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/* jstack systemtap tapset, for extracting hotspot java backtraces.
Copyright (C) 2009, 2012 Red Hat Inc.
This file is part of IcedTea.
IcedTea is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
IcedTea is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with IcedTea; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
*/
/*
Provides helper functions to log and print hotspot java based backtraces.
jstack() provides up to 32 pure java frames from the current probe point
(space separated). jstack_print() does the same, but logs each frame
immediately. jstack_full() provides up to 32 "mixed" frames, including
full method signatures plus native code frames. print_jstack_full() does
the same, but prints eachs frame to the log immediately. To request
more or less frames use the jstack_n(), jstack_full_n(), print_jstack_n()
and print_jstack_full_n() variants. And to have full controll over the
amount of information included in each frame use the jstack_call()
function.
Currently only works with full path in process probes below.
When things don't seem to work look if the correct
jre/lib/[arch]/[client|server]/libjvm.so is used
and exists under /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64//.
This version of jstack.stp has been configured to instrument the
libjvm.so for arch amd64 installed at:
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so
Note that you need a systemtap version > 1.0.
Otherwise you will not be able to fetch global vars, which would show as:
semantic error: failed to retrieve location attribute for local
*/
/* Resolve multiple installed java versions conflict. */
@define _private %( %( systemtap_v >= "3.0" %? private %) %)
@define _check_match %(
%( systemtap_v >= "3.2" %? if (strpos(pp(), "/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/") < 0) next %)
%( systemtap_v < "3.2" && systemtap_v >= "3.0" %? if (pp() !~ "/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/") next %)
%)
@_private global CodeCache_heap;
@_private global sp_register;
/* On PowerPC there is a link register, but no frame pointer register. */
%(arch == "powerpc" %?
@_private global link_register;
%:
@_private global fp_register;
%)
@_private global pc_register;
@_private global ptr_size;
@_private global ptr_mask;
@_private global constantPool_size;
@_private global HeapBlock_Header_size;
@_private global vm_inited;
/* We need to collect some global symbol addresses that cannot be resolved
in a bare function and vm_init_end seems a good place to use. */
probe hotspot.vm_init_end8
{
/**
* The CodeCache class contains the static CodeHeap _heap that
* is malloced at the start of the vm run and holds all generated
* code. If the program counter is between the low and high memory
* marks of the CodeHeap then it is generated code. Note that the
* interpreter CodeBlob itself is also generated at runtime.
*
* The code heap is made up of segments which are described in the
* CodeHeap _segmap. Each segment is of size _segment_size, which
* must be an exact power of 2 (_log2_segment_size). For each segment
* the _segmap has an unsigned char which is 0xFF if the segment
* isn't used, 0 if the segment is the start of a block and N
* (Where in is 1 till 0xFE) to indicate the segment belongs to
* the segment at index - N (which can be recursive if a block
* contains more than 0xFE segments).
*/
CodeCache_heap[pid()] = %( systemtap_v >= "1.8"
%? @var("_heap@codeCache.cpp")
%: $_heap %);
// Should really check arch of user space (for 32bit jvm on 64bit kernel).
%( arch == "i386" %?
sp_register = "esp";
fp_register = "ebp";
pc_register = "eip";
ptr_size = 4;
ptr_mask = 0xFFFFFFFF;
%: %(arch == "x86_64" %?
sp_register = "rsp";
fp_register = "rbp";
pc_register = "rip";
ptr_size = 8; // XXX - might be probing 32-on-64 jvm.
ptr_mask = 0xFFFFFFFFFFFFFFFF;
%: %(arch == "arm64" %?
sp_register = "sp";
fp_register = "fp";
pc_register = "pc";
ptr_size = 8; // XXX - might be probing 32-on-64 jvm.
ptr_mask = 0xFFFFFFFFFFFFFFFF;
%: %(arch == "powerpc" %?
sp_register = "r1";
link_register = "link";
pc_register = "nip";
ptr_size = 8; // XXX - might be probing 32-on-64 jvm.
ptr_mask = 0xFFFFFFFFFFFFFFFF;
%:
sp_register = "";
fp_register = "";
pc_register = "";
ptr_size = 8;
ptr_mask = 0xFFFFFFFFFFFFFFFF;
error("unknown architecture")
%) %) %) %)
// Pretend we have an array at address zero and take address of second
// element and we have the size.
constantPool_size = &@cast(0, "ConstantPool")[1];
// Really should get from dwarf: @size("HeapBlock::Header"), @size("oopDesc")
HeapBlock_Header_size = 2 * ptr_size;
vm_inited[pid()] = 1;
}
probe hotspot.vm_shutdown
{
delete(CodeCache_heap[pid()]);
delete(vm_inited[pid()]);
}
function jstack:string()
{
@_check_match
// java backtraces can be a lot bigger, but we risk going over MAXACTION.
