commit ebc8fe19f8de8bf027aa271e1f76200333a811b8
author David Anderson <dvander@google.com> Fri Jun 17 19:17:43 2022 -0700
committer David Anderson <dvander@google.com> Tue Jun 21 19:32:19 2022 -0700
tree 70745f0d48f63e62d0f1db6df8101c1624976358
parent cef4850d9ff93abd130a3aa02c2a9938d05f6743

fastboot: Add a command to get current kernel logs.

This adds "fastboot getvar dmesg", usable only in userspace fastboot,
and only on unlocked devices. This is to debug flashing failures when
serial log access is not available.

Bug: 230269532
Test: fastboot getvar dmesg
Change-Id: Ic57881e362efe3f0687f41ab986d30b3a59dc4e4

fastboot/device/variables.cpp

diff --git a/fastboot/device/variables.cpp b/fastboot/device/variables.cpp
index 0cf4699..0de00b1 100644
--- a/fastboot/device/variables.cpp
+++ b/fastboot/device/variables.cpp
@@ -17,6 +17,7 @@
 #include "variables.h"
 
 #include <inttypes.h>
+#include <stdio.h>
 
 #include <android-base/file.h>
 #include <android-base/logging.h>
@@ -28,6 +29,7 @@
 #include <fs_mgr.h>
 #include <liblp/liblp.h>
 
+#include "constants.h"
 #include "fastboot_device.h"
 #include "flashing.h"
 #include "utility.h"
@@ -46,6 +48,7 @@
 using ::android::hardware::fastboot::V1_0::Status;
 using IBootControl1_1 = ::android::hardware::boot::V1_1::IBootControl;
 using namespace android::fs_mgr;
+using namespace std::string_literals;
 
 constexpr char kFastbootProtocolVersion[] = "0.4";
 
@@ -518,3 +521,36 @@
     *message = android::base::StringPrintf("0x%X", kMaxFetchSizeDefault);
     return true;
 }
+
+bool GetDmesg(FastbootDevice* device) {
+    if (GetDeviceLockStatus()) {
+        return device->WriteFail("Cannot use when device flashing is locked");
+    }
+
+    std::unique_ptr<FILE, decltype(&::fclose)> fp(popen("/system/bin/dmesg", "re"), ::fclose);
+    if (!fp) {
+        PLOG(ERROR) << "popen /system/bin/dmesg";
+        return device->WriteFail("Unable to run dmesg: "s + strerror(errno));
+    }
+
+    ssize_t rv;
+    size_t n = 0;
+    char* str = nullptr;
+    while ((rv = ::getline(&str, &n, fp.get())) > 0) {
+        if (str[rv - 1] == '\n') {
+            rv--;
+        }
+        device->WriteInfo(std::string(str, rv));
+    }
+
+    int saved_errno = errno;
+    ::free(str);
+
+    if (rv < 0 && saved_errno) {
+        LOG(ERROR) << "dmesg getline: " << strerror(saved_errno);
+        device->WriteFail("Unable to read dmesg: "s + strerror(saved_errno));
+        return false;
+    }
+
+    return true;
+}