[PATCH v2 06/27] x86/entry/64: Adapt assembly for PIE support
From: Thomas Garnier via Virtualization <hidden>
Date: 2018-03-13 20:59:24
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 entry code · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski
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 extended the KASLR randomization range below the -2G memory limit. Signed-off-by: Thomas Garnier <redacted> --- arch/x86/entry/entry_64.S | 16 ++++++++++------ arch/x86/kernel/relocate_kernel_64.S | 8 +++----- 2 files changed, 13 insertions(+), 11 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index bd53c57617e6..c53123468364 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)
@@ -1275,7 +1275,8 @@ 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 /*
@@ -1480,10 +1481,10 @@ 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:
@@ -1537,7 +1538,8 @@ 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
@@ -1576,7 +1578,9 @@ first_nmi: addq $8, (%rsp) /* Fix up RSP */ pushfq /* RFLAGS */ pushq $__KERNEL_CS /* CS */ - pushq $1f /* RIP */ + pushq %rax /* Support Position Independent Code */ + leaq 1f(%rip), %rax /* RIP */ + xchgq %rax, (%rsp) /* Restore RAX, put 1f */ 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
--
2.16.2.660.g709887971b-goog