// 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
max_depth = 32;
return jstack_n(max_depth);
}
function jstack_n:string(max_depth:long)
{
@_check_match
// Whether to log the method signatures.
log_sig = 0;
// Set to zero to only print pure java frames
log_native = 0;
// whether to print or just return the frames as space separated string
print_frames = 0;
return jstack_call(max_depth, log_sig, log_native, print_frames);
}
function print_jstack()
{
@_check_match
// java backtraces can be a lot bigger, but we risk going over MAXACTION.
// 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
max_depth = 32;
return print_jstack_n(max_depth);
}
function print_jstack_n:string(max_depth:long)
{
@_check_match
// Whether to log the method signatures.
log_sig = 0;
// Set to zero to only print pure java frames
log_native = 0;
// whether to print or just return the frames as space separated string
print_frames = 1;
jstack_call(max_depth, log_sig, log_native, print_frames);
}
function jstack_full:string()
{
@_check_match
// java backtraces can be a lot bigger, but we risk going over MAXACTION.
// 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
max_depth = 32;
return jstack_full_n(max_depth);
}
function jstack_full_n:string(max_depth:long)
{
@_check_match
// Whether to log the method signatures.
log_sig = 1;
// Set to zero to only print pure java frames
log_native = 1;
// whether to print or just return the frames as space separated string
print_frames = 0;
return jstack_call(max_depth, log_sig, log_native, print_frames);
}
function print_jstack_full()
{
@_check_match
// java backtraces can be a lot bigger, but we risk going over MAXACTION.
// 32 frames only gives us ~32 actions per frame (with MAXACTION == 1024).
max_depth = 32;
return print_jstack_full_n(max_depth);
}
function print_jstack_full_n:string(max_depth:long)
{
@_check_match
// Whether to log the method signatures.
log_sig = 1;
// Set to zero to only print pure java frames
log_native = 1;
// whether to print or just return the frames as space separated string
print_frames = 1;
jstack_call(max_depth, log_sig, log_native, print_frames);
}
function jstack_call:string(max_depth:long, log_sig:long, log_native:long,
print_frames:long)
{
@_check_match
if (! vm_inited[pid()])
{
frame = "<vm-not-inited>";
if (print_frames)
{
log(frame);
return "";
}
else
return frame;
}
// Extract code bounds.
CodeCache_low = @cast(CodeCache_heap[pid()], "CodeHeap",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_memory->_low;
CodeCache_high = @cast(CodeCache_heap[pid()], "CodeHeap",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_memory->_high;
CodeHeap_log2_segment_size = @cast(CodeCache_heap[pid()],
"CodeHeap",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_log2_segment_size;
CodeCache_segmap_low = @cast(CodeCache_heap[pid()],
"CodeHeap",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_segmap->_low;
// Might want to sanity check above values.
// Loop through all the frames. The program counter is the starting
// point to find the CodeBlob corresponding to the current frame. In
// most cases the frame pointer will help us detect the class/method
// and next pc value. But we need the stack pointer to help us out
// to "recover" the previous fp in case we hit a code blob that didn't
// preserve it.
frames = "";
%(arch == "powerpc" %?
sp = register(sp_register);
fp = sp + 72; /* fp + (-3 * ptr_size) = 48, parameter save area offset */
link = register(link_register);
pc = register(pc_register);
%:
sp = register(sp_register);
fp = register(fp_register);
pc = register(pc_register);
%)
depth = 0;
while (pc != 0 && depth < max_depth)
{
frame = "";
// Assume things are fine unless indicated otherwise.
trust_fp = 1;
// Generated code? (Interpreter and stub methods are also generated)
if (CodeCache_low <= pc && pc < CodeCache_high)
{
// Find the start of the code segment and code block that
// this pc is in.
segments = 0;
segment = (pc - CodeCache_low) >> CodeHeap_log2_segment_size;
tag = user_char(CodeCache_segmap_low + segment) & 0xFF;
while (tag > 0 && segments < 16)
{
segment = segment - tag;
tag = user_char(CodeCache_segmap_low + segment) & 0xFF;
segments++;
}
block = CodeCache_low + (segment << CodeHeap_log2_segment_size);
// Some of this is "fuzzy" so catch any read error in case we
// "guessed" wrong.
try
{
// Do some sanity checking.
used = @cast(block, "HeapBlock",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_header->_used;
if (used != 1)
{
// Something very odd has happened.
frame = sprintf("<unused_code_block@0x%x>", pc);
blob_name = "unused";
trust_fp = 0;
frame_size = 0;
}
else
{
// We don't like spaces in frames (makes it hard to return
// a space separated frame list). So make sure they are
// replaced by underscores when used in frames.
blob = block + HeapBlock_Header_size;
blob_name_ptr = @cast(blob, "CodeBlob",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_name;
blob_name = ((blob_name_ptr == 0) ? "<unknown-code-blob>"
: user_string(blob_name_ptr));
}
// For compiled code the methodOop is part of the code blob.
