From: John Hodge <tpg@mutabah.net>
Date: Mon, 18 Aug 2014 10:30:49 +0000 (+0800)
Subject: Usermode/ld-acess - Fix dynamic linking quirk (STB_WEAK and R_COPY)
X-Git-Url: https://git.ucc.asn.au/?a=commitdiff_plain;h=89fa44978be88e59366ee3e8939a1621f1ebc146;p=tpg%2Facess2.git

Usermode/ld-acess - Fix dynamic linking quirk (STB_WEAK and R_COPY)
---

diff --git a/Usermode/Libraries/ld-acess.so_src/elf.c b/Usermode/Libraries/ld-acess.so_src/elf.c
index 0adb2a70..e3109b4a 100644
--- a/Usermode/Libraries/ld-acess.so_src/elf.c
+++ b/Usermode/Libraries/ld-acess.so_src/elf.c
@@ -4,8 +4,10 @@
  *
  * elf.c
  * - ELF32/ELF64 relocation
+ *
+ * TODO: Have GetSymbol() return a symbol "strength" on success. Allows STB_WEAK to be overriden by STB_GLOBAL
  */
-#ifndef DEBUG	// This code is #include'd from the kernel, so DEBUG may already be defined
+#ifndef KERNEL_VERSION
 # define DEBUG	0
 #endif
 
@@ -29,7 +31,8 @@
 
 #define WARNING(f,...)	SysDebug("WARN: "f ,## __VA_ARGS__)	// Malformed file
 #define NOTICE(f,...)	SysDebug("NOTICE: "f ,## __VA_ARGS__)	// Missing relocation
-#define TRACE(f,...)	DEBUG_OUT("TRACE:%s:%i "f, __func__, __LINE__ ,## __VA_ARGS__)	// Debugging trace
+//#define TRACE(f,...)	DEBUG_OUT("TRACE:%s:%i "f, __func__, __LINE__ ,## __VA_ARGS__)	// Debugging trace
+#define TRACE(f,...)	DEBUG_OUT("TRACE:%s "f, __func__,## __VA_ARGS__)	// Debugging trace
 
 #ifndef DISABLE_ELF64
 # define SUPPORT_ELF64
@@ -234,7 +237,6 @@ void *Elf32Relocate(void *Base, char **envp, const char *Filename)
 	const Elf32_Ehdr	*hdr = Base;
 	char	*libPath;
 	intptr_t	iRealBase = -1;
-	intptr_t	iBaseDiff;
 	Elf32_Rel	*rel = NULL;
 	Elf32_Rela	*rela = NULL;
 	void	*plt = NULL;
@@ -275,10 +277,11 @@ void *Elf32Relocate(void *Base, char **envp, const char *Filename)
 	
 	// Page Align real base
 	iRealBase &= ~0xFFF;
-	TRACE("True Base = 0x%x, Compiled Base = 0x%x", Base, iRealBase);
 	
 	// Adjust "Real" Base
-	iBaseDiff = (intptr_t)Base - iRealBase;
+	const intptr_t	iBaseDiff = (intptr_t)Base - iRealBase;
+
+	TRACE("True Base = 0x%x, Compiled Base = 0x%x, Difference = 0x%x", Base, iRealBase, iBaseDiff);
 
