diff options
Diffstat (limited to 'libctf')
| -rw-r--r-- | libctf/ChangeLog | 14 | ||||
| -rw-r--r-- | libctf/ctf-impl.h | 1 | ||||
| -rw-r--r-- | libctf/ctf-link.c | 660 | ||||
| -rw-r--r-- | libctf/ctf-util.c | 20 |
4 files changed, 693 insertions, 2 deletions
diff --git a/libctf/ChangeLog b/libctf/ChangeLog index 4ec7442..803e8de 100644 --- a/libctf/ChangeLog +++ b/libctf/ChangeLog @@ -1,5 +1,19 @@ 2020-07-22 Nick Alcock <nick.alcock@oracle.com> + * ctf-impl.h (ctf_list_splice): New. + * ctf-util.h (ctf_list_splice): Likewise. + * ctf-link.c (link_sort_inputs_cb_arg_t): Likewise. + (ctf_link_sort_inputs): Likewise. + (ctf_link_deduplicating_count_inputs): Likewise. + (ctf_link_deduplicating_open_inputs): Likewise. + (ctf_link_deduplicating_close_inputs): Likewise. + (ctf_link_deduplicating_variables): Likewise. + (ctf_link_deduplicating_per_cu): Likewise. + (ctf_link_deduplicating): Likewise. + (ctf_link): Call it. + +2020-07-22 Nick Alcock <nick.alcock@oracle.com> + * ctf-link.c (ctf_link_one_input_archive_member): Check CTF_LINK_OMIT_VARIABLES_SECTION. diff --git a/libctf/ctf-impl.h b/libctf/ctf-impl.h index a8a16f7..35320d4 100644 --- a/libctf/ctf-impl.h +++ b/libctf/ctf-impl.h @@ -629,6 +629,7 @@ extern char *ctf_sha1_fini (ctf_sha1_t *, char *); extern void ctf_list_append (ctf_list_t *, void *); extern void ctf_list_prepend (ctf_list_t *, void *); extern void ctf_list_delete (ctf_list_t *, void *); +extern void ctf_list_splice (ctf_list_t *, ctf_list_t *); extern int ctf_list_empty_p (ctf_list_t *lp); extern int ctf_dtd_insert (ctf_file_t *, ctf_dtdef_t *, int flag, int kind); diff --git a/libctf/ctf-link.c b/libctf/ctf-link.c index 043d6a2..f269fe7 100644 --- a/libctf/ctf-link.c +++ b/libctf/ctf-link.c @@ -819,6 +819,659 @@ ctf_link_one_input_archive (void *key, void *value, void *arg_) ctf_link_close_one_input_archive (key, value, NULL); } +typedef struct link_sort_inputs_cb_arg +{ + int is_cu_mapped; + ctf_file_t *fp; +} link_sort_inputs_cb_arg_t; + +/* Sort the inputs by N (the link order). For CU-mapped links, this is a + mapping of input to output name, not a mapping of input name to input + ctf_link_input_t: compensate accordingly. */ +static int +ctf_link_sort_inputs (const ctf_next_hkv_t *one, const ctf_next_hkv_t *two, + void *arg) +{ + ctf_link_input_t *input_1; + ctf_link_input_t *input_2; + link_sort_inputs_cb_arg_t *cu_mapped = (link_sort_inputs_cb_arg_t *) arg; + + if (!cu_mapped || !cu_mapped->is_cu_mapped) + { + input_1 = (ctf_link_input_t *) one->hkv_value; + input_2 = (ctf_link_input_t *) two->hkv_value; + } + else + { + const char *name_1 = (const char *) one->hkv_key; + const char *name_2 = (const char *) two->hkv_key; + + input_1 = ctf_dynhash_lookup (cu_mapped->fp->ctf_link_inputs, name_1); + input_2 = ctf_dynhash_lookup (cu_mapped->fp->ctf_link_inputs, name_2); + + /* There is no guarantee that CU-mappings actually have corresponding + inputs: the relative ordering in that case is unimportant. */ + if (!input_1) + return -1; + if (!input_2) + return 1; + } + + if (input_1->n < input_2->n) + return -1; + else if (input_1->n > input_2->n) + return 1; + else + return 0; +} + +/* Count the number of input dicts in the ctf_link_inputs, or that subset of the + ctf_link_inputs given by CU_NAMES if set. Return the number of input dicts, + and optionally the name and ctf_link_input_t of the single input archive if + only one exists (no matter how many dicts it contains). */ +static ssize_t +ctf_link_deduplicating_count_inputs (ctf_file_t *fp, ctf_dynhash_t *cu_names, + ctf_link_input_t **only_one_input) +{ + ctf_dynhash_t *inputs = fp->ctf_link_inputs; + ctf_next_t *i = NULL; + void *name, *input; + ctf_link_input_t *one_input = NULL; + const char *one_name = NULL; + ssize_t count = 0, narcs = 0; + int err; + + if (cu_names) + inputs = cu_names; + + while ((err = ctf_dynhash_next (inputs, &i, &name, &input)) == 0) + { + ssize_t one_count; + + one_name = (const char *) name; + /* If we are processing CU names, get the real input. */ + if (cu_names) + one_input = ctf_dynhash_lookup (fp->ctf_link_inputs, one_name); + else + one_input = (ctf_link_input_t *) input; + + if (!one_input) + continue; + + one_count = ctf_link_lazy_open (fp, one_input); + + if (one_count < 0) + { + ctf_next_destroy (i); + return -1; /* errno is set for us. */ + } + + count += one_count; + narcs++; + } + if (err != ECTF_NEXT_END) + { + ctf_err_warn (fp, 0, "Iteration error counting deduplicating CTF link " + "inputs: %s", ctf_errmsg (err)); + ctf_set_errno (fp, err); + return -1; + } + + if (!count) + return 0; + + if (narcs == 1) + { + if (only_one_input) + *only_one_input = one_input; + } + else if (only_one_input) + *only_one_input = NULL; + + return count; +} + +/* Allocate and populate an inputs array big enough for a given set of inputs: + either a specific set of CU names (those from that set found in the + ctf_link_inputs), or the entire ctf_link_inputs (if cu_names is not set). + The number of inputs (from ctf_link_deduplicating_count_inputs, above) is + passed in NINPUTS: an array of uint32_t containing parent pointers + (corresponding to those members of the inputs that have parents) is allocated + and returned in PARENTS. + + The inputs are *archives*, not files: the archive can have multiple members + if it is the result of a previous incremental link. We want to add every one + in turn, including the shared parent. (The dedup machinery knows that a type + used by a single dictionary and its parent should not be shared in + CTF_LINK_SHARE_DUPLICATED mode.) + + If no inputs exist that correspond to these CUs, return NULL with the errno + set to ECTF_NOCTFDATA. */ +static ctf_file_t ** +ctf_link_deduplicating_open_inputs (ctf_file_t *fp, ctf_dynhash_t *cu_names, + ssize_t ninputs, uint32_t **parents) +{ + ctf_dynhash_t *inputs = fp->ctf_link_inputs; + ctf_next_t *i = NULL; + void *name, *input; + link_sort_inputs_cb_arg_t sort_arg; + ctf_file_t **dedup_inputs = NULL; + ctf_file_t **walk; + uint32_t *parents_ = NULL; + int err; + + if (cu_names) + inputs = cu_names; + + if ((dedup_inputs = calloc (ninputs, sizeof (ctf_file_t *))) == NULL) + goto oom; + + if ((parents_ = calloc (ninputs, sizeof (uint32_t))) == NULL) + goto oom; + + walk = dedup_inputs; + + /* Counting done: push every input into the array, in the order they were + passed to ctf_link_add_ctf (and ultimately ld). */ + + sort_arg.is_cu_mapped = (cu_names != NULL); + sort_arg.fp = fp; + + while ((err = ctf_dynhash_next_sorted (inputs, &i, &name, &input, + ctf_link_sort_inputs, &sort_arg)) == 0) + { + const char *one_name = (const char *) name; + ctf_link_input_t *one_input; + ctf_file_t *one_fp; + ctf_file_t *parent_fp = NULL; + uint32_t parent_i; + ctf_next_t *j = NULL; + + /* If we are processing CU names, get the real input. All the inputs + will have been opened, if they contained any CTF at all. */ + if (cu_names) + one_input = ctf_dynhash_lookup (fp->ctf_link_inputs, one_name); + else + one_input = (ctf_link_input_t *) input; + + if (!one_input || (!one_input->clin_arc && !one_input->clin_fp)) + continue; + + /* Short-circuit: