[RFC PATCH 14/28] x86/rethook: Use RIP-relative reference for return address

[Ard Biesheuvel <ardb+git@xxxxxxxxxx>]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

Instead of pushing an immediate absolute address, which is incompatible
with PIE codegen or linking, use a LEA instruction to take the address
into a register.

Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 arch/x86/kernel/rethook.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
index 8a1c0111ae79..3b3c17ba3cd5 100644
--- a/arch/x86/kernel/rethook.c
+++ b/arch/x86/kernel/rethook.c
@@ -27,7 +27,8 @@ asm(
 #ifdef CONFIG_X86_64
        ANNOTATE_NOENDBR        /* This is only jumped from ret instruction */
        /* Push a fake return address to tell the unwinder it's a rethook. */
-       "       pushq $arch_rethook_trampoline\n"
+       "       leaq arch_rethook_trampoline(%rip), %rdi\n"
+       "       pushq %rdi\n"
        UNWIND_HINT_FUNC
        "       pushq $" __stringify(__KERNEL_DS) "\n"
        /* Save the 'sp - 16', this will be fixed later. */
-- 
2.46.0.792.g87dc391469-goog