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linux-user/aarch64: Do not clear PROT_MTE on mprotect

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The documentation for PROT_MTE says that it cannot be cleared
by mprotect.  Further, the implementation of the VM_ARCH_CLEAR bit,
contains PROT_BTI confiming that bit should be cleared.

Introduce PAGE_TARGET_STICKY to allow target/arch/cpu.h to control
which bits may be reset during page_set_flags.  This is sort of the
opposite of VM_ARCH_CLEAR, but works better with qemu's PAGE_* bits
that are separate from PROT_* bits.

Reported-by: Vitaly Buka <vitalybuka@google.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220711031420.17820-1-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Richard Henderson 2022-07-11 08:44:20 +05:30 committed by Peter Maydell
parent 6a775fd6e0
commit 7f2cf760fe
2 changed files with 16 additions and 4 deletions
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13
accel/tcg/translate-all.c
View File

@ -2256,6 +2256,15 @@ int page_get_flags(target_ulong address)
return p->flags;
}
/*
* Allow the target to decide if PAGE_TARGET_[12] may be reset.
* By default, they are not kept.
*/
#ifndef PAGE_TARGET_STICKY
#define PAGE_TARGET_STICKY 0
#endif
#define PAGE_STICKY (PAGE_ANON | PAGE_TARGET_STICKY)
/* Modify the flags of a page and invalidate the code if necessary.
The flag PAGE_WRITE_ORG is positioned automatically depending
on PAGE_WRITE. The mmap_lock should already be held. */
@ -2299,8 +2308,8 @@ void page_set_flags(target_ulong start, target_ulong end, int flags)
p->target_data = NULL;
p->flags = flags;
} else {
/* Using mprotect on a page does not change MAP_ANON. */
p->flags = (p->flags & PAGE_ANON) | flags;
/* Using mprotect on a page does not change sticky bits. */
p->flags = (p->flags & PAGE_STICKY) | flags;
}
}
}

7
target/arm/cpu.h
View File

@ -3392,9 +3392,12 @@ static inline MemTxAttrs *typecheck_memtxattrs(MemTxAttrs *x)
/*
* AArch64 usage of the PAGE_TARGET_* bits for linux-user.
* Note that with the Linux kernel, PROT_MTE may not be cleared by mprotect
* mprotect but PROT_BTI may be cleared. C.f. the kernel's VM_ARCH_CLEAR.
*/
#define PAGE_BTI PAGE_TARGET_1
#define PAGE_MTE PAGE_TARGET_2
#define PAGE_BTI PAGE_TARGET_1
#define PAGE_MTE PAGE_TARGET_2
#define PAGE_TARGET_STICKY PAGE_MTE
#ifdef TARGET_TAGGED_ADDRESSES
/**