Change the assembly code to use only relative references of symbols for the kernel to be PIE compatible.
Position Independent Executable (PIE) support will allow to extend the KASLR randomization range 0xffffffff80000000. Signed-off-by: Thomas Garnier <[email protected]> --- arch/x86/entry/entry_64.S | 18 ++++++++++++------ arch/x86/kernel/relocate_kernel_64.S | 8 +++----- 2 files changed, 15 insertions(+), 11 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 3166b9674429..1cbf4c3616a8 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -191,7 +191,7 @@ ENTRY(entry_SYSCALL_64_trampoline) * spill RDI and restore it in a second-stage trampoline. */ pushq %rdi - movq $entry_SYSCALL_64_stage2, %rdi + movabsq $entry_SYSCALL_64_stage2, %rdi JMP_NOSPEC %rdi END(entry_SYSCALL_64_trampoline) @@ -1276,7 +1276,8 @@ ENTRY(error_entry) movl %ecx, %eax /* zero extend */ cmpq %rax, RIP+8(%rsp) je .Lbstep_iret - cmpq $.Lgs_change, RIP+8(%rsp) + leaq .Lgs_change(%rip), %rcx + cmpq %rcx, RIP+8(%rsp) jne .Lerror_entry_done /* @@ -1481,10 +1482,10 @@ ENTRY(nmi) * resume the outer NMI. */ - movq $repeat_nmi, %rdx + leaq repeat_nmi(%rip), %rdx cmpq 8(%rsp), %rdx ja 1f - movq $end_repeat_nmi, %rdx + leaq end_repeat_nmi(%rip), %rdx cmpq 8(%rsp), %rdx ja nested_nmi_out 1: @@ -1538,7 +1539,8 @@ nested_nmi: pushq %rdx pushfq pushq $__KERNEL_CS - pushq $repeat_nmi + leaq repeat_nmi(%rip), %rdx + pushq %rdx /* Put stack back */ addq $(6*8), %rsp @@ -1577,7 +1579,11 @@ first_nmi: addq $8, (%rsp) /* Fix up RSP */ pushfq /* RFLAGS */ pushq $__KERNEL_CS /* CS */ - pushq $1f /* RIP */ + pushq $0 /* Futur return address */ + pushq %rax /* Save RAX */ + leaq 1f(%rip), %rax /* RIP */ + movq %rax, 8(%rsp) /* Put 1f on return address */ + popq %rax /* Restore RAX */ iretq /* continues at repeat_nmi below */ UNWIND_HINT_IRET_REGS 1: diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index a7227dfe1a2b..0c0fc259a4e2 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -208,11 +208,9 @@ identity_mapped: movq %rax, %cr3 lea PAGE_SIZE(%r8), %rsp call swap_pages - jmp *virtual_mapped_addr(%rip) - - /* Absolute value for PIE support */ -virtual_mapped_addr: - .quad virtual_mapped + movabsq $virtual_mapped, %rax + pushq %rax + ret virtual_mapped: movq RSP(%r8), %rsp -- 2.17.0.921.gf22659ad46-goog