if clin_fp is set, just use it. */ + if (one_input->clin_fp) + { + parents_[walk - dedup_inputs] = walk - dedup_inputs; + *walk = one_input->clin_fp; + walk++; + continue; + } + + /* Get and insert the parent archive (if any), if this archive has + multiple members. We assume, as elsewhere, that the parent is named + _CTF_SECTION. */ + + if ((parent_fp = ctf_arc_open_by_name (one_input->clin_arc, + _CTF_SECTION, &err)) == NULL) + { + if (err != ECTF_NOMEMBNAM) + { + ctf_next_destroy (i); + ctf_set_errno (fp, err); + goto err; + } + } + else + { + *walk = parent_fp; + parent_i = walk - dedup_inputs; + walk++; + } + + /* We disregard the input archive name: either it is the parent (which we + already have), or we want to put everything into one TU sharing the + cuname anyway (if this is a CU-mapped link), or this is the final phase + of a relink with CU-mapping off (i.e. ld -r) in which case the cuname + is correctly set regardless. */ + while ((one_fp = ctf_archive_next (one_input->clin_arc, &j, NULL, + 1, &err)) != NULL) + { + if (one_fp->ctf_flags & LCTF_CHILD) + { + /* The contents of the parents array for elements not + corresponding to children is undefined. If there is no parent + (itself a sign of a likely linker bug or corrupt input), we set + it to itself. */ + + ctf_import (one_fp, parent_fp); + if (parent_fp) + parents_[walk - dedup_inputs] = parent_i; + else + parents_[walk - dedup_inputs] = walk - dedup_inputs; + } + *walk = one_fp; + walk++; + } + if (err != ECTF_NEXT_END) + { + ctf_next_destroy (i); + goto iterr; + } + } + if (err != ECTF_NEXT_END) + goto iterr; + + *parents = parents_; + + return dedup_inputs; + + oom: + err = ENOMEM; + + iterr: + ctf_set_errno (fp, err); + + err: + free (dedup_inputs); + free (parents_); + ctf_err_warn (fp, 0, "Error in deduplicating CTF link input allocation: %s", + ctf_errmsg (ctf_errno (fp))); + return NULL; +} + +/* Close INPUTS that have already been linked, first the passed array, and then + that subset of the ctf_link_inputs archives they came from cited by the + CU_NAMES. If CU_NAMES is not specified, close all the ctf_link_inputs in one + go, leaving it empty. */ +static int +ctf_link_deduplicating_close_inputs (ctf_file_t *fp, ctf_dynhash_t *cu_names, + ctf_file_t **inputs, ssize_t ninputs) +{ + ctf_next_t *it = NULL; + void *name; + int err; + ssize_t i; + + /* This is the inverse of ctf_link_deduplicating_open_inputs: so first, close + all the individual input dicts, opened by the archive iterator. */ + for (i = 0; i < ninputs; i++) + ctf_file_close (inputs[i]); + + /* Now close the archives they are part of. */ + if (cu_names) + { + while ((err = ctf_dynhash_next (cu_names, &it, &name, NULL)) == 0) + { + /* Remove the input from the linker inputs, if it exists, which also + closes it. */ + + ctf_dynhash_remove (fp->ctf_link_inputs, (const char *) name); + } + if (err != ECTF_NEXT_END) + { + ctf_err_warn (fp, 0, "Iteration error in deduplicating link input " + "freeing: %s", ctf_errmsg (err)); + ctf_set_errno (fp, err); + } + } + else + ctf_dynhash_empty (fp->ctf_link_inputs); + + return 0; +} + +/* Do a deduplicating link of all variables in the inputs. */ +static int +ctf_link_deduplicating_variables (ctf_file_t *fp, ctf_file_t **inputs, + size_t ninputs, int cu_mapped) +{ + ctf_link_in_member_cb_arg_t arg; + size_t i; + + arg.cu_mapped = cu_mapped; + arg.out_fp = fp; + arg.in_input_cu_file = 0; + + for (i = 0; i < ninputs; i++) + { + arg.in_fp = inputs[i]; + if (ctf_cuname (inputs[i]) != NULL) + arg.in_file_name = ctf_cuname (inputs[i]); + else + arg.in_file_name = "unnamed-CU"; + arg.cu_name = arg.in_file_name; + if (ctf_variable_iter (arg.in_fp, ctf_link_one_variable, &arg) < 0) + return ctf_set_errno (fp, ctf_errno (arg.in_fp)); + + /* Outputs > 0 are per-CU. */ + arg.in_input_cu_file = 1; + } + return 0; +} + +/* Do the per-CU part of a deduplicating link. */ +static int +ctf_link_deduplicating_per_cu (ctf_file_t *fp) +{ + ctf_next_t *i = NULL; + int err; + void *out_cu; + void *in_cus; + + /* Links with a per-CU mapping in force get a first pass of deduplication, + dedupping the inputs for a given CU mapping into the output for that + mapping. The outputs from this process get fed back into the final pass + that is carried out even for non-CU links. */ + + while ((err = ctf_dynhash_next (fp->ctf_link_out_cu_mapping, &i, &out_cu, + &in_cus)) == 0) + { + const char *out_name = (const char *) out_cu; + ctf_dynhash_t *in = (ctf_dynhash_t *) in_cus; + ctf_file_t *out = NULL; + ctf_file_t **inputs; + ctf_file_t **outputs; + ctf_archive_t *in_arc; + ssize_t ninputs; + ctf_link_input_t *only_input; + uint32_t noutputs; + uint32_t *parents; + + if ((ninputs = ctf_link_deduplicating_count_inputs (fp, in, + &only_input)) == -1) + goto err_open_inputs; + + /* CU mapping with no inputs? Skip. */ + if (ninputs == 0) + continue; + + if (labs ((long int) ninputs) > 0xfffffffe) + { + ctf_err_warn (fp, 0, "Too many inputs in deduplicating link: %li", + (long int) ninputs); + goto err_open_inputs; + } + + /* Short-circuit: a cu-mapped link with only one input archive with + unconflicting contents is a do-nothing, and we can just leave the input + in place: we do have to change the cuname, though, so we unwrap it, + change the cuname, then stuff it back in the linker input again, via + the clin_fp short-circuit member. ctf_link_deduplicating_open_inputs + will spot this member and jam it straight into the next link phase, + ignoring the corresponding archive. */ + if (only_input && ninputs == 1) + { + ctf_next_t *ai = NULL; + int err; + + /* We can abuse an archive iterator to get the only member cheaply, no + matter what its name. */ + only_input->clin_fp = ctf_archive_next (only_input->clin_arc, + &ai, NULL, 0, &err); + if (!only_input->clin_fp) + { + ctf_err_warn (fp, 0, "Cannot open archive %s in CU-mapped CTF " + "link: %s", only_input->clin_filename, + ctf_errmsg (err)); + ctf_set_errno (fp, err); + goto err_open_inputs; + } + ctf_next_destroy (ai); + + if (strcmp (only_input->clin_filename, out_name) != 0) + { + /* Renaming. We need to add a new input, then null out the + clin_arc and clin_fp of the old one to stop it being + auto-closed on removal. The new input needs its cuname changed + to out_name, which is doable only because the cuname is a + dynamic property which can be changed even in readonly + dicts. */ + + ctf_cuname_set (only_input->clin_fp, out_name); + if (ctf_link_add_ctf_internal (fp, only_input->clin_arc, + only_input->clin_fp, + out_name) < 0) + { + ctf_err_warn (fp, 0, "Cannot add intermediate files " + "to link: %s", ctf_errmsg (ctf_errno (fp))); + goto err_open_inputs; + } + only_input->clin_arc = NULL; + only_input->clin_fp = NULL; + ctf_dynhash_remove (fp->ctf_link_inputs, + only_input->clin_filename); + } + continue; + } + + /* This is a real CU many-to-one mapping: we must dedup the inputs into + a new output to be used in the final link phase. */ + + if ((inputs = ctf_link_deduplicating_open_inputs (fp, in, ninputs, + &parents)) == NULL) + { + ctf_next_destroy (i); + goto err_inputs; + } + + if ((out = ctf_create (&err)) == NULL) + { + ctf_err_warn (fp, 0, "Cannot create per-CU CTF archive for %s: %s", + out_name, ctf_errmsg (err)); + ctf_set_errno (fp, err); + goto err_inputs; + } + + /* Share the atoms table to reduce memory usage. */ + out->ctf_dedup_atoms = fp->ctf_dedup_atoms_alloc; + + /* No ctf_imports at this stage: this per-CU dictionary has no parents. + Parent/child deduplication happens in the link's final pass. However, + the cuname *is* important, as it is propagated into the final + dictionary. */ + ctf_cuname_set (out, out_name); + + if (ctf_dedup (out, inputs, ninputs, parents, 1) < 0) + { + ctf_err_warn (fp, 0, "CU-mapped deduplication failed for %s: %s", + out_name, ctf_errmsg (ctf_errno (out))); + goto err_inputs; + } + + if ((outputs = ctf_dedup_emit (out, inputs, ninputs, parents, + &noutputs, 1)) == NULL) + { + ctf_err_warn (fp, 0, "CU-mapped deduplicating link type emission " + "failed for %s: %s", out_name, + ctf_errmsg (ctf_errno (out))); + goto err_inputs; + } + if (!ctf_assert (fp, noutputs == 1)) + goto err_inputs_outputs; + + if (!(fp->ctf_link_flags & CTF_LINK_OMIT_VARIABLES_SECTION) + && ctf_link_deduplicating_variables (out, inputs, ninputs, 1) < 0) + { + ctf_err_warn (fp, 0, "CU-mapped deduplicating link variable " + "emission failed for %s: %s", out_name, + ctf_errmsg (ctf_errno (out))); + goto err_inputs_outputs; + } + + if (ctf_link_deduplicating_close_inputs (fp, in, inputs, ninputs) < 0) + { + free (inputs); + free (parents); + goto err_outputs; + } + free (inputs); + free (parents); + + /* Splice any errors or warnings created during this link back into the + dict that the caller knows about. */ + ctf_list_splice (&fp->ctf_errs_warnings, &outputs[0]->ctf_errs_warnings); + + /* This output now becomes an input to the next link phase, with a name + equal to the CU name. We have to wrap it in an archive wrapper + first. */ + + if ((in_arc = ctf_new_archive_internal (0, 0, NULL, outputs[0], NULL, + NULL, &err)) == NULL) + { + ctf_set_errno (fp, err); + goto err_outputs; + } + + if (ctf_link_add_ctf_internal (fp, in_arc, NULL, + ctf_cuname (outputs[0])) < 0) + { + ctf_err_warn (fp, 0, "Cannot add intermediate files to link: %s", + ctf_errmsg (ctf_errno (fp))); + goto err_outputs; + } + + ctf_file_close (out); + free (outputs); + continue; + + err_inputs_outputs: + ctf_list_splice (&fp->ctf_errs_warnings, &outputs[0]->ctf_errs_warnings); + ctf_file_close (outputs[0]); + free (outputs); + err_inputs: + ctf_link_deduplicating_close_inputs (fp, in, inputs, ninputs); + ctf_file_close (out); + free (inputs); + free (parents); + err_open_inputs: + ctf_next_destroy (i); + return -1; + + err_outputs: + ctf_list_splice (&fp->ctf_errs_warnings, &outputs[0]->ctf_errs_warnings); + ctf_file_close (outputs[0]); + free (outputs); + ctf_next_destroy (i); + return -1; /* Errno is set for us. */ + } + if (err != ECTF_NEXT_END) + { + ctf_err_warn (fp, 0, "Iteration error in CU-mapped deduplicating " + "link: %s", ctf_errmsg (err)); + return ctf_set_errno (fp, err); + } + + return 0; +} + +/* Do a deduplicating link using the ctf-dedup machinery. */ +static void +ctf_link_deduplicating (ctf_file_t *fp) +{ + size_t i; + ctf_file_t **inputs, **outputs = NULL; + ssize_t ninputs; + uint32_t noutputs; + uint32_t *parents; + + if (ctf_dedup_atoms_init (fp) < 0) + { + ctf_err_warn (fp, 0, "%s allocating CTF dedup atoms table", + ctf_errmsg (ctf_errno (fp))); + return; /* Errno is set for us. */ + } + + if (fp->ctf_link_out_cu_mapping + && (ctf_link_deduplicating_per_cu (fp) < 