Avoid writing the sandbox base address to memory in setjmp and memcpy

newlib/libc/machine/x86_64/setjmp.S

Index: newlib/libc/machine/x86_64/setjmp.S
diff --git a/newlib/libc/machine/x86_64/setjmp.S b/newlib/libc/machine/x86_64/setjmp.S
index b1d26adba38b905d3b269ded44f305b06de6b240..5f03c3e66bc4cb7c3f15370aa2129887551e4b2e 100644
--- a/newlib/libc/machine/x86_64/setjmp.S
+++ b/newlib/libc/machine/x86_64/setjmp.S
@@ -26,9 +26,10 @@ SYM (setjmp):
   movq    r12, %nacl:  8 (r15,rdi)
   movq    r13, %nacl: 16 (r15,rdi)
   movq    r14, %nacl: 24 (r15,rdi)
-  movq    (rsp), rax
-  movq    rax, %nacl: 32 (r15,rdi)
-  leaq    8 (rsp), rax
+  /* Avoid writing the top 32 bits of rip, rbp, and rsp into memory. */
+  movl    (rsp), eax

[Mark Seaborn, 2015/02/11 02:23:45]

Note: shorter as:

popq %rax
movl    eax, %nacl: 32 (r15,rdi)
...
movl    esp, %nacl: 44 (r15,rdi)

(no leal needed)

[Derek Schuff, 2015/02/11 23:16:06]

Done.

+  movl    eax, %nacl: 32 (r15,rdi)
+  leal    8 (rsp), eax
   movl    ebp, %nacl: 40 (r15,rdi)
   movl    eax, %nacl: 44 (r15,rdi)
   movq    $0, rax
@@ -36,7 +37,11 @@ SYM (setjmp):
   nacljmp r11d, r15
 
 SYM (longjmp):
-  movq    rsi, rax        /* Return value */
+  movl    esi, eax        /* Return value */

[Mark Seaborn, 2015/02/11 02:23:45]

I'm not sure why you're changing this.  It looks like you're fixing this
longjmp() implementation to follow the standard.  If so, shouldn't that be a
separate change, with a test in the Scons build?

[Derek Schuff, 2015/02/11 18:19:11]

Yes, I noticed that it didn't conform and decided to fix that, but I'll make it
a separate CL.

+  /* if val is zero, we must return 1 -- otherwise return val */
+  movl    $1, ebx
+  testl   eax, eax
+  cmovz   ebx, eax
 
   naclrestbp %nacl: 40 (r15,rdi), r15