NonSFI mode: Make tests/common/register_set.h PIC-friendly.

tests/common/register_set.h

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef NATIVE_CLIENT_TESTS_COMMON_REGISTER_SET_H_
 #define NATIVE_CLIENT_TESTS_COMMON_REGISTER_SET_H_
 
 #include "native_client/src/include/nacl/nacl_exception.h"
@@ skipping 222 matching lines @@
 
 # define REGS_SAVER_FUNC_NOPROTO(def_func, callee_func) \
     void callee_func(struct NaClSignalContext *regs); \
     __asm__( \
         ".pushsection .text, \"ax\", @progbits\n" \
         ".p2align 5\n" \
         ".global " #def_func "\n"\
         #def_func ":\n" \
         /* Push most of "struct NaClSignalContext" in reverse order. */ \
         "push $0\n"  /* Leave space for flags */ \
-        "push $" #def_func "\n"  /* Fill out prog_ctr with known value */ \
+        "push $0 \n" /* Leave space for prog_ctr */ \
         "push %edi\n" \
         "push %esi\n" \
         "push %ebp\n" \
         "push %esp\n" \
         "push %ebx\n" \
         "push %edx\n" \
         "push %ecx\n" \
         "push %eax\n" \
         /* Save flags. */ \
         SAVE_X86_FLAGS_INTO_REG("%eax") \
         "movl %eax, 0x24(%esp)\n" \
+        /* Obtain def_func from GOT to fill progg_ctr with known value. */ \

[Mark Seaborn, 2014/09/15 17:15:21]

Typo: "prog_ctr"

[Junichi Uekawa, 2014/09/16 01:37:53]

Done.

+        "call 0f\n" \
+        "0: popl %eax\n" \
+        "1: addl $_GLOBAL_OFFSET_TABLE_ + (1b - 0b), %eax\n" \
+        "movl " #def_func "@GOT(%eax), %eax\n" \
+        "movl %eax, 0x20(%esp)\n" \
         /* Adjust saved %esp value to account for preceding pushes. */ \
         "addl $5 * 4, 0x10(%esp)\n" \
         /* Save argument to callee_func() temporarily. */ \
         "mov %esp, %eax\n" \
         /* Align the stack pointer and leave space for an argument. */ \
         "pushl $0\n" \
         "and $~15, %esp\n" \
         /* Set argument to callee_func(). */ \
         "mov %eax, (%esp)\n" \
         "call " #callee_func "\n" \
@@ skipping 63 matching lines @@
         "push {r14}\n" \
         /* Save r0-r12 and sp; adjust sp for the pushes above */ \
         "add r14, sp, #0xc\n" \
         "push {r10-r12, r14}\n" \
         /* Push a dummy value for r9, which the tests need not compare */ \
         "mov r10, #0\n" \
         "push {r10}\n" \
         /* Save the rest of struct NaClSignalContext */ \
         "push {r0-r8}\n" \
         /* Now save a correct prog_ctr value */ \
-        "adr r0, " #def_func "\n" \

[Mark Seaborn, 2014/09/15 17:15:21]

Note that "adr" is already position independent.

The only problem with it is that it has limited range.  That doesn't seem to
have been a problem so far.  Changing this to the non-range-limited version
would be good, but maybe we can postpone it if it depends on a newer version of
LLVM?  (JF is working on updating PNaCl to use LLVM 3.5.)

[Junichi Uekawa, 2014/09/16 01:37:53]

I see, I missed the point that it was already position independent.
Sounds good.

-        "str r0, [sp, #0x3c]\n" \
+        "ldr r2, 11f\n" \
+        "1:\n" \
+        "add r2, pc, r2\n"  /* obtain GLOBAL_OFFSET_TABLE */    \
+        "ldr r3, 12f\n" \
+        "add r2, r2, r3\n" \
+        "bic r2, r2, #0xc0000000\n" /* SFI constraint */ \
+        "ldr r3, [r2]\n" /* obtain def_func */ \
+        "str r3, [sp, #0x3c]\n" \
+        "b 2f\n" /* leave some space for PC-relative data. */ \
+        "11:\n" \
+        ".long _GLOBAL_OFFSET_TABLE_-(1b + 8)\n" \
+        "12:\n" \
+        ".long " #def_func "(GOT)\n" \
+        "2:\n" \
         /* Save CPSR (flags) register, a.k.a. APSR for user mode */ \
         "mrs r0, apsr\n" \
         "str r0, [sp, #0x40]\n" \
         /* Set argument to callee_func() */ \
         "mov r0, sp\n" \
         /* Align the stack pointer */ \
         "bic sp, sp, #0xc000000f\n" \
         "b " #callee_func "\n" \
         ".popsection\n")
 
@@ skipping 91 matching lines @@
 void RegsUnsetNonCalleeSavedRegisters(struct NaClSignalContext *regs);
 
 /*
  * For a function called with register state |regs|, extract the first
  * argument.  This is useful for a function entry point defined by
  * REGS_SAVER_FUNC.
  */
 uintptr_t RegsGetArg1(const struct NaClSignalContext *regs);
 
 #endif