Split off patched code into separate .S file and disable subsections-via-symbols for it

src/coreclr/vm/CMakeLists.txt

@@ -652,6 +652,7 @@ if(CLR_CMAKE_TARGET_ARCH_AMD64)
         ${ARCH_SOURCES_DIR}/JitHelpers_InlineGetThread.asm
         ${ARCH_SOURCES_DIR}/JitHelpers_SingleAppDomain.asm
         ${ARCH_SOURCES_DIR}/JitHelpers_Slow.asm
+        ${ARCH_SOURCES_DIR}/patchedcode.asm
         ${ARCH_SOURCES_DIR}/PInvokeStubs.asm
         ${ARCH_SOURCES_DIR}/RedirectedHandledJITCase.asm
         ${ARCH_SOURCES_DIR}/ThePreStubAMD64.asm
@@ -683,6 +684,7 @@ elseif(CLR_CMAKE_TARGET_ARCH_ARM64)
         ${ARCH_SOURCES_DIR}/AsmHelpers.asm
         ${ARCH_SOURCES_DIR}/CallDescrWorkerARM64.asm
         ${ARCH_SOURCES_DIR}/CrtHelpers.asm
+        ${ARCH_SOURCES_DIR}/patchedcode.asm
         ${ARCH_SOURCES_DIR}/PInvokeStubs.asm
         ${ARCH_SOURCES_DIR}/thunktemplates.asm
     )
@@ -705,6 +707,7 @@ else(CLR_CMAKE_TARGET_WIN32)
             ${ARCH_SOURCES_DIR}/jithelpers_fastwritebarriers.S
             ${ARCH_SOURCES_DIR}/jithelpers_singleappdomain.S
             ${ARCH_SOURCES_DIR}/jithelpers_slow.S
+            ${ARCH_SOURCES_DIR}/patchedcode.S
             ${ARCH_SOURCES_DIR}/pinvokestubs.S
             ${ARCH_SOURCES_DIR}/redirectedhandledjitcase.S
             ${ARCH_SOURCES_DIR}/theprestubamd64.S
@@ -738,6 +741,7 @@ else(CLR_CMAKE_TARGET_WIN32)
             ${ARCH_SOURCES_DIR}/asmhelpers.S
             ${ARCH_SOURCES_DIR}/calldescrworkerarm64.S
             ${ARCH_SOURCES_DIR}/crthelpers.S
+            ${ARCH_SOURCES_DIR}/patchedcode.S
             ${ARCH_SOURCES_DIR}/pinvokestubs.S
             ${ARCH_SOURCES_DIR}/thunktemplates.S
         )

