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[v3,30/30] arm64: efi/libstub: enter with the MMU on if executing in place

Message ID 20220411094824.4176877-31-ardb@kernel.org
State New
Headers show
Series arm64: support WXN and entry with MMU enabled | expand

Commit Message

Ard Biesheuvel April 11, 2022, 9:48 a.m. UTC 
If the kernel image has not been moved from the place where it was
loaded by the firmware, just call the kernel entrypoint directly, and
keep the MMU and caches enabled. This removes the need for any cache
invalidation in the entry path.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/efi-entry.S | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
index 61a87fa1c305..0da0b373cf32 100644
--- a/arch/arm64/kernel/efi-entry.S
+++ b/arch/arm64/kernel/efi-entry.S
@@ -23,6 +23,10 @@  SYM_CODE_START(efi_enter_kernel)
 	add	x19, x0, x2		// relocated Image entrypoint
 	mov	x20, x1			// DTB address
 
+	adrp	x3, _text		// just call the entrypoint
+	cmp	x0, x3			// directly if the image was
+	b.eq	2f			// not moved around in memory
+
 	/*
 	 * Clean the copied Image to the PoC, and ensure it is not shadowed by
 	 * stale icache entries from before relocation.