0)) + return; /* Errno is set for us. */ + + if ((ninputs = ctf_link_deduplicating_count_inputs (fp, NULL, NULL)) < 0) + return; /* Errno is set for us. */ + + if ((inputs = ctf_link_deduplicating_open_inputs (fp, NULL, ninputs, + &parents)) == NULL) + return; /* Errno is set for us. */ + + if (ninputs == 1 && ctf_cuname (inputs[0]) != NULL) + ctf_cuname_set (fp, ctf_cuname (inputs[0])); + + if (ctf_dedup (fp, inputs, ninputs, parents, 0) < 0) + { + ctf_err_warn (fp, 0, "Deduplication failed for %s: %s", + ctf_link_input_name (fp), ctf_errmsg (ctf_errno (fp))); + goto err; + } + + if ((outputs = ctf_dedup_emit (fp, inputs, ninputs, parents, &noutputs, + 0)) == NULL) + { + ctf_err_warn (fp, 0, "Deduplicating link type emission failed " + "for %s: %s", ctf_link_input_name (fp), + ctf_errmsg (ctf_errno (fp))); + goto err; + } + + if (!ctf_assert (fp, outputs[0] == fp)) + goto err; + + for (i = 0; i < noutputs; i++) + { + char *dynname; + + /* We already have access to this one. Close the duplicate. */ + if (i == 0) + { + ctf_file_close (outputs[0]); + continue; + } + + if ((dynname = strdup (ctf_cuname (outputs[i]))) == NULL) + goto oom_one_output; + + if (ctf_dynhash_insert (fp->ctf_link_outputs, dynname, outputs[i]) < 0) + goto oom_one_output; + + continue; + + oom_one_output: + ctf_err_warn (fp, 0, "Out of memory allocating link outputs"); + ctf_set_errno (fp, ENOMEM); + free (dynname); + + for (; i < noutputs; i++) + ctf_file_close (outputs[i]); + goto err; + } + + if (!(fp->ctf_link_flags & CTF_LINK_OMIT_VARIABLES_SECTION) + && ctf_link_deduplicating_variables (fp, inputs, ninputs, 0) < 0) + { + ctf_err_warn (fp, 0, "Deduplicating link variable emission failed for " + "%s: %s", ctf_link_input_name (fp), + ctf_errmsg (ctf_errno (fp))); + for (i = 1; i < noutputs; i++) + ctf_file_close (outputs[i]); + goto err; + } + + /* Now close all the inputs, including per-CU intermediates. */ + + if (ctf_link_deduplicating_close_inputs (fp, NULL, inputs, ninputs) < 0) + return; /* errno is set for us. */ + + ninputs = 0; /* Prevent double-close. */ + ctf_set_errno (fp, 0); + + /* Fall through. */ + + err: + for (i = 0; i < (size_t) ninputs; i++) + ctf_file_close (inputs[i]); + free (inputs); + free (parents); + free (outputs); + return; +} + /* Merge types and variable sections in all files added to the link together. All the added files are closed. */ int @@ -871,8 +1524,11 @@ ctf_link (ctf_file_t *fp, int flags) } } - ctf_dynhash_iter (fp->ctf_link_inputs, ctf_link_one_input_archive, - &arg); + if ((flags & CTF_LINK_NONDEDUP) || (getenv ("LD_NO_CTF_DEDUP"))) + ctf_dynhash_iter (fp->ctf_link_inputs, ctf_link_one_input_archive, + &arg); + else + ctf_link_deduplicating (fp); /* Discard the now-unnecessary mapping table data from all the outputs. */ if (fp->ctf_link_type_mapping) diff --git a/libctf/ctf-util.c b/libctf/ctf-util.c index c113dfc..a0338f4 100644 --- a/libctf/ctf-util.c +++ b/libctf/ctf-util.c @@ -88,6 +88,26 @@ ctf_list_empty_p (ctf_list_t *lp) return (lp->l_next == NULL && lp->l_prev == NULL); } +/* Splice one entire list onto the end of another one. The existing list is + emptied. */ + +void +ctf_list_splice (ctf_list_t *lp, ctf_list_t *append) +{ + if (ctf_list_empty_p (append)) + return; + + if (lp->l_prev != NULL) + lp->l_prev->l_next = append->l_next; + else + lp->l_next = append->l_next; + + append->l_next->l_prev = lp->l_prev; + lp->l_prev = append->l_prev; + append->l_next = NULL; + append->l_prev = NULL; +} + /* Convert a 32-bit ELF symbol into Elf64 and return a pointer to it. */ Elf64_Sym * |