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ArmPkg/ArmMmuLib: Disable and re-enable MMU only when needed

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When updating a page table descriptor in a way that requires break
before make, we temporarily disable the MMU to ensure that we don't
unmap the memory region that the code itself is executing from.

However, this is a condition we can check in a straight-forward manner,
and if the regions are disjoint, we don't have to bother with the MMU
controls, and we can just perform an ordinary break before make.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>
This commit is contained in:
Ard Biesheuvel
2022-09-24 18:26:19 +02:00
committed by mergify[bot]
parent ab644cfac5
commit 0487cac09f
3 changed files with 123 additions and 29 deletions
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43
ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S
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@@ -12,6 +12,14 @@
.macro __replace_entry, el
// check whether we should disable the MMU
cbz x3, .L1_\@
// clean and invalidate first so that we don't clobber
// adjacent entries that are dirty in the caches
dc civac, x0
dsb nsh
// disable the MMU
mrs x8, sctlr_el\el
bic x9, x8, #CTRL_M_BIT
@@ -38,8 +46,33 @@
// re-enable the MMU
msr sctlr_el\el, x8
isb
b .L2_\@
.L1_\@:
// write invalid entry
str xzr, [x0]
dsb nshst
// flush translations for the target address from the TLBs
lsr x2, x2, #12
.if \el == 1
tlbi vaae1, x2
.else
tlbi vae\el, x2
.endif
dsb nsh
// write updated entry
str x1, [x0]
dsb nshst
.L2_\@:
.endm
// Align this routine to a log2 upper bound of its size, so that it is
// guaranteed not to cross a page or block boundary.
.balign 0x200
//VOID
//ArmReplaceLiveTranslationEntry (
// IN UINT64 *Entry,
@@ -53,12 +86,7 @@ ASM_FUNC(ArmReplaceLiveTranslationEntry)
msr daifset, #0xf
isb
// clean and invalidate first so that we don't clobber
// adjacent entries that are dirty in the caches
dc civac, x0
dsb nsh
EL1_OR_EL2_OR_EL3(x3)
EL1_OR_EL2_OR_EL3(x5)
1:__replace_entry 1
b 4f
2:__replace_entry 2
@@ -72,3 +100,6 @@ ASM_GLOBAL ASM_PFX(ArmReplaceLiveTranslationEntrySize)
ASM_PFX(ArmReplaceLiveTranslationEntrySize):
.long . - ArmReplaceLiveTranslationEntry
// Double check that we did not overrun the assumed maximum size
.org ArmReplaceLiveTranslationEntry + 0x200