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[lldb] [Process/NetBSD] Fix handling piod_len from PT_IO calls 

Fix bugs in piod_len return value processing in ReadMemory()
and WriteMemory() methods.  In particular, add support for piod_len == 0
indicating EOF, and fix summing bytes_read/bytes_written when PT_IO does
partial reads/writes.

The EOF condition could happen if LLDB attempts to read past
vm.maxaddress, e.g. as a result of RBP containing large (invalid) value.
Previously, the 0 return caused the function to retry reading via PT_IO
indefinitely, effectively deadlooping lldb-server.

Partial reads probably did not occur in practice, yet they would cause
ReadMemory() to return incorrect bytes_read and/or overwrite previously
read data.

WriteMemory() suffered from analoguous problems.

Differential Revision: https://reviews.llvm.org/D61310

llvm-svn: 359572
This commit is contained in:
Michal Gorny 2019-04-30 16:30:32 +00:00
parent 68924e6be7
commit d14a0de9ad
1 changed files with 4 additions and 4 deletions
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8
lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
View File

@ -695,10 +695,10 @@ Status NativeProcessNetBSD::ReadMemory(lldb::addr_t addr, void *buf,
io.piod_addr = dst + bytes_read;
Status error = NativeProcessNetBSD::PtraceWrapper(PT_IO, GetID(), &io);
if (error.Fail())
if (error.Fail() || io.piod_len == 0)
return error;
bytes_read = io.piod_len;
bytes_read += io.piod_len;
io.piod_len = size - bytes_read;
} while (bytes_read < size);
@ -723,10 +723,10 @@ Status NativeProcessNetBSD::WriteMemory(lldb::addr_t addr, const void *buf,
io.piod_offs = (void *)(addr + bytes_written);
Status error = NativeProcessNetBSD::PtraceWrapper(PT_IO, GetID(), &io);
if (error.Fail())
if (error.Fail() || io.piod_len == 0)
return error;
bytes_written = io.piod_len;
bytes_written += io.piod_len;
io.piod_len = size - bytes_written;
} while (bytes_written < size);