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[PATCH v5 02/31] linux-user: Introduce PAGE_ANON
From: |
Richard Henderson |
Subject: |
[PATCH v5 02/31] linux-user: Introduce PAGE_ANON |
Date: |
Wed, 3 Feb 2021 08:59:41 -1000 |
Record whether the backing page is anonymous, or if it has file
backing. This will allow us to get close to the Linux AArch64
ABI for MTE, which allows tag memory only on ram-backed VMAs.
The real ABI allows tag memory on files, when those files are
on ram-backed filesystems, such as tmpfs. We will not be able
to implement that in QEMU linux-user.
Thankfully, anonymous memory for malloc arenas is the primary
consumer of this feature, so this restricted version should
still be of use.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
include/exec/cpu-all.h | 2 ++
linux-user/mmap.c | 3 +++
2 files changed, 5 insertions(+)
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 99a09ee137..c23c77589b 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -275,6 +275,8 @@ extern intptr_t qemu_host_page_mask;
#define PAGE_WRITE_INV 0x0020
/* For use with page_set_flags: page is being replaced; target_data cleared. */
#define PAGE_RESET 0x0040
+/* For linux-user, indicates that the page is MAP_ANON. */
+#define PAGE_ANON 0x0080
#if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY)
/* FIXME: Code that sets/uses this is broken and needs to go away. */
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index c693505b60..7fb4c628e1 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -599,6 +599,9 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int
target_prot,
}
}
the_end1:
+ if (flags & MAP_ANONYMOUS) {
+ page_flags |= PAGE_ANON;
+ }
page_flags |= PAGE_RESET;
page_set_flags(start, start + len, page_flags);
the_end:
--
2.25.1
- [PATCH v5 00/31] target-arm: Implement ARMv8.5-MemTag, user mode, Richard Henderson, 2021/02/03
- [PATCH v5 05/31] exec: Improve types for guest_addr_valid, Richard Henderson, 2021/02/03
- [PATCH v5 07/31] linux-user: Tidy VERIFY_READ/VERIFY_WRITE, Richard Henderson, 2021/02/03
- [PATCH v5 10/31] linux-user: Fix guest_addr_valid vs reserved_va, Richard Henderson, 2021/02/03
- [PATCH v5 11/31] exec: Introduce cpu_untagged_addr, Richard Henderson, 2021/02/03
- [PATCH v5 12/31] exec: Use cpu_untagged_addr in g2h; split out g2h_untagged, Richard Henderson, 2021/02/03