// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <linux/string.h>
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <err.h>
#include <jvmti.h>
#ifdef HAVE_JVMTI_CMLR
#include <jvmticmlr.h>
#endif
#include <limits.h>

#include "jvmti_agent.h"

static int has_line_numbers;
void *jvmti_agent;

static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
{
        char *err_msg = NULL;
        jvmtiError err;
        err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
        if (err == JVMTI_ERROR_NONE) {
                warnx("%s failed with %s", msg, err_msg);
                (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
        } else {
                warnx("%s failed with an unknown error %d", msg, ret);
        }
}

#ifdef HAVE_JVMTI_CMLR
static jvmtiError
do_get_line_number(jvmtiEnv *jvmti, void *pc, jmethodID m, jint bci,
                   jvmti_line_info_t *tab)
{
        jint i, nr_lines = 0;
        jvmtiLineNumberEntry *loc_tab = NULL;
        jvmtiError ret;
        jint src_line = -1;

        ret = (*jvmti)->GetLineNumberTable(jvmti, m, &nr_lines, &loc_tab);
        if (ret == JVMTI_ERROR_ABSENT_INFORMATION || ret == JVMTI_ERROR_NATIVE_METHOD) {
                /* No debug information for this method */
                return ret;
        } else if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetLineNumberTable", ret);
                return ret;
        }

        for (i = 0; i < nr_lines && loc_tab[i].start_location <= bci; i++) {
                src_line = i;
        }

        if (src_line != -1) {
                tab->pc = (unsigned long)pc;
                tab->line_number = loc_tab[src_line].line_number;
                tab->discrim = 0; /* not yet used */
                tab->methodID = m;

                ret = JVMTI_ERROR_NONE;
        } else {
                ret = JVMTI_ERROR_ABSENT_INFORMATION;
        }

        (*jvmti)->Deallocate(jvmti, (unsigned char *)loc_tab);

        return ret;
}

static jvmtiError
get_line_numbers(jvmtiEnv *jvmti, const void *compile_info, jvmti_line_info_t **tab, int *nr_lines)
{
        const jvmtiCompiledMethodLoadRecordHeader *hdr;
        jvmtiCompiledMethodLoadInlineRecord *rec;
        PCStackInfo *c;
        jint ret;
        int nr_total = 0;
        int i, lines_total = 0;

        if (!(tab && nr_lines))
                return JVMTI_ERROR_NULL_POINTER;

        /*
         * Phase 1 -- get the number of lines necessary
         */
        for (hdr = compile_info; hdr != NULL; hdr = hdr->next) {
                if (hdr->kind == JVMTI_CMLR_INLINE_INFO) {
                        rec = (jvmtiCompiledMethodLoadInlineRecord *)hdr;
                        nr_total += rec->numpcs;
                }
        }

        if (nr_total == 0)
                return JVMTI_ERROR_NOT_FOUND;

        /*
         * Phase 2 -- allocate big enough line table
         */
        *tab = malloc(nr_total * sizeof(**tab));
        if (!*tab)
                return JVMTI_ERROR_OUT_OF_MEMORY;

        for (hdr = compile_info; hdr != NULL; hdr = hdr->next) {
                if (hdr->kind == JVMTI_CMLR_INLINE_INFO) {
                        rec = (jvmtiCompiledMethodLoadInlineRecord *)hdr;
                        for (i = 0; i < rec->numpcs; i++) {
                                c = rec->pcinfo + i;
                                /*
                                 * c->methods is the stack of inlined method calls
                                 * at c->pc. [0] is the leaf method. Caller frames
                                 * are ignored at the moment.
                                 */
                                ret = do_get_line_number(jvmti, c->pc,
                                                         c->methods[0],
                                                         c->bcis[0],
                                                         *tab + lines_total);
                                if (ret == JVMTI_ERROR_NONE)
                                        lines_total++;
                        }
                }
        }
        *nr_lines = lines_total;
        return JVMTI_ERROR_NONE;
}
#else /* HAVE_JVMTI_CMLR */

static jvmtiError
get_line_numbers(jvmtiEnv *jvmti __maybe_unused, const void *compile_info __maybe_unused,
                 jvmti_line_info_t **tab __maybe_unused, int *nr_lines __maybe_unused)
{
        return JVMTI_ERROR_NONE;
}
#endif /* HAVE_JVMTI_CMLR */