// For the interpreter (and other code blobs) it is on the
// stack relative to the frame pointer.
if (blob_name == "nmethod")
methodPtr = @cast(blob, "nmethod",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_method
else
methodPtr = user_long(fp + (-3 * ptr_size)) & ptr_mask
// The java class is the holder of the constants (strings)
// that describe the method and signature. This constant pool
// contains symbolic information that describe the properties
// of the class. The indexes for methods and signaturates in
// the constant pool are Symbols that contain utf8
// strings (plus lenghts). (We could also sanity check that
// the tag value is correct [CONSTANT_String = 8]).
// Note that the class name uses '/' instead of '.' as
// package name separator and that the method signature is
// encoded as a method descriptor string. Both of which we
// don't demangle here.
constMethod = @cast(methodPtr, "Method",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_constMethod;
constantPool = @cast(constMethod, "ConstMethod",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_constants;
constantPool_base = constantPool + constantPool_size;
klass = @cast(constantPool, "ConstantPool",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_pool_holder;
klassSymbol = @cast(klass, "Klass",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_name;
klassName = &@cast(klassSymbol, "Symbol",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_body[0];
klassLength = @cast(klassSymbol, "Symbol",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_length;
methodIndex = @cast(constMethod, "ConstMethod",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_name_index;
methodSymbol = user_long(constantPool_base + (methodIndex * ptr_size));
methodName = &@cast(methodSymbol, "Symbol",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_body[0];
methodLength = @cast(methodSymbol, "Symbol",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_length;
if (log_sig)
{
sigIndex = @cast(constMethod, "ConstMethod",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_signature_index;
sigSymbol = user_long(constantPool_base
+ (sigIndex * ptr_size));
sigName = &@cast(sigSymbol, "Symbol",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_body[0];
sigLength = @cast(sigSymbol, "Symbol",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_length;
sig = user_string_n(sigName, sigLength);
}
else
sig = "";
code_name = (log_native
? sprintf("<%s@0x%x>",
str_replace(blob_name, " ", "_"), pc)
: "");
frame = sprintf("%s.%s%s%s",
user_string_n(klassName, klassLength),
user_string_n(methodName, methodLength),
sig, code_name);
// We cannot trust the frame pointer of compiled methods.
// The server (c2) jit compiler uses the fp register.
// We do know the method frame size on the stack. But
// this seems to be useful only as a hint of the minimum
// stack being used.
if (blob_name == "nmethod")
{
trust_fp = 0;
frame_size = @cast(blob, "CodeBlob",
"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.432.b06-2.el8.x86_64/lib/server/libjvm.so")->_frame_size;
}
}
catch
{
// Some assumption above totally failed and we got an address
// read error. Give up and mark frame pointer as suspect.
frame = sprintf("<unknown_frame@0x%x>", pc);
trust_fp = 0;
}
}
else
{
// "Normal" hotspot code. Just print what usymname() gets us.
// All such code is compiled with -fno-omit-frame-pointer so
// we can use that to get at the next frame.
// Theoretically there could be libraries or jni code not
// compiled with -fno-omit-frame-pointer, then we should really
// use the dwarf unwinder or some stack crawling heuristics.
if (log_native)
frame = usymname(pc);
}
// Get next frame by assuming frame pointers are being used.
// (which is not always true for c2 (server) compiled nmethods).
old_fp = fp;
old_sp = sp
%(arch == "powerpc" %?
sp = user_long(sp);
fp = sp + 72; /* fp + (-3 * ptr_size) = 48, parameter save area offset */
pc = link;
link = user_long(sp + 16);
trust_fp = 1; /* We don't need to recover the frame pointer. */
%:
sp = fp;
fp = user_long(sp);
pc = user_long(fp + ptr_size);
%)
// Do we need to double check? We do not want to do this
// unless necessary. We have to assume most code is "sane"
// and has fp setup correctly because we do not have good
// heuristics that cover all cases (native code, interpreted
// code, client code, codeblob stubs). So we only check and try
// to adapt for nmethods. Scanning the stack for plausible
// looking fp and pc values might make us skip a frame.
if (!trust_fp)
{
max_stack_scan = 96; // Arbitrary limit
// Note that first while iteration actually checks that
// the fp and pc from trusting the old fp might be correct
// (it often is if the nmethod come from the client compiler).
// The only validly looking pc values that we know of are in
// the CodeCache (so, we might be skipping native frames).
// The nmethod has a frame_size which gives a hint as to
// how much stack we have to skip at least.
i = 1;
while (i < max_stack_scan
&& (CodeCache_low > pc
|| pc >= CodeCache_high
|| fp <= old_fp))
{
sp = old_sp + ((frame_size + i) * ptr_size);
fp = user_long(sp);
pc = user_long(fp + ptr_size);
i++;
}
if (i == max_stack_scan)
{
if (! print_frames)
frames = frames . " <stack_lost>"
else
log("<stack_lost>")
pc = 0;
}
}
if (frame != "")
{
if (! print_frames)
{
space = (depth != 0) ? " " : "";
frames = frames . space . frame;
}
else
log (frame);
depth++;
}
}
if (depth == max_depth)
{
frame = "<stack_truncated>";
if (! print_frames)
frames = frames . " " . frame
else
log (frame);
}
return frames;
}
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