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[LLDB][NFC] Calculate the region size of an in memory image if size isn't specified #123148

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[LLDB][NFC] Calculate the region size of an in memory image if size isn't specified #123148

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23 changes: 22 additions & 1 deletion lldb/include/lldb/Target/Process.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1923,9 +1923,30 @@ class Process : public std::enable_shared_from_this<Process>,
/// the instruction has completed executing.
bool GetWatchpointReportedAfter();

/// Load a module image from memory.
///
/// \param[in] file_spec
/// The path to use to represent this module. This will show up in the
/// the image list.
///
/// \param[in] header_addr
/// The address of the object file header.
///
/// \param[in] size_to_read
/// The number of contiguous bytes to read that can be used to provide
/// all of the data for this module in memory. If this value is set to
/// zero, the memory region that contains \a header_addr will be found
/// and the size will be to the end address of this memory region. If
/// there is no memory region info that contains \a header_addr, then
/// default to 512 bytes.
///
/// \return
/// A valid module shared pointer if this succeeds, or an empty shared
/// pointer if no ObjectFile plug-ins recognize the object file header or
/// memory can not be read from \a header_addr.
lldb::ModuleSP ReadModuleFromMemory(const FileSpec &file_spec,
lldb::addr_t header_addr,
size_t size_to_read = 512);
size_t size_to_read = 0);

/// Attempt to get the attributes for a region of memory in the process.
///
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11 changes: 1 addition & 10 deletions lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
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Expand Up @@ -538,16 +538,7 @@ void DynamicLoaderPOSIXDYLD::LoadVDSO() {

FileSpec file("[vdso]");

MemoryRegionInfo info;
Status status = m_process->GetMemoryRegionInfo(m_vdso_base, info);
if (status.Fail()) {
Log *log = GetLog(LLDBLog::DynamicLoader);
LLDB_LOG(log, "Failed to get vdso region info: {0}", status);
return;
}

if (ModuleSP module_sp = m_process->ReadModuleFromMemory(
file, m_vdso_base, info.GetRange().GetByteSize())) {
if (ModuleSP module_sp = m_process->ReadModuleFromMemory(file, m_vdso_base)) {
UpdateLoadedSections(module_sp, LLDB_INVALID_ADDRESS, m_vdso_base, false);
m_process->GetTarget().GetImages().AppendIfNeeded(module_sp);
}
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20 changes: 20 additions & 0 deletions lldb/source/Target/Process.cpp
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Expand Up @@ -2544,6 +2544,26 @@ ModuleSP Process::ReadModuleFromMemory(const FileSpec &file_spec,
progress_up = std::make_unique<Progress>(
"Reading binary from memory", file_spec.GetFilename().GetString());

if (size_to_read == 0) {
// No size was provided, figure out the size of the memory region that
// contains "header_addr"
MemoryRegionInfo header_region_info;
Status error(GetMemoryRegionInfo(header_addr, header_region_info));
// Default to 512 in case we can't find a memory region.
size_to_read = 512;
if (error.Success()) {
// We found a memory region, set the range of bytes ro read to read to
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@Jlalond Jlalond Jan 16, 2025

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set the range of bytes ro read to read to the end of the memory region.

Typo plus maybe rephrase to

set the range to read to the end of the memory region.

// the end of the memory region. This should be enough to contain the
// file header and important bits.
const auto &range = header_region_info.GetRange();
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@Jlalond Jlalond Jan 16, 2025

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Echoing what Pavel said a little bit, I do think an upper bound makes sense. I think we can be pretty heavy handed with that upper-bound. I'm not an expert on ELF files by any means, but I suspect something like 10MB or even 100 MB, will be a sane expectation for even the largest set of ELF headers.

const addr_t end = range.GetRangeBase() + range.GetByteSize();
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@Jlalond Jlalond Jan 16, 2025

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Should this be an error?

The end should always be greater than the addr correct?

if (end > header_addr) {
const addr_t new_size = end - header_addr;
if (new_size > size_to_read)
size_to_read = new_size;
}
}
}
ObjectFile *objfile = module_sp->GetMemoryObjectFile(
shared_from_this(), header_addr, error, size_to_read);
if (objfile)
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