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Treat [vvar_vclock] the same way we treat [vvar].
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@khuey
khuey authored Jan 29, 2025
1 parent d66c4d1 commit d6c7343
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Showing 4 changed files with 67 additions and 30 deletions.
2 changes: 1 addition & 1 deletion src/AddressSpace.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -413,7 +413,7 @@ void AddressSpace::unmap_all_but_rr_mappings(AutoRemoteSyscalls& remote,
if (m.map.start() != AddressSpace::rr_page_start() &&
m.map.start() != AddressSpace::preload_thread_locals_start() &&
!m.map.is_vsyscall() &&
(!options.exclude_vdso_vvar || (!m.map.is_vdso() && m.map.is_vvar()))) {
(!options.exclude_vdso_vvar || (!m.map.is_vdso() && (m.map.is_vvar() || m.map.is_vvar_vclock())))) {
unmaps.push_back(m.map);
}
}
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1 change: 1 addition & 0 deletions src/AddressSpace.h
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Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,7 @@ class KernelMapping : public MemoryRange {
bool is_heap() const { return fsname() == "[heap]"; }
bool is_stack() const { return fsname().find("[stack") == 0; }
bool is_vvar() const { return fsname() == "[vvar]"; }
bool is_vvar_vclock() const { return fsname() == "[vvar_vclock]"; }
bool is_vsyscall() const { return fsname() == "[vsyscall]"; }
bool is_named_anonymous() const {
return fsname().find("[anon:") == 0 || fsname().find("[anon_shmem:") == 0;
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85 changes: 56 additions & 29 deletions src/Task.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -4054,6 +4054,12 @@ static void mremap_move(AutoRemoteSyscalls& remote, remote_ptr<void> src,
MREMAP_MAYMOVE | MREMAP_FIXED);
}

struct VMappings {
KernelMapping vdso;
KernelMapping vvar;
KernelMapping vvar_vclock;
};

/* Remap VDSO and VVAR to the addresses is used in the target process,
before they get unmapped.
Otherwise the kernel seems to put the address of the original
Expand All @@ -4062,55 +4068,75 @@ static void mremap_move(AutoRemoteSyscalls& remote, remote_ptr<void> src,
located in libpthread.so.0 is used.
*/
static void move_vdso_and_vvar_mappings(AutoRemoteSyscalls& remote,
const KernelMapping& vdso_new, const KernelMapping& vvar_new) {
KernelMapping vdso_current;
KernelMapping vvar_current;
const VMappings& new_) {
VMappings current;
Task* t = remote.task();
for (const auto& m : t->vm()->maps()) {
if (m.map.is_vdso()) {
vdso_current = m.map;
current.vdso = m.map;
} else if (m.map.is_vvar()) {
vvar_current = m.map;
current.vvar = m.map;
} else if (m.map.is_vvar_vclock()) {
current.vvar_vclock = m.map;
}
}

ASSERT(t, vdso_current.size() == vdso_new.size())
ASSERT(t, current.vdso.size() == new_.vdso.size())
<< "VDSO size mismatch";
ASSERT(t, vvar_current.size() == vvar_new.size() || !vvar_new.size())
ASSERT(t, current.vvar.size() == new_.vvar.size() || !new_.vvar.size())
<< "VVAR size mismatch";
ASSERT(t, current.vvar_vclock.size() == new_.vvar_vclock.size() || !new_.vvar_vclock.size())
<< "VVAR VCLOCK size mismatch";

// Handle case where old and new addresses overlap by finding a free range early in the
// address space we can use as a temporary buffer. VDSOs are always at fairly high
// addresses so this shouldn't introduce any new overlap issues.
// We move VDSO and VVAR to their temp addresses first, then move both of them to their
// final address, to avoid situations where current's VDSO overlaps target's VVAR or
// vice versa.
size_t temp_size = vdso_new.size() + vvar_new.size();
size_t temp_size = new_.vdso.size() + new_.vvar.size() + new_.vvar_vclock.size();
remote_ptr<void> vdso_temp_address = t->vm()->find_free_memory(t,
temp_size,
remote_ptr<void>(65536), AddressSpace::FindFreeMemoryPolicy::STRICT_SEARCH);
remote_ptr<void> vvar_temp_address = vdso_temp_address + vdso_new.size();
remote_ptr<void> vvar_temp_address = vdso_temp_address + new_.vdso.size();
remote_ptr<void> vvar_vclock_temp_address = vvar_temp_address + new_.vvar.size();
MemoryRange temp_range(vdso_temp_address, temp_size);
ASSERT(t, !temp_range.intersects(vdso_new))
ASSERT(t, !temp_range.intersects(new_.vdso))
<< "Free memory found overlaps new VDSO address";
ASSERT(t, !temp_range.intersects(vvar_new))
ASSERT(t, !temp_range.intersects(new_.vvar))
<< "Free memory found overlaps new VVAR address";

mremap_move(remote, vdso_current.start(), vdso_temp_address, vdso_new.size(),
"vdso_current.start() -> vdso_temp_address");
if (vvar_new.size()) {
mremap_move(remote, vvar_current.start(), vvar_temp_address, vvar_current.size(),
"vvar_current.start() -> vvar_temp_address");
ASSERT(t, !temp_range.intersects(new_.vvar_vclock))
<< "Free memory found overlaps new VVAR VCLOCK address";

