->segname, (void*)(uintptr_t)seg->vmaddr, strerror(errno));