static void
copy_class_filename(const char * class_sign, const char * file_name, char * result, size_t max_length)
{
        /*
        * Assume path name is class hierarchy, this is a common practice with Java programs
        */
        if (*class_sign == 'L') {
                size_t j, i = 0;
                const char *p = strrchr(class_sign, '/');
                if (p) {
                        /* drop the 'L' prefix and copy up to the final '/' */
                        for (i = 0; i < (size_t)(p - class_sign); i++)
                                result[i] = class_sign[i+1];
                }
                /*
                * append file name, we use loops and not string ops to avoid modifying
                * class_sign which is used later for the symbol name
                */
                for (j = 0; i < (max_length - 1) && file_name && j < strlen(file_name); j++, i++)
                        result[i] = file_name[j];

                result[i] = '\0';
        } else {
                /* fallback case */
                strlcpy(result, file_name, max_length);
        }
}

static jvmtiError
get_source_filename(jvmtiEnv *jvmti, jmethodID methodID, char ** buffer)
{
        jvmtiError ret;
        jclass decl_class;
        char *file_name = NULL;
        char *class_sign = NULL;
        char fn[PATH_MAX];
        size_t len;

        ret = (*jvmti)->GetMethodDeclaringClass(jvmti, methodID, &decl_class);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetMethodDeclaringClass", ret);
                return ret;
        }

        ret = (*jvmti)->GetSourceFileName(jvmti, decl_class, &file_name);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetSourceFileName", ret);
                return ret;
        }

        ret = (*jvmti)->GetClassSignature(jvmti, decl_class, &class_sign, NULL);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetClassSignature", ret);
                goto free_file_name_error;
        }

        copy_class_filename(class_sign, file_name, fn, PATH_MAX);
        len = strlen(fn);
        *buffer = malloc((len + 1) * sizeof(char));
        if (!*buffer) {
                print_error(jvmti, "GetClassSignature", ret);
                ret = JVMTI_ERROR_OUT_OF_MEMORY;
                goto free_class_sign_error;
        }
        strcpy(*buffer, fn);
        ret = JVMTI_ERROR_NONE;

free_class_sign_error:
        (*jvmti)->Deallocate(jvmti, (unsigned char *)class_sign);
free_file_name_error:
        (*jvmti)->Deallocate(jvmti, (unsigned char *)file_name);

        return ret;
}

static jvmtiError
fill_source_filenames(jvmtiEnv *jvmti, int nr_lines,
                      const jvmti_line_info_t * line_tab,
                      char ** file_names)
{
        int index;
        jvmtiError ret;

        for (index = 0; index < nr_lines; ++index) {
                ret = get_source_filename(jvmti, line_tab[index].methodID, &(file_names[index]));
                if (ret != JVMTI_ERROR_NONE)
                        return ret;
        }

        return JVMTI_ERROR_NONE;
}

static void JNICALL
compiled_method_load_cb(jvmtiEnv *jvmti,
                        jmethodID method,
                        jint code_size,
                        void const *code_addr,
                        jint map_length,
                        jvmtiAddrLocationMap const *map,
                        const void *compile_info)
{
        jvmti_line_info_t *line_tab = NULL;
        char ** line_file_names = NULL;
        jclass decl_class;
        char *class_sign = NULL;
        char *func_name = NULL;
        char *func_sign = NULL;
        uint64_t addr = (uint64_t)(uintptr_t)code_addr;
        jvmtiError ret;
        int nr_lines = 0; /* in line_tab[] */
        size_t len;
        int output_debug_info = 0;

        ret = (*jvmti)->GetMethodDeclaringClass(jvmti, method,
                                                &decl_class);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetMethodDeclaringClass", ret);
                return;
        }

        if (has_line_numbers && map && map_length) {
                ret = get_line_numbers(jvmti, compile_info, &line_tab, &nr_lines);
                if (ret != JVMTI_ERROR_NONE) {
                        if (ret != JVMTI_ERROR_NOT_FOUND) {
                                warnx("jvmti: cannot get line table for method");
                        }
                        nr_lines = 0;
                } else if (nr_lines > 0) {
                        line_file_names = malloc(sizeof(char*) * nr_lines);
                        if (!line_file_names) {
                                warnx("jvmti: cannot allocate space for line table method names");
                        } else {
                                memset(line_file_names, 0, sizeof(char*) * nr_lines);
                                ret = fill_source_filenames(jvmti, nr_lines, line_tab, line_file_names);
                                if (ret != JVMTI_ERROR_NONE) {
                                        warnx("jvmti: fill_source_filenames failed");
                                } else {
                                        output_debug_info = 1;
                                }
                        }
                }
        }

        ret = (*jvmti)->GetClassSignature(jvmti, decl_class,
                                          &class_sign, NULL);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetClassSignature", ret);
                goto error;
        }

        ret = (*jvmti)->GetMethodName(jvmti, method, &func_name,
                                      &func_sign, NULL);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "GetMethodName", ret);
                goto error;
        }