src/coreclr/vm/amd64/JitHelpers_Fast.asm

@@ -50,188 +50,6 @@ endif
 extern JIT_InternalThrow:proc
 
 
-; Mark start of the code region that we patch at runtime
-LEAF_ENTRY JIT_PatchedCodeStart, _TEXT
-        ret
-LEAF_END JIT_PatchedCodeStart, _TEXT
-
-
-; This is used by the mechanism to hold either the JIT_WriteBarrier_PreGrow
-; or JIT_WriteBarrier_PostGrow code (depending on the state of the GC). It _WILL_
-; change at runtime as the GC changes. Initially it should simply be a copy of the
-; larger of the two functions (JIT_WriteBarrier_PostGrow) to ensure we have created
-; enough space to copy that code in.
-LEAF_ENTRY JIT_WriteBarrier, _TEXT
-        align 16
-
-ifdef _DEBUG
-        ; In debug builds, this just contains jump to the debug version of the write barrier by default
-        mov     rax, JIT_WriteBarrier_Debug
-        jmp     rax
-endif
-
-ifdef FEATURE_USE_SOFTWARE_WRITE_WATCH_FOR_GC_HEAP
-        ; JIT_WriteBarrier_WriteWatch_PostGrow64
-
-        ; Regarding patchable constants:
-        ; - 64-bit constants have to be loaded into a register
-        ; - The constants have to be aligned to 8 bytes so that they can be patched easily
-        ; - The constant loads have been located to minimize NOP padding required to align the constants
-        ; - Using different registers for successive constant loads helps pipeline better. Should we decide to use a special
-        ;   non-volatile calling convention, this should be changed to use just one register.
-
-        ; Do the move into the GC .  It is correct to take an AV here, the EH code
-        ; figures out that this came from a WriteBarrier and correctly maps it back
-        ; to the managed method which called the WriteBarrier (see setup in
-        ; InitializeExceptionHandling, vm\exceptionhandling.cpp).
-        mov     [rcx], rdx
-
-        ; Update the write watch table if necessary
-        mov     rax, rcx
-        mov     r8, 0F0F0F0F0F0F0F0F0h
-        shr     rax, 0Ch ; SoftwareWriteWatch::AddressToTableByteIndexShift
-        NOP_2_BYTE ; padding for alignment of constant
-        mov     r9, 0F0F0F0F0F0F0F0F0h
-        add     rax, r8
-        cmp     byte ptr [rax], 0h
-        jne     CheckCardTable
-        mov     byte ptr [rax], 0FFh
-
-        NOP_3_BYTE ; padding for alignment of constant
-
-        ; Check the lower and upper ephemeral region bounds
-    CheckCardTable:
-        cmp     rdx, r9
-        jb      Exit
-
-        NOP_3_BYTE ; padding for alignment of constant
-
-        mov     r8, 0F0F0F0F0F0F0F0F0h
-
-        cmp     rdx, r8
-        jae     Exit
-
-        nop ; padding for alignment of constant
-
-        mov     rax, 0F0F0F0F0F0F0F0F0h
-
-        ; Touch the card table entry, if not already dirty.
-        shr     rcx, 0Bh
-        cmp     byte ptr [rcx + rax], 0FFh
-        jne     UpdateCardTable
-        REPRET
-
-    UpdateCardTable:
-        mov     byte ptr [rcx + rax], 0FFh
-ifdef FEATURE_MANUALLY_MANAGED_CARD_BUNDLES
-        mov     rax, 0F0F0F0F0F0F0F0F0h
-        shr     rcx, 0Ah
-        cmp     byte ptr [rcx + rax], 0FFh
-        jne     UpdateCardBundleTable
-        REPRET
-
-    UpdateCardBundleTable:
-        mov     byte ptr [rcx + rax], 0FFh
-endif
-        ret
-
-    align 16
-    Exit:
-        REPRET
-
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-        NOP_3_BYTE
-
-else
-        ; JIT_WriteBarrier_PostGrow64
-
-        ; Do the move into the GC .  It is correct to take an AV here, the EH code
-        ; figures out that this came from a WriteBarrier and correctly maps it back
-        ; to the managed method which called the WriteBarrier (see setup in
-        ; InitializeExceptionHandling, vm\exceptionhandling.cpp).
-        mov     [rcx], rdx
-
-        NOP_3_BYTE ; padding for alignment of constant
-
-        ; Can't compare a 64 bit immediate, so we have to move them into a
-        ; register.  Values of these immediates will be patched at runtime.
-        ; By using two registers we can pipeline better.  Should we decide to use
-        ; a special non-volatile calling convention, this should be changed to
-        ; just one.
-
-        mov     rax, 0F0F0F0F0F0F0F0F0h
-
-        ; Check the lower and upper ephemeral region bounds
-        cmp     rdx, rax
-        jb      Exit
-
-        nop ; padding for alignment of constant
-
-        mov     r8, 0F0F0F0F0F0F0F0F0h
-
-        cmp     rdx, r8
-        jae     Exit
-
-        nop ; padding for alignment of constant
-
-        mov     rax, 0F0F0F0F0F0F0F0F0h
-
-        ; Touch the card table entry, if not already dirty.
-        shr     rcx, 0Bh
-        cmp     byte ptr [rcx + rax], 0FFh
-        jne     UpdateCardTable
-        REPRET
-
-    UpdateCardTable:
-        mov     byte ptr [rcx + rax], 0FFh
-ifdef FEATURE_MANUALLY_MANAGED_CARD_BUNDLES
-        mov     rax, 0F0F0F0F0F0F0F0F0h
-        shr     rcx, 0Ah
-        cmp     byte ptr [rcx + rax], 0FFh
-        jne     UpdateCardBundleTable
-        REPRET
-
-    UpdateCardBundleTable:
-        mov     byte ptr [rcx + rax], 0FFh
-endif
-        ret
-
-    align 16
-    Exit:
-        REPRET
-endif
-
-    ; make sure this is bigger than any of the others
-    align 16
-        nop
-LEAF_END_MARKED JIT_WriteBarrier, _TEXT
-
-; Mark start of the code region that we patch at runtime
-LEAF_ENTRY JIT_PatchedCodeLast, _TEXT
-        ret
-LEAF_END JIT_PatchedCodeLast, _TEXT
-
 ; JIT_ByRefWriteBarrier has weird semantics, see usage in StubLinkerX86.cpp
 ;
 ; Entry: