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[PULL 08/24] linux-user: Use MAP_FIXED_NOREPLACE for do_brk()
From: |
Richard Henderson |
Subject: |
[PULL 08/24] linux-user: Use MAP_FIXED_NOREPLACE for do_brk() |
Date: |
Sat, 5 Aug 2023 20:36:59 -0700 |
From: Akihiko Odaki <akihiko.odaki@daynix.com>
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>
[rth: Pass -1 as fd for MAP_ANON]
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
linux-user/syscall.c | 17 +++--------------
1 file changed, 3 insertions(+), 14 deletions(-)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index b9d2ec02f9..f64024273f 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -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, 0, 0);
+ PROT_READ | PROT_WRITE,
+ 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)
--
2.34.1
- [PULL 00/24] tcg + linux-user queue for 8.1-rc3, Richard Henderson, 2023/08/05
- [PULL 02/24] accel/tcg: Issue wider aligned i/o in do_{ld,st}_mmio_*, Richard Henderson, 2023/08/05
- [PULL 01/24] accel/tcg: Adjust parameters and locking with do_{ld, st}_mmio_*, Richard Henderson, 2023/08/05
- [PULL 03/24] accel/tcg: Do not issue misaligned i/o, Richard Henderson, 2023/08/05
- [PULL 04/24] gdbstub: use 0 ("any process") on packets with no PID, Richard Henderson, 2023/08/05
- [PULL 05/24] linux-user: Unset MAP_FIXED_NOREPLACE for host, Richard Henderson, 2023/08/05
- [PULL 06/24] linux-user: Fix MAP_FIXED_NOREPLACE on old kernels, Richard Henderson, 2023/08/05
- [PULL 07/24] linux-user: Do not call get_errno() in do_brk(), Richard Henderson, 2023/08/05
- [PULL 08/24] linux-user: Use MAP_FIXED_NOREPLACE for do_brk(),
Richard Henderson <=
- [PULL 09/24] linux-user: Do nothing if too small brk is specified, Richard Henderson, 2023/08/05
- [PULL 10/24] linux-user: Do not align brk with host page size, Richard Henderson, 2023/08/05
- [PULL 11/24] linux-user: Remove last_brk, Richard Henderson, 2023/08/05
- [PULL 12/24] bsd-user: Remove last_brk, Richard Henderson, 2023/08/05
- [PULL 13/24] linux-user: Adjust task_unmapped_base for reserved_va, Richard Henderson, 2023/08/05
- [PULL 14/24] linux-user: Define TASK_UNMAPPED_BASE in $guest/target_mman.h, Richard Henderson, 2023/08/05
- [PULL 15/24] linux-user: Define ELF_ET_DYN_BASE in $guest/target_mman.h, Richard Henderson, 2023/08/05
- [PULL 17/24] linux-user: Use elf_et_dyn_base for ET_DYN with interpreter, Richard Henderson, 2023/08/05
- [PULL 18/24] linux-user: Adjust initial brk when interpreter is close to executable, Richard Henderson, 2023/08/05
- [PULL 16/24] linux-user: Use MAP_FIXED_NOREPLACE for initial image mmap, Richard Henderson, 2023/08/05