        /*
         * write source line info record if we have it
         */
        if (output_debug_info)
                if (jvmti_write_debug_info(jvmti_agent, addr, nr_lines, line_tab, (const char * const *) line_file_names))
                        warnx("jvmti: write_debug_info() failed");

        len = strlen(func_name) + strlen(class_sign) + strlen(func_sign) + 2;
        {
                char str[len];
                snprintf(str, len, "%s%s%s", class_sign, func_name, func_sign);

                if (jvmti_write_code(jvmti_agent, str, addr, code_addr, code_size))
                        warnx("jvmti: write_code() failed");
        }
error:
        (*jvmti)->Deallocate(jvmti, (unsigned char *)func_name);
        (*jvmti)->Deallocate(jvmti, (unsigned char *)func_sign);
        (*jvmti)->Deallocate(jvmti, (unsigned char *)class_sign);
        free(line_tab);
        while (line_file_names && (nr_lines > 0)) {
            if (line_file_names[nr_lines - 1]) {
                free(line_file_names[nr_lines - 1]);
            }
            nr_lines -= 1;
        }
        free(line_file_names);
}

static void JNICALL
code_generated_cb(jvmtiEnv *jvmti,
                  char const *name,
                  void const *code_addr,
                  jint code_size)
{
        uint64_t addr = (uint64_t)(unsigned long)code_addr;
        int ret;

        ret = jvmti_write_code(jvmti_agent, name, addr, code_addr, code_size);
        if (ret)
                warnx("jvmti: write_code() failed for code_generated");
}

JNIEXPORT jint JNICALL
Agent_OnLoad(JavaVM *jvm, char *options, void *reserved __maybe_unused)
{
        jvmtiEventCallbacks cb;
        jvmtiCapabilities caps1;
        jvmtiJlocationFormat format;
        jvmtiEnv *jvmti = NULL;
        jint ret;

        jvmti_agent = jvmti_open();
        if (!jvmti_agent) {
                warnx("jvmti: open_agent failed");
                return -1;
        }

        /*
         * Request a JVMTI interface version 1 environment
         */
        ret = (*jvm)->GetEnv(jvm, (void *)&jvmti, JVMTI_VERSION_1);
        if (ret != JNI_OK) {
                warnx("jvmti: jvmti version 1 not supported");
                return -1;
        }

        /*
         * acquire method_load capability, we require it
         * request line numbers (optional)
         */
        memset(&caps1, 0, sizeof(caps1));
        caps1.can_generate_compiled_method_load_events = 1;

        ret = (*jvmti)->AddCapabilities(jvmti, &caps1);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "AddCapabilities", ret);
                return -1;
        }
        ret = (*jvmti)->GetJLocationFormat(jvmti, &format);
        if (ret == JVMTI_ERROR_NONE && format == JVMTI_JLOCATION_JVMBCI) {
                memset(&caps1, 0, sizeof(caps1));
                caps1.can_get_line_numbers = 1;
                caps1.can_get_source_file_name = 1;
                ret = (*jvmti)->AddCapabilities(jvmti, &caps1);
                if (ret == JVMTI_ERROR_NONE)
                        has_line_numbers = 1;
        } else if (ret != JVMTI_ERROR_NONE)
                print_error(jvmti, "GetJLocationFormat", ret);


        memset(&cb, 0, sizeof(cb));

        cb.CompiledMethodLoad   = compiled_method_load_cb;
        cb.DynamicCodeGenerated = code_generated_cb;

        ret = (*jvmti)->SetEventCallbacks(jvmti, &cb, sizeof(cb));
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "SetEventCallbacks", ret);
                return -1;
        }

        ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
                        JVMTI_EVENT_COMPILED_METHOD_LOAD, NULL);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "SetEventNotificationMode(METHOD_LOAD)", ret);
                return -1;
        }

        ret = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
                        JVMTI_EVENT_DYNAMIC_CODE_GENERATED, NULL);
        if (ret != JVMTI_ERROR_NONE) {
                print_error(jvmti, "SetEventNotificationMode(CODE_GENERATED)", ret);
                return -1;
        }
        return 0;
}

JNIEXPORT void JNICALL
Agent_OnUnload(JavaVM *jvm __maybe_unused)
{
        int ret;

        ret = jvmti_close(jvmti_agent);
        if (ret)
                errx(1, "Error: op_close_agent()");
}