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kvm/arm64: enable guest mmu from the host

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Right now, the start function is executed with the disabled MMU and it means
every access the PA is equal to the MVA [1]. This is known as a flat address
mapping.

By coincidence, the code segment is mapped in lower addresses and we have the
flat address mapping for it. But it isn't the case if we set buildmode=pie to
enable ASLR.

[1] https://developer.arm.com/documentation/ddi0406/b/System-Level-Architecture/Virtual-Memory-System-Architecture--VMSA-/Memory-access-sequence/Enabling-and-disabling-the-MMU

PiperOrigin-RevId: 523745143
This commit is contained in:
Andrei Vagin
2023-04-12 10:53:24 -07:00
committed by gVisor bot
parent 3b537e7f0c
commit 876908e5e0
3 changed files with 49 additions and 57 deletions
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pkg/ring0/entry_arm64.s
-46
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@@ -126,22 +126,6 @@
#define FPEN_ENABLE (FPEN_NOTRAP << FPEN_SHIFT)
// sctlr_el1: system control register el1.
#define SCTLR_M 1 << 0
#define SCTLR_C 1 << 2
#define SCTLR_I 1 << 12
#define SCTLR_DZE 1 << 14
#define SCTLR_UCT 1 << 15
#define SCTLR_UCI 1 << 26
#define SCTLR_EL1_DEFAULT (SCTLR_M | SCTLR_C | SCTLR_I | SCTLR_UCT | SCTLR_UCI | SCTLR_DZE)
// cntkctl_el1: counter-timer kernel control register el1.
#define CNTKCTL_EL0PCTEN 1 << 0
#define CNTKCTL_EL0VCTEN 1 << 1
#define CNTKCTL_EL1_DEFAULT (CNTKCTL_EL0PCTEN | CNTKCTL_EL0VCTEN)
// Saves a register set.
//
// This is a macro because it may need to executed in contents where a stack is
@@ -604,39 +588,9 @@ TEXT ·kernelExitToEl1(SB),NOSPLIT,$0
ERET()
// start is the CPU entrypoint.
TEXT ·start(SB),NOSPLIT,$0
// Init.
WORD $0xd508871f // __tlbi(vmalle1)
DSB $7 // dsb(nsh)
MOVD $1<<12, R1 // Reset mdscr_el1 and disable
MSR R1, MDSCR_EL1 // access to the DCC from EL0
ISB $15
MRS TTBR1_EL1, R1
MSR R1, TTBR0_EL1
ISB $15
MOVD $CNTKCTL_EL1_DEFAULT, R1
MSR R1, CNTKCTL_EL1
MOVD R8, RSV_REG
ORR $0xffff000000000000, RSV_REG, RSV_REG
WORD $0xd518d092 //MSR R18, TPIDR_EL1
// Enable trap for accessing fpsimd.
MSR $0, CPACR_EL1
// Init.
MOVD $SCTLR_EL1_DEFAULT, R1 // re-enable the mmu.
MSR R1, SCTLR_EL1
ISB $15
WORD $0xd508751f // ic iallu
DSB $7 // dsb(nsh)
ISB $15
B ·kernelExitToEl1(SB)
// func AddrOfStart() uintptr