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in early stage ldso before __dls2b, call mprotect with __syscall

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if LTO is enabled, gcc hoists the call to ___errno_location outside the
loop even though the access to errno is gated behind head != &ldso
because ___errno_location is marked __attribute__((const)). this causes
the program to crash because TLS is not yet initialized when called from
__dls2. this is also possible if LTO is not enabled; even though gcc 11
doesn't do it, it is still wrong to use errno here.

since the start and end are already aligned, we can simply call
__syscall instead of using global errno.

Fixes: e13a2b8953 ("implement PT_GNU_RELRO support")
This commit is contained in:
Alex Xu (Hello71)
2022-07-02 16:12:04 -04:00
committed by Rich Felker
parent a23a3da29b
commit 63c67053a3
1 changed files with 8 additions and 6 deletions
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ldso/dynlink.c
+8 -6
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@@ -1356,12 +1356,14 @@ static void reloc_all(struct dso *p)
do_relocs(p, laddr(p, dyn[DT_REL]), dyn[DT_RELSZ], 2);
do_relocs(p, laddr(p, dyn[DT_RELA]), dyn[DT_RELASZ], 3);
if (head != &ldso && p->relro_start != p->relro_end &&
mprotect(laddr(p, p->relro_start), p->relro_end-p->relro_start, PROT_READ)
&& errno != ENOSYS) {
error("Error relocating %s: RELRO protection failed: %m",
p->name);
if (runtime) longjmp(*rtld_fail, 1);
if (head != &ldso && p->relro_start != p->relro_end) {
long ret = __syscall(SYS_mprotect, laddr(p, p->relro_start),
p->relro_end-p->relro_start, PROT_READ);
if (ret != 0 && ret != -ENOSYS) {
error("Error relocating %s: RELRO protection failed: %m",
p->name);
if (runtime) longjmp(*rtld_fail, 1);
}
}
p->relocated = 1;