Implement missing bits to support lazy binding. Note that the code

deliberately does not save the floating-point argument registers
before calling _dl_bind().  Doing so would force an FPU context switch
upon every function call through the PLT.  But since we compile ld.so
with -march=armv8-a+nofp+nosimd this is safe since nothing in the _dl_bind()
codepath uses he FPU registers.

ok guenther@, drahn@

diff --git a/libexec/ld.so/aarch64/ldasm.S b/libexec/ld.so/aarch64/ldasm.S
index f60480d..890936c 100644 (file)
--- a/libexec/ld.so/aarch64/ldasm.S
+++ b/libexec/ld.so/aarch64/ldasm.S
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ldasm.S,v 1.4 2017/08/27 21:59:51 deraadt Exp $ */
+/*     $OpenBSD: ldasm.S,v 1.5 2017/12/21 00:32:55 kettenis Exp $ */
 
 /*
  * Copyright (c) 2016 Dale Rahn
@@ -65,50 +65,44 @@ ENTRY(_dl_start)
 
 ENTRY(_dl_bind_start)
        /*
-        * ip is pointer to got entry for this relocation
-        * lr is pointer to pltgot[2], which is entry -1 of got plt reloc.
-        * return address is on stack
+        * x16 is pointer to pltgot[2]
+        * x17 is available as scratch register
+        * return address and pointer to pltgot entry for this
+        * relocation are on the stack
         */
-       stp     x29, x30, [sp, #-160]!
-       stp      x0,  x1, [sp,#16]
-       stp      x2,  x3, [sp,#32]
-       stp      x4,  x5, [sp,#48]
-       stp      x6,  x7, [sp,#64]
-       stp      x8,  x9, [sp,#80]
-       stp     x10, x11, [sp,#96]
-       stp     x12, x13, [sp,#112]
-       stp     x14, x15, [sp,#128]
-       str     x18,      [sp,#144]
-
-       mov     x1, x16         // reladdr
-
-
-       ldp      x0,  x1, [sp,#16]
-       ldp      x2,  x3, [sp,#32]
-       ldp      x4,  x5, [sp,#48]
-       ldp      x6,  x7, [sp,#64]
-       ldp      x8,  x9, [sp,#80]
-       ldp     x10, x11, [sp,#96]
-       ldp     x12, x13, [sp,#112]
-       ldp     x14, x15, [sp,#128]
-       ldr     x18,      [sp,#144]
-       ldp     x29, x30, [sp], #-160
-       br x16
-
-
-#if 0
-       stmdb   sp!, {r0-r4,sl,fp}
-
-       sub     r1, ip, lr              /* r1 = 4 * (n + 1) */
-       sub     r1, r1, #4              /* r1 = 4 * n */
-       mov     r1, r1, lsr #2          /* r1 = n */
-
-       ldr     r0, [lr, #-4]
+       mov x17, sp
+
+       // save parameter/result registers
+       stp     x0, x1, [sp, #-16]!
+       stp     x2, x3, [sp, #-16]!
+       stp     x4, x5, [sp, #-16]!
+       stp     x6, x7, [sp, #-16]!
+       stp     x8, xzr, [sp, #-16]!
+
+       /*
+        * no need to save v0-v9 as ld.so is compiled with
+        * -march=armv8-a+nofp+nosimd and therefore doesn't touch the
+        * SIMD and Floating-Point registers
+        */
+
+       ldr     x0, [x16, #-8]          // object
+       ldr     x2, [x17]
+       sub     x1, x2, x16
+       sub     x1, x1, #8
+       lsr     x1, x1, #3              // relidx
        bl      _dl_bind
-       mov     ip, r0
-       ldmia   sp!, {r0-r4,sl,fp,lr}
-       mov     pc, ip
-#endif
+       mov     x17, x0
+
+       // restore parameter/result registers
+       ldp     x8, xzr, [sp], #16
+       ldp     x6, x7, [sp], #16
+       ldp     x4, x5, [sp], #16
+       ldp     x2, x3, [sp], #16
+       ldp     x0, x1, [sp], #16
+
+       // restore LR saved by PLT stub 
+       ldp     xzr, x30, [sp], #16
+       br      x17
 
 ENTRY(_rtld_tlsdesc)
        ldr     x0, [x0, #8]

diff --git a/libexec/ld.so/aarch64/rtld_machine.c b/libexec/ld.so/aarch64/rtld_machine.c
index 2316b0a..c7c6663 100644 (file)
--- a/libexec/ld.so/aarch64/rtld_machine.c
+++ b/libexec/ld.so/aarch64/rtld_machine.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: rtld_machine.c,v 1.4 2017/10/24 20:35:54 guenther Exp $ */
+/*     $OpenBSD: rtld_machine.c,v 1.5 2017/12/21 00:32:55 kettenis Exp $ */
 
 /*
  * Copyright (c) 2004 Dale Rahn
@@ -294,8 +294,6 @@ _dl_md_reloc_got(elf_object_t *object, int lazy)
        if (object->traced)
                lazy = 1;
 
-       lazy = 0; // until support is written.
-
        if (!lazy) {
                fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ);
        } else {