simpleperf: fix symbolization for kernel modules.

Simpleperf makes a wrong assumption that the kernel always load
.text section of a kernel module at the start of its module memory.
This can map an ip addr of a module to a wrong symbol.
To fix it:
1. In KernelModuleDso, calculate min_vaddr and memory_offset, which
   are used to do the conversion in IpToVaddrInFile().
2. Change record_file_reader/writer to store min_vaddr and memory_offset
   of KernelModuleDso in the recording file.
3. To get module start addresses, Use CheckKernelSymbolAddress() in
   GetLoadedModules().

Bug: 174076407
Test: run simpleperf_unit_test.
Test: run simpleperf manually to check symbols of kernel modules.
Change-Id: I2498564f78dcc34761c5fe3ae9ffa6b88a98a048

1 files changed, 3 insertions, 0 deletions

diff --git a/simpleperf/environment.cpp b/simpleperf/environment.cpp
index f3333ca1..a154b4e7 100644
--- a/simpleperf/environment.cpp
+++ b/simpleperf/environment.cpp
@@ -95,6 +95,9 @@ std::vector<int> GetOnlineCpus() {
 }
 
 static std::vector<KernelMmap> GetLoadedModules() {
+  if (IsRoot() && !CheckKernelSymbolAddresses()) {
+    return {};
+  }
   std::vector<KernelMmap> result;
   FILE* fp = fopen("/proc/modules", "re");
   if (fp == nullptr) {