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ANDROID: KVM: arm64: Add Ftrace trampolines for pKVM hyp

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In preparation for supporting Ftrace in the pKVM hypervisor, add two
trampolines. The first one intends to trace function entries. It saves
the caller states before jumping into __hyp_ftrace_trace(). It is
expected from the latter to return the link register.

That LR can then either be the orignal caller parent, or our second
trampoline __hyp_ftrace_ret_tramp. This trampoline is calling
__hyp_ftrace_ret_trace() which can trace function returns and must
restore the original LR value.

Bug: 357781595
Change-Id: I9327d15d8c69ff94c9dbff2806a145de29af308b
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
This commit is contained in:
Vincent Donnefort
2024-10-01 14:17:09 +01:00
parent e77aff6717
commit e028749e5a
1 changed files with 45 additions and 0 deletions
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arch/arm64/kvm/hyp/hyp-entry.S
+45
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@@ -262,3 +262,48 @@ SYM_CODE_START(__bp_harden_hyp_vecs)
1: .org __bp_harden_hyp_vecs + __BP_HARDEN_HYP_VECS_SZ
.org 1b
SYM_CODE_END(__bp_harden_hyp_vecs)
#if defined(__KVM_NVHE_HYPERVISOR__) && defined(CONFIG_PROTECTED_NVHE_FTRACE)
SYM_FUNC_START(__hyp_ftrace_tramp)
stp x0, x1, [sp, #-16]!
stp x2, x3, [sp, #-16]!
stp x4, x5, [sp, #-16]!
stp x6, x7, [sp, #-16]!
stp x8, x29, [sp, #-16]! // x8, FP
stp x30, xzr, [sp, #-16]! // LR, ALIGN(16)
sub x0, x30, #AARCH64_INSN_SIZE // unsigned long ip
mov x1, x9 // unsigned long parent_ip
mov x2, x10 // unsigned long offset_idx
bl __hyp_ftrace_trace
mov x30, x0 // LR = __hyp_ftrace_trace();
ldp x9, xzr, [sp], #16
ldp x8, x29, [sp], #16
ldp x6, x7, [sp], #16
ldp x4, x5, [sp], #16
ldp x2, x3, [sp], #16
ldp x0, x1, [sp], #16
ret x9
SYM_FUNC_END(__hyp_ftrace_tramp)
SYM_FUNC_START(__hyp_ftrace_ret_tramp)
stp x0, x1, [sp, #-16]!
stp x2, x3, [sp, #-16]!
stp x4, x5, [sp, #-16]!
stp x6, x7, [sp, #-16]!
stp x8, x29, [sp, #-16]! // x8, FP
bl __hyp_ftrace_ret_trace
mov x30, x0
ldp x8, x29, [sp], #16 // x8, FP
ldp x6, x7, [sp], #16
ldp x4, x5, [sp], #16
ldp x2, x3, [sp], #16
ldp x0, x1, [sp], #16
ret
SYM_FUNC_END(__hyp_ftrace_ret_tramp)
#endif