From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Garnier Subject: [PATCH v6 05/27] x86/entry/64: Adapt assembly for PIE support Date: Thu, 31 Jan 2019 11:24:12 -0800 Message-Id: <20190131192533.34130-6-thgarnie@chromium.org> In-Reply-To: <20190131192533.34130-1-thgarnie@chromium.org> References: <20190131192533.34130-1-thgarnie@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: kernel-hardening@lists.openwall.com Cc: kristen@linux.intel.com, Thomas Garnier , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org List-ID: 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 below 0xffffffff80000000. Signed-off-by: Thomas Garnier --- arch/x86/entry/entry_64.S | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 1f0efdb7b629..16a93eb4c11f 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1269,7 +1269,8 @@ 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 /* @@ -1466,10 +1467,10 @@ 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: @@ -1523,7 +1524,8 @@ 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 @@ -1562,7 +1564,11 @@ 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: -- 2.20.1.495.gaa96b0ce6b-goog