mremap_move(remote, current.vdso.start(), vdso_temp_address, new_.vdso.size(),
"current.vdso.start() -> vdso_temp_address");
if (new_.vvar.size()) {
mremap_move(remote, current.vvar.start(), vvar_temp_address, current.vvar.size(),
"current.vvar.start() -> vvar_temp_address");
} else {
bool ok = remote.infallible_munmap_syscall_if_alive(vvar_current.start(),
vvar_current.size());
bool ok = remote.infallible_munmap_syscall_if_alive(current.vvar.start(),
current.vvar.size());
ASSERT(t, ok) << "Duped task got killed?";
t->vm()->unmap(t, vvar_current.start(), vvar_current.size());
t->vm()->unmap(t, current.vvar.start(), current.vvar.size());
}
if (new_.vvar_vclock.size()) {
mremap_move(remote, current.vvar_vclock.start(), vvar_vclock_temp_address,
current.vvar_vclock.size(),
"current.vvar_vclock.start() -> vvar_vclock_temp_address");
} else if (new_.vvar_vclock.start()) {
bool ok = remote.infallible_munmap_syscall_if_alive(current.vvar_vclock.start(),
current.vvar_vclock.size());
ASSERT(t, ok) << "Duped task got killed?";
t->vm()->unmap(t, current.vvar_vclock.start(), current.vvar_vclock.size());
}
mremap_move(remote, vdso_temp_address, new_.vdso.start(), new_.vdso.size(),
"vdso_temp_address -> new_.vdso.start()");
mremap_move(remote, vvar_temp_address, new_.vvar.start(), new_.vvar.size(),
"vvar_temp_address -> new_.vvar.start()");
if (new_.vvar_vclock.start()) {
mremap_move(remote, vvar_vclock_temp_address, new_.vvar_vclock.start(), new_.vvar_vclock.size(),
"vvar_vclock_temp_address -> new_.vvar_vclock.start()");
}
mremap_move(remote, vdso_temp_address, vdso_new.start(), vdso_new.size(),
"vdso_temp_address -> vdso_new.start()");
mremap_move(remote, vvar_temp_address, vvar_new.start(), vvar_new.size(),
"vvar_temp_address -> vvar_new.start()");
}

const int all_rlimits[] = {
Expand All @@ -4124,8 +4150,7 @@ void Task::dup_from(Task *other) {
std::vector<KernelMapping> mappings;
KernelMapping stack_mapping;
bool found_stack = false;
KernelMapping vdso_mapping;
KernelMapping vvar_mapping;
VMappings vmaps;

for (auto map : other->vm()->maps()) {
auto km = map.map;
Expand All @@ -4146,9 +4171,11 @@ void Task::dup_from(Task *other) {
found_stack = true;
} else {
if (km.is_vdso()) {
vdso_mapping = km;
vmaps.vdso = km;
} else if (km.is_vvar()) {
vvar_mapping = km;
vmaps.vvar = km;
} else if (km.is_vvar_vclock()) {
vmaps.vvar_vclock = km;
} else if (!km.is_vsyscall()) {
mappings.push_back(km);
}
Expand All @@ -4163,7 +4190,7 @@ void Task::dup_from(Task *other) {
}
{
AutoRemoteSyscalls remote(this, AutoRemoteSyscalls::DISABLE_MEMORY_PARAMS);
move_vdso_and_vvar_mappings(remote, vdso_mapping, vvar_mapping);
move_vdso_and_vvar_mappings(remote, vmaps);
LOG(debug) << "Unmapping memory for " << tid;
// TODO: Only do this if the rr page isn't already mapped
AddressSpace::UnmapOptions options;
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9 changes: 9 additions & 0 deletions src/record_syscall.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -5782,6 +5782,7 @@ static void process_execve(RecordTask* t, TaskSyscallState& syscall_state) {
ASSERT(t, mode == TraceWriter::DONT_RECORD_IN_TRACE);

KernelMapping vvar;
KernelMapping vvar_vclock;
KernelMapping vdso;

// get the remote executable entry point
Expand All @@ -5800,6 +5801,8 @@ static void process_execve(RecordTask* t, TaskSyscallState& syscall_state) {
stacks.push_back(km);
} else if (km.is_vvar()) {
vvar = km;
} else if (km.is_vvar_vclock()) {
vvar_vclock = km;
} else if (km.is_vdso()) {
vdso = km;
}
Expand Down Expand Up @@ -5834,6 +5837,12 @@ static void process_execve(RecordTask* t, TaskSyscallState& syscall_state) {
vvar.start(), vvar.size());
t->vm()->unmap(t, vvar.start(), vvar.size());
}
if (vvar_vclock.size()) {
// Give [vvar_vclock] the same treatment.
remote.infallible_syscall(syscall_number_for_munmap(remote.arch()),
vvar_vclock.start(), vvar_vclock.size());
t->vm()->unmap(t, vvar_vclock.start(), vvar_vclock.size());
}

if (t->session().unmap_vdso() && vdso.size()) {
remote.infallible_syscall(syscall_number_for_munmap(remote.arch()),
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