From aa874907283529c46ff8dcd6e5c1ac1c6642d3f0 Mon Sep 17 00:00:00 2001
From: KJ Tsanaktsidis <kj@kjtsanaktsidis.id.au>
Date: Fri, 12 Jul 2024 13:24:40 +1000
Subject: [PATCH] Set a mapping flag for per-thread scratch memory

Fixes https://github.com/rr-debugger/rr/issues/3779 (somehow)
---
 src/AddressSpace.h    | 2 ++
 src/record_syscall.cc | 1 +
 2 files changed, 3 insertions(+)

diff --git a/src/AddressSpace.h b/src/AddressSpace.h
index 2eae98a3b2a..1500cdf3210 100644
--- a/src/AddressSpace.h
+++ b/src/AddressSpace.h
@@ -315,6 +315,8 @@ class AddressSpace : public HasTaskSet {
       IS_RR_PAGE = 0x8,
       // This mapping is the rr vdso page
       IS_RR_VDSO_PAGE = 0x10,
+      // This mapping is the per-thread scratch space
+      IS_SCRATCH = 0x20,
     };
     uint32_t flags;
   };
diff --git a/src/record_syscall.cc b/src/record_syscall.cc
index 4817818e9dc..a74b24fdc0c 100644
--- a/src/record_syscall.cc
+++ b/src/record_syscall.cc
@@ -3375,6 +3375,7 @@ static void init_scratch_memory(RecordTask* t,
 
   KernelMapping km =
       t->vm()->map(t, t->scratch_ptr, sz, prot, flags, 0, string());
+  t->vm()->mapping_flags_of(t->scratch_ptr) |= AddressSpace::Mapping::IS_SCRATCH;
   struct stat stat;
   memset(&stat, 0, sizeof(stat));
   auto record_in_trace = t->trace_writer().write_mapped_region(t,