iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

KVM: arm64: Use BTI for nvhe

Browse Source 
CONFIG_ARM64_BTI_KERNEL compiles the kernel to support ARMv8.5-BTI.
However, the nvhe code doesn't make use of it as it doesn't map any
pages with Guarded Page(GP) bit.

kvm pgtable code is modified to map executable pages with GP bit
if BTI is enabled for the kernel.

At hyp init, SCTLR_EL2.BT is set to 1 to match EL1 configuration
(SCTLR_EL1.BT1) set in bti_enable().

One difference between kernel and nvhe code, is that the kernel maps
.text with GP while nvhe maps all the executable pages, this makes
nvhe code need to deal with special initialization code coming from
other executable sections (.idmap.text).
For this we need to add bti instruction at the beginning of
__kvm_handle_stub_hvc as it can be called by  __host_hvc through
branch instruction(br) and unlike SYM_FUNC_START, SYM_CODE_START
doesn’t add bti instruction at the beginning, and it can’t be modified
to add it as it is used with vector tables.
Another solution which is more intrusive is to convert
__kvm_handle_stub_hvc to a function and inject “bti jc” instead of
“bti c” in SYM_FUNC_START

Signed-off-by: Mostafa Saleh <smostafa@google.com>
Link: https://lore.kernel.org/r/20230530150845.2856828-1-smostafa@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Mostafa Saleh 2023-05-30 15:08:45 +00:00 committed by Oliver Upton
parent c876c3f182
commit b53d4a2723
3 changed files with 19 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/include/asm/sysreg.h
View File

@ -558,6 +558,7 @@
(BIT(18)) | (BIT(22)) | (BIT(23)) | (BIT(28)) | \
(BIT(29)))
#define SCTLR_EL2_BT (BIT(36))
#ifdef CONFIG_CPU_BIG_ENDIAN
#define ENDIAN_SET_EL2 SCTLR_ELx_EE
#else

12
arch/arm64/kvm/hyp/nvhe/hyp-init.S
View File

@ -128,6 +128,13 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
SCTLR_ELx_ENDA | SCTLR_ELx_ENDB)
orr x0, x0, x1
alternative_else_nop_endif
#ifdef CONFIG_ARM64_BTI_KERNEL
alternative_if ARM64_BTI
orr x0, x0, #SCTLR_EL2_BT
alternative_else_nop_endif
#endif /* CONFIG_ARM64_BTI_KERNEL */
msr sctlr_el2, x0
isb
@ -196,6 +203,11 @@ SYM_CODE_START_LOCAL(__kvm_hyp_init_cpu)
SYM_CODE_END(__kvm_hyp_init_cpu)
SYM_CODE_START(__kvm_handle_stub_hvc)
/*
* __kvm_handle_stub_hvc called from __host_hvc through branch instruction(br) so
* we need bti j at beginning.
*/
bti j
cmp x0, #HVC_SOFT_RESTART
b.ne 1f

7
arch/arm64/kvm/hyp/pgtable.c
View File

@ -34,7 +34,7 @@
#define KVM_PTE_LEAF_ATTR_LO_S2_SH_IS 3
#define KVM_PTE_LEAF_ATTR_LO_S2_AF BIT(10)
#define KVM_PTE_LEAF_ATTR_HI GENMASK(63, 51)
#define KVM_PTE_LEAF_ATTR_HI GENMASK(63, 50)
#define KVM_PTE_LEAF_ATTR_HI_SW GENMASK(58, 55)
@ -42,6 +42,8 @@
#define KVM_PTE_LEAF_ATTR_HI_S2_XN BIT(54)
#define KVM_PTE_LEAF_ATTR_HI_S1_GP BIT(50)
#define KVM_PTE_LEAF_ATTR_S2_PERMS (KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \
KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \
KVM_PTE_LEAF_ATTR_HI_S2_XN)
@ -371,6 +373,9 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
if (device)
return -EINVAL;
if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
attr |= KVM_PTE_LEAF_ATTR_HI_S1_GP;
} else {
attr |= KVM_PTE_LEAF_ATTR_HI_S1_XN;
}