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[Bug backtrace/14550] New: Loading a custom JIT reader plugincrashes GDB during backtrace
- From: "sanjoy at playingwithpointers dot com"<sourceware-bugzilla at sourceware dot org>
- To: gdb-prs at sourceware dot org
- Date: Thu, 06 Sep 2012 09:29:34 +0000
- Subject: [Bug backtrace/14550] New: Loading a custom JIT reader plugincrashes GDB during backtrace
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=14550
Bug #: 14550
Summary: Loading a custom JIT reader plugin crashes GDB during
backtrace
Product: gdb
Version: unknown
Status: NEW
Severity: normal
Priority: P2
Component: backtrace
AssignedTo: sanjoy@playingwithpointers.com
ReportedBy: sanjoy@playingwithpointers.com
Classification: Unclassified
Sample code (from Michael Haupt <michael.haupt@oracle.com> with minor
modifications):
To crash GDB, jit-reader-load myreader.c and break inside the `func` function
in jithost.c
myreader.c:
#include "gdb/jit-reader.h"
GDB_DECLARE_GPL_COMPATIBLE_READER;
static enum gdb_status read_debug_info(struct gdb_reader_funcs* self,
struct gdb_symbol_callbacks* cbs,
void* memory, long memory_sz) {
GDB_CORE_ADDR* buf = (GDB_CORE_ADDR*) memory;
GDB_CORE_ADDR start = buf[0];
GDB_CORE_ADDR end = buf[1];
struct gdb_object* object = cbs->object_open(cbs);
struct gdb_symtab* symtab = cbs->symtab_open(cbs, object, "");
struct gdb_block* block = cbs->block_open(cbs, symtab, NULL, start, end,
"fluffy");
cbs->symtab_close(cbs, symtab);
cbs->object_close(cbs, object);
return GDB_SUCCESS;
}
enum gdb_status unwind_frame(struct gdb_reader_funcs* self,
struct gdb_unwind_callbacks* cbs) {
return GDB_SUCCESS;
}
struct gdb_frame_id get_frame_id(struct gdb_reader_funcs* self,
struct gdb_unwind_callbacks* cbs) {
struct gdb_frame_id frame = { 0x602000, 0 };
return frame;
}
void destroy_reader(struct gdb_reader_funcs* self) { }
extern struct gdb_reader_funcs* gdb_init_reader(void) {
static struct gdb_reader_funcs funcs = {
GDB_READER_INTERFACE_VERSION,
NULL,
read_debug_info,
unwind_frame,
get_frame_id,
destroy_reader
};
return &funcs;
}
jithost.c:
#include <stdio.h>
#include <sys/mman.h>
#include "gdb/jit-reader.h"
#include "defs.h"
#include "jit.h"
struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
struct jit_code_entry entry = { 0, 0, 0, 0 };
typedef void (*func)();
void __attribute__((noinline)) __jit_debug_register_code() {
__asm("");
}
#define SIZE 4096
int main(int argc, char** argv) {
char* code = (char*) valloc(SIZE);
GDB_CORE_ADDR* buffer = (GDB_CORE_ADDR*) valloc(SIZE);
fprintf(stderr, "buffer at %p, code at %p\n", buffer, code);
if (0 != mprotect(code, SIZE, PROT_WRITE | PROT_READ | PROT_EXEC)) {
perror(NULL);
exit(3);
}
code[0] = 0xc3; // RET
buffer[0] = (GDB_CORE_ADDR) code; // store code address in buffer
buffer[1] = (GDB_CORE_ADDR) (code + 1); // and the end of the generated
"function"
entry.symfile_addr = (GDB_CORE_ADDR) buffer;
entry.symfile_size = SIZE;
__jit_debug_descriptor.first_entry =
__jit_debug_descriptor.relevant_entry = (GDB_CORE_ADDR) &entry;
__jit_debug_descriptor.action_flag = JIT_REGISTER;
__jit_debug_descriptor.version = 1;
__jit_debug_register_code();
(((func)(code)))();
return 0;
}
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