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Diffstat (limited to 'src/vm/amd64/jithelpers_slow.S')
| -rw-r--r-- | src/vm/amd64/jithelpers_slow.S | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/src/vm/amd64/jithelpers_slow.S b/src/vm/amd64/jithelpers_slow.S new file mode 100644 index 0000000000..0a5da69393 --- /dev/null +++ b/src/vm/amd64/jithelpers_slow.S @@ -0,0 +1,113 @@ +// Licensed to the .NET Foundation under one or more agreements. +// The .NET Foundation licenses this file to you under the MIT license. +// See the LICENSE file in the project root for more information. + +.intel_syntax noprefix +#include "unixasmmacros.inc" + +#ifdef _DEBUG +// Version for when we're sure to be in the GC, checks whether or not the card +// needs to be updated +// +// void JIT_WriteBarrier_Debug(Object** dst, Object* src) +LEAF_ENTRY JIT_WriteBarrier_Debug, _TEXT + +#ifdef WRITE_BARRIER_CHECK + // **ALSO update the shadow GC heap if that is enabled** + // Do not perform the work if g_GCShadow is 0 + PREPARE_EXTERNAL_VAR g_GCShadow, rax + cmp qword ptr [rax], 0 + je NoShadow + + // If we end up outside of the heap don't corrupt random memory + mov r10, rdi + PREPARE_EXTERNAL_VAR g_lowest_address, r11 + sub r10, [r11] + jb NoShadow + + // Check that our adjusted destination is somewhere in the shadow gc + add r10, [rax] + PREPARE_EXTERNAL_VAR g_GCShadowEnd, r11 + cmp r10, [r11] + ja NoShadow + + // Write ref into real GC// see comment below about possibility of AV + mov [rdi], rsi + // Write ref into shadow GC + mov [r10], rsi + + // Ensure that the write to the shadow heap occurs before the read from + // the GC heap so that race conditions are caught by INVALIDGCVALUE + mfence + + // Check that GC/ShadowGC values match + mov r11, [rdi] + mov rax, [r10] + cmp rax, r11 + je DoneShadow + movabs r11, INVALIDGCVALUE + mov [r10], r11 + + jmp DoneShadow + + // If we don't have a shadow GC we won't have done the write yet + NoShadow: +#endif + + mov rax, rsi + + // Do the move. It is correct to possibly 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 [rdi], rax + +#ifdef WRITE_BARRIER_CHECK + // If we had a shadow GC then we already wrote to the real GC at the same time + // as the shadow GC so we want to jump over the real write immediately above + DoneShadow: +#endif + +#ifdef FEATURE_USE_SOFTWARE_WRITE_WATCH_FOR_GC_HEAP + // Update the write watch table if necessary + PREPARE_EXTERNAL_VAR g_sw_ww_enabled_for_gc_heap, r10 + cmp byte ptr [r10], 0h + je CheckCardTable_Debug + mov r10, rdi + shr r10, 0Ch // SoftwareWriteWatch::AddressToTableByteIndexShift + PREPARE_EXTERNAL_VAR g_sw_ww_table, r11 + add r10, qword ptr [r11] + cmp byte ptr [r10], 0h + jne CheckCardTable_Debug + mov byte ptr [r10], 0FFh +#endif + + CheckCardTable_Debug: + // See if we can just quick out + PREPARE_EXTERNAL_VAR g_ephemeral_low, r10 + cmp rax, [r10] + jb Exit_Debug + PREPARE_EXTERNAL_VAR g_ephemeral_high, r10 + cmp rax, [r10] + jnb Exit_Debug + + // Check if we need to update the card table + // Calc pCardByte + shr rdi, 0x0B + PREPARE_EXTERNAL_VAR g_card_table, r10 + add rdi, [r10] + + // Check if this card is dirty + cmp byte ptr [rdi], 0FFh + jne UpdateCardTable_Debug + REPRET + + UpdateCardTable_Debug: + mov byte ptr [rdi], 0FFh + ret + + .balign 16 + Exit_Debug: + REPRET +LEAF_END_MARKED JIT_WriteBarrier_Debug, _TEXT +#endif |