 	// Check if a PT_DYNAMIC segement was found
 	if(!dynamicTab) {
@@ -357,17 +360,18 @@ void *Elf32Relocate(void *Base, char **envp, const char *Filename)
 			size_t	newsize;
 			if( ELF32_ST_BIND(sym->st_info) != STB_WEAK )
 			{
-				TRACE("Sym %i'%s' %p += 0x%x", i, name, sym->st_value, iBaseDiff);
+				TRACE("Sym %i'%s' = %p (local)", i, name, sym->st_value + iBaseDiff);
 				sym->st_value += iBaseDiff;
 			}
-			else if( !GetSymbol(name, &newval, &newsize, Base) )
+			// If GetSymbol doesn't return a strong/global symbol value
+			else if( GetSymbol(name, &newval, &newsize, Base) != 1 )
 			{
-				TRACE("Sym %i'%s' %p += 0x%x (Local weak)", i, name, sym->st_value, iBaseDiff);
+				TRACE("Sym %i'%s' = %p (Local weak)", i, name, sym->st_value + iBaseDiff);
 				sym->st_value += iBaseDiff;
 			}
 			else
 			{
-				TRACE("Sym %i'%s' %p = %p+0x%x (Extern weak)", i, name, newval, newsize);
+				TRACE("Sym %i'%s' = %p+0x%x (Extern weak)", i, name, newval, newsize);
 				sym->st_value = (uintptr_t)newval;
 				sym->st_size = newsize;
 			}
@@ -690,14 +694,18 @@ int Elf32GetSymbolInfo(void *Base, const char *Name, void **Addr, size_t *Size,
 
 int Elf32GetSymbol(void *Base, const char *Name, void **ret, size_t *Size)
 {
-	 int	section;
+	 int	section, binding;
 	TRACE("Elf32GetSymbol(%p,%s,...)", Base, Name);
-	if( Elf32GetSymbolInfo(Base, Name, ret, Size, &section, NULL, NULL) )
+	if( Elf32GetSymbolInfo(Base, Name, ret, Size, &section, &binding, NULL) )
 		return 0;
 	if( section == SHN_UNDEF ) {
-		TRACE("Elf32GetSymbol: Undefined", *ret, (Size?*Size:0), section);
+		TRACE("Elf32GetSymbol: Undefined %p", *ret, (Size?*Size:0), section);
 		return 0;
 	}
+	if( binding == STB_WEAK ) {
+		TRACE("Elf32GetSymbol: Weak, return %p+0x%x,section=%i", *ret, (Size?*Size:0), section);
+		return 2;
+	}
 	TRACE("Elf32GetSymbol: Found %p+0x%x,section=%i", *ret, (Size?*Size:0), section);
 	return 1;
 }
diff --git a/Usermode/Libraries/ld-acess.so_src/loadlib.c b/Usermode/Libraries/ld-acess.so_src/loadlib.c
index dbb7c156..1c750a8f 100644
--- a/Usermode/Libraries/ld-acess.so_src/loadlib.c
+++ b/Usermode/Libraries/ld-acess.so_src/loadlib.c
@@ -4,6 +4,7 @@
 */
 #include "common.h"
 #include <stdint.h>
+#include <stdbool.h>
 #include <acess/sys.h>
 
 #define DEBUG	0
@@ -266,7 +267,8 @@ int GetSymbol(const char *name, void **Value, size_t *Size, void *IgnoreBase)
 			return 1;
 		}
 	}
-	
+
+	bool have_weak = false;	
 	for(int i = 0; i < MAX_LOADED_LIBRARIES && gLoadedLibraries[i].Base != 0; i ++)
 	{
 		// Allow ignoring the current module
@@ -277,13 +279,25 @@ int GetSymbol(const char *name, void **Value, size_t *Size, void *IgnoreBase)
 		
 		//SysDebug(" GetSymbol: Trying 0x%x, '%s'",
 		//	gLoadedLibraries[i].Base, gLoadedLibraries[i].Name);
-		if(GetSymbolFromBase(gLoadedLibraries[i].Base, name, Value, Size)) {
-			//SysDebug("GetSymbol: Remote %p - %p", gLoadedLibraries[i].Base, *Value);
-			return 1;
+		void	*tmpval;
+		size_t	tmpsize;
+		int rv = GetSymbolFromBase(gLoadedLibraries[i].Base, name, &tmpval, &tmpsize);
+		if(rv)
+		{
+			*Value = tmpval;
+			*Size = tmpsize;
+			if( rv == 1 ) {
+				return 1;
+			}
+			have_weak = true;
 		}
 	}
-	//SysDebug("GetSymbol: None");
-	return 0;
+	if(have_weak) {
+		return 2;
+	}
+	else {
+		return 0;
+	}
 }
 
 /**