On Fri, 10 Jul 2020 15:38:41 +0200
Peter Zijlstra <pet...@infradead.org> wrote:
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -16,6 +16,7 @@
>
> #include <linux/hashtable.h>
> #include <linux/kernel.h>
> +#include <linux/static_call_types.h>
>
> #define FAKE_JUMP_OFFSET -1
>
> @@ -433,6 +434,99 @@ static int add_dead_ends(struct objtool_
> return 0;
> }
>
> +static int create_static_call_sections(struct objtool_file *file)
> +{
> + struct section *sec, *reloc_sec;
> + struct reloc *reloc;
> + struct static_call_site *site;
> + struct instruction *insn;
> + struct symbol *key_sym;
> + char *key_name, *tmp;
> + int idx;
> +
> + sec = find_section_by_name(file->elf, ".static_call_sites");
> + if (sec) {
> + INIT_LIST_HEAD(&file->static_call_list);
> + WARN("file already has .static_call_sites section, skipping");
> + return 0;
> + }
> +
> + if (list_empty(&file->static_call_list))
> + return 0;
> +
> + idx = 0;
> + list_for_each_entry(insn, &file->static_call_list, static_call_node)
> + idx++;
> +
> + sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
> + sizeof(struct static_call_site), idx);
> + if (!sec)
> + return -1;
> +
> + reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
> + if (!reloc_sec)
> + return -1;
> +
> + idx = 0;
> + list_for_each_entry(insn, &file->static_call_list, static_call_node) {
> +
> + site = (struct static_call_site *)sec->data->d_buf + idx;
> + memset(site, 0, sizeof(struct static_call_site));
> +
> + /* populate reloc for 'addr' */
> + reloc = malloc(sizeof(*reloc));
> + if (!reloc) {
> + perror("malloc");
> + return -1;
> + }
> + memset(reloc, 0, sizeof(*reloc));
> + reloc->sym = insn->sec->sym;
> + reloc->addend = insn->offset;
> + reloc->type = R_X86_64_PC32;
> + reloc->offset = idx * sizeof(struct static_call_site);
> + reloc->sec = reloc_sec;
> + elf_add_reloc(file->elf, reloc);
> +
> + /* find key symbol */
> + key_name = strdup(insn->call_dest->name);
Should check for failed allocation of strdup().
> + if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
> + strlen(STATIC_CALL_TRAMP_PREFIX_STR))) {
> + WARN("static_call: trampoline name malformed: %s",
> key_name);
> + return -1;
> + }
> + tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN -
> STATIC_CALL_KEY_PREFIX_LEN;
> + memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR,
> STATIC_CALL_KEY_PREFIX_LEN);
> +
> + key_sym = find_symbol_by_name(file->elf, tmp);
> + if (!key_sym) {
> + WARN("static_call: can't find static_call_key symbol:
> %s", tmp);
> + return -1;
> + }
> + free(key_name);
> +
> + /* populate reloc for 'key' */
> + reloc = malloc(sizeof(*reloc));
> + if (!reloc) {
> + perror("malloc");
> + return -1;
> + }
> + memset(reloc, 0, sizeof(*reloc));
> + reloc->sym = key_sym;
> + reloc->addend = 0;
> + reloc->type = R_X86_64_PC32;
How easy would this be for other architectures to implement this? That
is how much of this function is x86 specific?
-- Steve
> + reloc->offset = idx * sizeof(struct static_call_site) + 4;
> + reloc->sec = reloc_sec;
> + elf_add_reloc(file->elf, reloc);
> +
> + idx++;
> + }
> +
> + if (elf_rebuild_reloc_section(file->elf, reloc_sec))
> + return -1;
> +
> + return 0;
> +}
> +
