* Thomas Garnier <thgarnie@xxxxxxxxxx> wrote: > 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 <thgarnie@xxxxxxxxxx> > --- > arch/x86/entry/entry_64.S | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 49167258d587..15bd5530d2ae 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -194,12 +194,15 @@ entry_SYSCALL_64_fastpath: > ja 1f /* return -ENOSYS (already in pt_regs->ax) */ > movq %r10, %rcx > > + /* Ensures the call is position independent */ > + leaq sys_call_table(%rip), %r11 > + > /* > * This call instruction is handled specially in stub_ptregs_64. > * It might end up jumping to the slow path. If it jumps, RAX > * and all argument registers are clobbered. > */ > - call *sys_call_table(, %rax, 8) > + call *(%r11, %rax, 8) > .Lentry_SYSCALL_64_after_fastpath_call: > > movq %rax, RAX(%rsp) > @@ -334,7 +337,8 @@ ENTRY(stub_ptregs_64) > * RAX stores a pointer to the C function implementing the syscall. > * IRQs are on. > */ > - cmpq $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp) > + leaq .Lentry_SYSCALL_64_after_fastpath_call(%rip), %r11 > + cmpq %r11, (%rsp) > jne 1f > > /* > @@ -1172,7 +1176,8 @@ 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 > > /* > @@ -1383,10 +1388,10 @@ 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: > @@ -1440,7 +1445,8 @@ 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 > @@ -1479,7 +1485,9 @@ 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 */ > INTERRUPT_RETURN /* continues at repeat_nmi below */ > UNWIND_HINT_IRET_REGS This patch seems to add extra overhead to the syscall fast-path even when PIE is disabled, right? Thanks, Ingo _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
