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[PATCH 18/24] linux-user: Rewrite mmap_reserve
From: |
Richard Henderson |
Subject: |
[PATCH 18/24] linux-user: Rewrite mmap_reserve |
Date: |
Fri, 30 Jun 2023 15:21:53 +0200 |
Use 'last' variables instead of 'end' variables; be careful
about avoiding overflow. Assert that the mmap succeeded.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
linux-user/mmap.c | 68 +++++++++++++++++++++++++++++------------------
1 file changed, 42 insertions(+), 26 deletions(-)
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 67a117823f..6b030dac42 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -722,47 +722,63 @@ fail:
return -1;
}
-static void mmap_reserve(abi_ulong start, abi_ulong size)
+static void mmap_reserve(abi_ulong start, abi_ulong len)
{
abi_ulong real_start;
- abi_ulong real_end;
- abi_ulong addr;
- abi_ulong end;
+ abi_ulong real_last;
+ abi_ulong real_len;
+ abi_ulong last;
+ abi_ulong a;
+ void *host_start, *ptr;
int prot;
+ last = start + len - 1;
real_start = start & qemu_host_page_mask;
- real_end = HOST_PAGE_ALIGN(start + size);
- end = start + size;
- if (start > real_start) {
- /* handle host page containing start */
+ real_last = HOST_PAGE_ALIGN(last) - 1;
+
+ /*
+ * If guest pages remain on the first or last host pages,
+ * adjust the deallocation to retain those guest pages.
+ * The single page special case is required for the last page,
+ * lest real_start overflow to zero.
+ */
+ if (real_last - real_start < qemu_host_page_size) {
prot = 0;
- for (addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
- prot |= page_get_flags(addr);
+ for (a = real_start; a < start; a += TARGET_PAGE_SIZE) {
+ prot |= page_get_flags(a);
}
- if (real_end == real_start + qemu_host_page_size) {
- for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
- prot |= page_get_flags(addr);
- }
- end = real_end;
+ for (a = last; a < real_last; a += TARGET_PAGE_SIZE) {
+ prot |= page_get_flags(a + 1);
+ }
+ if (prot != 0) {
+ return;
+ }
+ } else {
+ for (prot = 0, a = real_start; a < start; a += TARGET_PAGE_SIZE) {
+ prot |= page_get_flags(a);
}
if (prot != 0) {
real_start += qemu_host_page_size;
}
- }
- if (end < real_end) {
- prot = 0;
- for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
- prot |= page_get_flags(addr);
+
+ for (prot = 0, a = last; a < real_last; a += TARGET_PAGE_SIZE) {
+ prot |= page_get_flags(a + 1);
}
if (prot != 0) {
- real_end -= qemu_host_page_size;
+ real_last -= qemu_host_page_size;
+ }
+
+ if (real_last < real_start) {
+ return;
}
}
- if (real_start != real_end) {
- mmap(g2h_untagged(real_start), real_end - real_start, PROT_NONE,
- MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,
- -1, 0);
- }
+
+ real_len = real_last - real_start + 1;
+ host_start = g2h_untagged(real_start);
+
+ ptr = mmap(host_start, real_len, PROT_NONE,
+ MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, -1, 0);
+ assert(ptr == host_start);
}
int target_munmap(abi_ulong start, abi_ulong len)
--
2.34.1
- [PATCH 07/24] accel/tcg: Introduce page_check_range_empty, (continued)
- [PATCH 07/24] accel/tcg: Introduce page_check_range_empty, Richard Henderson, 2023/06/30
- [PATCH 03/24] linux-user/strace: Expand struct flags to hold a mask, Richard Henderson, 2023/06/30
- [PATCH 05/24] linux-user: Split TARGET_PROT_* out of syscall_defs.h, Richard Henderson, 2023/06/30
- [PATCH 08/24] bsd-user: Use page_check_range_empty for MAP_EXCL, Richard Henderson, 2023/06/30
- [PATCH 11/24] linux-user: Widen target_mmap offset argument to off_t, Richard Henderson, 2023/06/30
- [PATCH 12/24] linux-user: Rewrite target_mprotect, Richard Henderson, 2023/06/30
- [PATCH 09/24] linux-user: Implement MAP_FIXED_NOREPLACE, Richard Henderson, 2023/06/30
- [PATCH 10/24] linux-user: Split out target_to_host_prot, Richard Henderson, 2023/06/30
- [PATCH 14/24] accel/tcg: Introduce page_find_range_empty, Richard Henderson, 2023/06/30
- [PATCH 13/24] linux-user: Rewrite mmap_frag, Richard Henderson, 2023/06/30
- [PATCH 18/24] linux-user: Rewrite mmap_reserve,
Richard Henderson <=
- [PATCH 15/24] bsd-user: Use page_find_range_empty for mmap_find_vma_reserved, Richard Henderson, 2023/06/30
- [PATCH 16/24] linux-user: Use page_find_range_empty for mmap_find_vma_reserved, Richard Henderson, 2023/06/30
- [PATCH 17/24] linux-user: Use 'last' instead of 'end' in target_mmap, Richard Henderson, 2023/06/30
- [PATCH 20/24] linux-user: Simplify target_munmap, Richard Henderson, 2023/06/30
- [PATCH 21/24] accel/tcg: Accept more page flags in page_check_range, Richard Henderson, 2023/06/30
- [PATCH 19/24] linux-user: Rename mmap_reserve to mmap_reserve_or_unmap, Richard Henderson, 2023/06/30
- [PATCH 22/24] accel/tcg: Return bool from page_check_range, Richard Henderson, 2023/06/30
- [PATCH 23/24] linux-user: Remove can_passthrough_madvise, Richard Henderson, 2023/06/30
- [PATCH 24/24] linux-user: Simplify target_madvise, Richard Henderson, 2023/06/30