From dc9c08b9001e2b892ccbc7dc2c86a53ab5964b63 Mon Sep 17 00:00:00 2001
From: Yifan Hong <elsk@google.com>
Date: Mon, 25 Mar 2019 18:09:35 -0700
Subject: [PATCH] charger: android_get_control_file on last_kmsg

Call android_get_control_file on last_kmsg files if the file
descriptor is provided by init.

Also, uses base::Read(File|Fd)ToString functions to read the
files (because load_file doesn't support fd arguments).

Test: charger mode
Test: manual kernel panic, then start charger; seen last kmsg.

Bug: 129138950
Change-Id: Idd3376e349f29586a1e66faab2c0f1bf73e0eda5
---
 healthd/healthd_mode_charger.cpp | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/healthd/healthd_mode_charger.cpp b/healthd/healthd_mode_charger.cpp
index 5fe58ac5a..bde5fbe4a 100644
--- a/healthd/healthd_mode_charger.cpp
+++ b/healthd/healthd_mode_charger.cpp
@@ -36,6 +36,7 @@
 #include <linux/netlink.h>
 #include <sys/socket.h>
 
+#include <cutils/android_get_control_file.h>
 #include <cutils/klog.h>
 #include <cutils/misc.h>
 #include <cutils/properties.h>
@@ -206,10 +207,9 @@ static int64_t curr_time_ms() {
 #define MAX_KLOG_WRITE_BUF_SZ 256
 
 static void dump_last_kmsg(void) {
-    char* buf;
+    std::string buf;
     char* ptr;
-    unsigned sz = 0;
-    int len;
+    size_t len;
 
     LOGW("\n");
     LOGW("*************** LAST KMSG ***************\n");
@@ -221,21 +221,25 @@ static void dump_last_kmsg(void) {
         "/proc/last_kmsg",
         // clang-format on
     };
-    for (size_t i = 0; i < arraysize(kmsg); ++i) {
-        buf = (char*)load_file(kmsg[i], &sz);
-        if (buf && sz) break;
+    for (size_t i = 0; i < arraysize(kmsg) && buf.empty(); ++i) {
+        auto fd = android_get_control_file(kmsg[i]);
+        if (fd >= 0) {
+            android::base::ReadFdToString(fd, &buf);
+        } else {
+            android::base::ReadFileToString(kmsg[i], &buf);
+        }
     }
 
-    if (!buf || !sz) {
+    if (buf.empty()) {
         LOGW("last_kmsg not found. Cold reset?\n");
         goto out;
     }
 
-    len = min(sz, LAST_KMSG_MAX_SZ);
-    ptr = buf + (sz - len);
+    len = min(buf.size(), LAST_KMSG_MAX_SZ);
+    ptr = &buf[buf.size() - len];
 
     while (len > 0) {
-        int cnt = min(len, MAX_KLOG_WRITE_BUF_SZ);
+        size_t cnt = min(len, MAX_KLOG_WRITE_BUF_SZ);
         char yoink;
         char* nl;
 
@@ -251,8 +255,6 @@ static void dump_last_kmsg(void) {
         ptr += cnt;
     }
 
-    free(buf);
-
 out:
     LOGW("\n");
     LOGW("************* END LAST KMSG *************\n");