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linux-user: Use MAP_FIXED_NOREPLACE for do_brk()

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MAP_FIXED_NOREPLACE can ensure the mapped address is fixed without
concerning that the new mapping overwrites something else.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-Id: <20230802071754.14876-5-akihiko.odaki@daynix.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Akihiko Odaki 2023-08-02 16:17:50 +09:00 committed by Richard Henderson
parent c6cc059eca
commit e69e032d1a
1 changed files with 2 additions and 13 deletions
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15
linux-user/syscall.c
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@ -854,17 +854,12 @@ abi_long do_brk(abi_ulong brk_val)
return target_brk;
}
/* We need to allocate more memory after the brk... Note that
* we don't use MAP_FIXED because that will map over the top of
* any existing mapping (like the one with the host libc or qemu
* itself); instead we treat "mapped but at wrong address" as
* a failure and unmap again.
*/
if (new_host_brk_page > brk_page) {
new_alloc_size = new_host_brk_page - brk_page;
mapped_addr = target_mmap(brk_page, new_alloc_size,
PROT_READ | PROT_WRITE,
MAP_ANON | MAP_PRIVATE, -1, 0);
MAP_FIXED_NOREPLACE | MAP_ANON | MAP_PRIVATE,
-1, 0);
} else {
new_alloc_size = 0;
mapped_addr = brk_page;
@ -883,12 +878,6 @@ abi_long do_brk(abi_ulong brk_val)
target_brk = brk_val;
brk_page = new_host_brk_page;
return target_brk;
} else if (mapped_addr != -1) {
/* Mapped but at wrong address, meaning there wasn't actually
* enough space for this brk.
*/
target_munmap(mapped_addr, new_alloc_size);
mapped_addr = -1;
}
#if defined(TARGET_ALPHA)