From 8ff7a1c957999d8e84d0b1ffd5b91e976754cc8b Mon Sep 17 00:00:00 2001
From: Lepton Wu <lepton@chromium.org>
Date: Mon, 22 Jun 2020 15:33:32 -0700
Subject: [PATCH] mapi: x86: Fix dynamic entries in x86 tsd stubs.

We need to update dynamic entries related code after updating
asm stubs.

Fixes: 45206d7673a ("mapi: Adapted libglvnd x86 tsd changes")
Signed-off-by: Lepton Wu <lepton@chromium.org>
---
 src/mapi/entry_x86_tsd.h | 50 +++++++++++++++++++++++++++++++++-------
 1 file changed, 42 insertions(+), 8 deletions(-)

diff --git a/src/mapi/entry_x86_tsd.h b/src/mapi/entry_x86_tsd.h
index 1cf3ea2964e..f5d9c41253f 100644
--- a/src/mapi/entry_x86_tsd.h
+++ b/src/mapi/entry_x86_tsd.h
@@ -39,8 +39,16 @@
 
 #define X86_ENTRY_SIZE 64
 
-__asm__(".text\n"
-        ".balign 32\n"
+__asm__(".text\n");
+
+__asm__("x86_got:\n\t"
+        "call 1f\n"
+        "1:\n\t"
+        "popl %eax\n\t"
+        "addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %eax\n\t"
+        "ret");
+
+__asm__(".balign 32\n"
         "x86_entry_start:");
 
 #define STUB_ASM_ENTRY(func)        \
@@ -49,11 +57,17 @@ __asm__(".text\n"
    ".balign 32\n"                   \
    func ":"
 
+#define LOC_BEGIN_SET_ECX
+#define LOC_END_SET_ECX
+#define LOC_END_JMP
+
 #define STUB_ASM_CODE(slot)         \
+   LOC_BEGIN_SET_ECX	            \
    "call 1f\n\t"                    \
    "1:\n\t"                         \
    "popl %ecx\n\t"                  \
    "addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx\n\t" \
+   LOC_END_SET_ECX                                \
    "movl " ENTRY_CURRENT_TABLE "@GOT(%ecx), %eax\n\t" \
    "mov (%eax), %eax\n\t"           \
    "testl %eax, %eax\n\t"           \
@@ -64,7 +78,8 @@ __asm__(".text\n"
    "call " ENTRY_CURRENT_TABLE_GET "@PLT\n\t" \
    "popl %ebx\n\t"                  \
    "1:\n\t"                         \
-   "jmp *(4 * " slot ")(%eax)"
+   "jmp *(4 * " slot ")(%eax)\n\t" \
+   LOC_END_JMP
 
 #define MAPI_TMP_STUB_ASM_GCC
 #include "mapi_tmp.h"
@@ -74,9 +89,26 @@ __asm__(".text\n"
 __asm__(".balign 32\n"
         "x86_entry_end:");
 
+#undef LOC_BEGIN_SET_ECX
+#undef LOC_END_SET_ECX
+#undef LOC_END_JMP
+#define LOC_BEGIN_SET_ECX "jmp set_ecx\n\t"
+#define LOC_END_SET_ECX "set_ecx:movl $0x12345678, %ecx\n\tloc_end_set_ecx:\n\t"
+#define LOC_END_JMP "loc_end_jmp:"
+
+/* Any number big enough works. This is to make sure the final
+ * jmp is a long jmp */
+__asm__(STUB_ASM_CODE("10000"));
+
+extern const char loc_end_set_ecx[] HIDDEN;
+extern const char loc_end_jmp[] HIDDEN;
+
 #include <string.h>
 #include "u_execmem.h"
 
+extern unsigned long
+x86_got();
+
 extern const char x86_entry_start[] HIDDEN;
 extern const char x86_entry_end[] HIDDEN;
 
@@ -95,16 +127,15 @@ void
 entry_patch(mapi_func entry, int slot)
 {
    char *code = (char *) entry;
-
-   *((unsigned long *) (code + 11)) = slot * sizeof(mapi_func);
-   *((unsigned long *) (code + 22)) = slot * sizeof(mapi_func);
+   int offset = loc_end_jmp - x86_entry_end - sizeof(unsigned long);
+   *((unsigned long *) (code + offset)) = slot * sizeof(mapi_func);
 }
 
 mapi_func
 entry_generate(int slot)
 {
-   const char *code_templ = x86_entry_end - X86_ENTRY_SIZE;
-   void *code;
+   const char *code_templ = x86_entry_end;
+   char *code;
    mapi_func entry;
 
    code = u_execmem_alloc(X86_ENTRY_SIZE);
@@ -113,6 +144,9 @@ entry_generate(int slot)
 
    memcpy(code, code_templ, X86_ENTRY_SIZE);
    entry = (mapi_func) code;
+   int ecx_value_off = loc_end_set_ecx - x86_entry_end - sizeof(unsigned long);
+   *((unsigned long *) (code + ecx_value_off)) = x86_got();
+
    entry_patch(entry, slot);
 
    return entry;
-- 
2.26.2