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Disable read-only GS cookie protection on Apple platforms (fixes coreclr_initialize under stock LLDB) #132925

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Disable read-only GS cookie protection on Apple platforms (fixes coreclr_initialize under stock LLDB) #132925

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4 changes: 4 additions & 0 deletions src/coreclr/vm/ceemain.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -470,6 +470,7 @@ void InitGSCookie()

volatile GSCookie * pGSCookiePtr = GetProcessGSCookiePtr();

#ifdef FEATURE_READONLY_GS_COOKIE
// The GS cookie is stored in a read only data segment
DWORD oldProtection;
if(!ClrVirtualProtect((LPVOID)pGSCookiePtr, sizeof(GSCookie), PAGE_READWRITE, &oldProtection))
Expand All @@ -481,6 +482,7 @@ void InitGSCookie()
// PAL layer is unable to extract old protection for regions that were not allocated using VirtualAlloc
oldProtection = PAGE_READONLY;
#endif // TARGET_UNIX
#endif // FEATURE_READONLY_GS_COOKIE

#ifndef TARGET_UNIX
// The GSCookie cannot be in a writeable page
Expand All @@ -507,10 +509,12 @@ void InitGSCookie()
val ++;
*pGSCookiePtr = val;

#ifdef FEATURE_READONLY_GS_COOKIE
if(!ClrVirtualProtect((LPVOID)pGSCookiePtr, sizeof(GSCookie), oldProtection, &oldProtection))
{
ThrowLastError();
}
#endif // FEATURE_READONLY_GS_COOKIE
}

Volatile<BOOL> g_bIsGarbageCollectorFullyInitialized = FALSE;
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4 changes: 4 additions & 0 deletions src/coreclr/vm/vars.cpp
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Expand Up @@ -252,7 +252,11 @@ void OBJECTREF_EnumMemoryRegions(OBJECTREF ref)
//
// We need the following to be the compiler's notion of volatile.
//
#ifdef FEATURE_READONLY_GS_COOKIE
extern "C" RAW_KEYWORD(volatile) const GSCookie s_gsCookie = 0;
#else
extern "C" RAW_KEYWORD(volatile) GSCookie s_gsCookie = 0;
#endif

#else
__GlobalVal< GSCookie > s_gsCookie(&DacGlobals::dac__s_gsCookie);
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10 changes: 10 additions & 0 deletions src/coreclr/vm/vars.hpp
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Expand Up @@ -593,12 +593,22 @@ typedef DPTR(GSCookie) PTR_GSCookie;
#define READONLY_ATTR __attribute__((READONLY_ATTR_ARGS))
#endif

// Apple's __DATA_CONST segment is immutable at runtime, so InitGSCookie's ClrVirtualProtect
// call fails there (see nativeaot/Runtime for the same FEATURE_READONLY_GS_COOKIE guard).
#ifndef TARGET_APPLE
#define FEATURE_READONLY_GS_COOKIE
#endif

#ifndef DACCESS_COMPILE
// const is so that it gets placed in the .text section (which is read-only)
// volatile is so that accesses to it do not get optimized away because of the const
//

Comment on lines 603 to 606
#ifdef FEATURE_READONLY_GS_COOKIE
extern "C" RAW_KEYWORD(volatile) READONLY_ATTR const GSCookie s_gsCookie;
#else
extern "C" RAW_KEYWORD(volatile) GSCookie s_gsCookie;
#endif

inline
GSCookie * GetProcessGSCookiePtr() { return const_cast<GSCookie *>(&s_gsCookie); }
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