From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 10 Jun 2019 14:34:38 -0700 From: Kees Cook Subject: Re: [PATCH v7 05/12] x86/entry/64: Adapt assembly for PIE support Message-ID: <201906101433.C0DB679DD@keescook> References: <20190520231948.49693-1-thgarnie@chromium.org> <20190520231948.49693-6-thgarnie@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190520231948.49693-6-thgarnie@chromium.org> To: Thomas Garnier Cc: kernel-hardening@lists.openwall.com, 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: On Mon, May 20, 2019 at 04:19:30PM -0700, Thomas Garnier wrote: > From: Thomas Garnier > > 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 20e45d9b4e15..e99b3438aa9b 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1268,7 +1268,8 @@ 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 > > /* > @@ -1465,10 +1466,10 @@ 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: > @@ -1522,7 +1523,8 @@ 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 > @@ -1561,7 +1563,11 @@ first_nmi: > addq $8, (%rsp) /* Fix up RSP */ > pushfq /* RFLAGS */ > pushq $__KERNEL_CS /* CS */ > - pushq $1f /* RIP */ > + pushq $0 /* Futur return address */ typo: Future > + 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: Other than that: Reviewed-by: Kees Cook -- Kees Cook