[PATCH v4][makedumpfile 4/7] Implement kernel module's kallsyms resolving

[Stephen Brennan]

Tao Liu <ltao at redhat.com> writes:

> With kernel's kallsyms and btf ready, we can get any kernel types and
> symbol addresses. So we can iterate kernel modules' linked list, and
> parse each one of kernel module's structure to get its kallsyms data.
> At this time, kernel modules' kallsyms symbol defined within .init_ksyms
> section will be resolved.
>
> Suggested-by: Stephen Brennan <stephen.s.brennan at oracle.com>
> Signed-off-by: Tao Liu <ltao at redhat.com>

Reviewed-by: Stephen Brennan <stephen.s.brennan at oracle.com>

> ---
>  kallsyms.c | 125 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  kallsyms.h |   3 ++
>  2 files changed, 127 insertions(+), 1 deletion(-)
>
> diff --git a/kallsyms.c b/kallsyms.c
> index f7737cb..f07b0ee 100644
> --- a/kallsyms.c
> +++ b/kallsyms.c
> @@ -3,6 +3,7 @@
>  #include <string.h>
>  #include "makedumpfile.h"
>  #include "kallsyms.h"
> +#include "btf_info.h"
>  
>  static uint32_t *kallsyms_offsets = NULL;
>  static uint16_t *kallsyms_token_index = NULL;
> @@ -347,4 +348,126 @@ out:
>  		kallsyms_names = NULL;
>  	}
>  	return ret;
> -}
> \ No newline at end of file
> +}
> +
> +INIT_KERN_SYM(modules);
> +
> +INIT_KERN_STRUCT_MEMBER(list_head, next);
> +INIT_KERN_STRUCT_MEMBER(module, list);
> +INIT_KERN_STRUCT_MEMBER(module, name);
> +INIT_KERN_STRUCT_MEMBER(module, core_kallsyms);
> +INIT_KERN_STRUCT_MEMBER(mod_kallsyms, symtab);
> +INIT_KERN_STRUCT_MEMBER(mod_kallsyms, num_symtab);
> +INIT_KERN_STRUCT_MEMBER(mod_kallsyms, strtab);
> +INIT_KERN_STRUCT_MEMBER(elf64_sym, st_name);
> +INIT_KERN_STRUCT_MEMBER(elf64_sym, st_value);
> +
> +#define MEMBER_OFF(S, M) \
> +	GET_KERN_STRUCT_MEMBER_MOFF(S, M) / 8
> +
> +uint64_t next_list(uint64_t list)
> +{
> +	uint64_t next = 0;
> +
> +	readmem(VADDR, list + MEMBER_OFF(list_head, next),
> +		&next, GET_KERN_STRUCT_MEMBER_MSIZE(list_head, next));
> +	return next;
> +}
> +
> +bool init_module_kallsyms(void)
> +{
> +	uint64_t modules, list, value = 0, symtab = 0, strtab = 0;
> +	uint32_t st_name = 0;
> +	int num_symtab, i, j;
> +	struct ksym_info **p;
> +	char symname[512], ch;
> +	char *modname = NULL;
> +	bool ret = false;
> +
> +	modules = GET_KERN_SYM(modules);
> +	if (!KERN_SYM_EXIST(modules)) {
> +		/* Not a failure if no module enabled */
> +		ret = true;
> +		goto out;
> +	}
> +
> +	if (!KERN_STRUCT_MEMBER_EXIST(list_head, next) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(module, list) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(module, name) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(module, core_kallsyms) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(mod_kallsyms, symtab) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(mod_kallsyms, num_symtab) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(mod_kallsyms, strtab) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(elf64_sym, st_name) ||
> +	    !KERN_STRUCT_MEMBER_EXIST(elf64_sym, st_value)) {
> +		/* Fail when module enabled but any required types not found */
> +		fprintf(stderr, "%s: Missing required module syms/types!", __func__);
> +		goto out;
> +	}
> +
> +	modname = (char *)malloc(GET_KERN_STRUCT_MEMBER_MSIZE(module, name));
> +	if (!modname)
> +		goto no_mem;
> +
> +	for (list = next_list(modules); list != modules; list = next_list(list)) {
> +		readmem(VADDR, list - MEMBER_OFF(module, list) +
> +				MEMBER_OFF(module, name),
> +			modname, GET_KERN_STRUCT_MEMBER_MSIZE(module, name));
> +		if (!check_ksyms_require_modname(modname, NULL))
> +			continue;
> +		readmem(VADDR, list - MEMBER_OFF(module, list) +
> +				MEMBER_OFF(module, core_kallsyms) +
> +				MEMBER_OFF(mod_kallsyms, num_symtab),
> +			&num_symtab, GET_KERN_STRUCT_MEMBER_MSIZE(mod_kallsyms, num_symtab));
> +		readmem(VADDR, list - MEMBER_OFF(module, list) +
> +				MEMBER_OFF(module, core_kallsyms) +
> +				MEMBER_OFF(mod_kallsyms, symtab),
> +			&symtab, GET_KERN_STRUCT_MEMBER_MSIZE(mod_kallsyms, symtab));
> +		readmem(VADDR, list - MEMBER_OFF(module, list) +
> +				MEMBER_OFF(module, core_kallsyms) +
> +				MEMBER_OFF(mod_kallsyms, strtab),
> +			&strtab, GET_KERN_STRUCT_MEMBER_MSIZE(mod_kallsyms, strtab));
> +		for (i = 0; i < num_symtab; i++) {
> +			j = 0;
> +			readmem(VADDR, symtab + i * GET_KERN_STRUCT_MEMBER_SSIZE(elf64_sym, st_value) +
> +					MEMBER_OFF(elf64_sym, st_value),
> +				&value, GET_KERN_STRUCT_MEMBER_MSIZE(elf64_sym, st_value));
> +			readmem(VADDR, symtab + i * GET_KERN_STRUCT_MEMBER_SSIZE(elf64_sym, st_name) +
> +					MEMBER_OFF(elf64_sym, st_name),
> +				&st_name, GET_KERN_STRUCT_MEMBER_MSIZE(elf64_sym, st_name));
> +			do {
> +				readmem(VADDR, strtab + st_name + j++, &ch, 1);
> +			} while (ch != '\0');
> +			if (j == 1 || j > sizeof(symname))
> +				/* Skip empty or too long string */
> +				continue;
> +			readmem(VADDR, strtab + st_name, symname, j);
> +
> +			for (j = 0; j < sr_len; j++) {
> +				for (p = (struct ksym_info **)(sr[j]->start);
> +				     p < (struct ksym_info **)(sr[j]->stop);
> +				     p++) {
> +					if (!strcmp((*p)->modname, modname) &&
> +					    !strcmp((*p)->symname, symname)) {
> +						(*p)->value = value;
> +						(*p)->index = i;
> +					}
> +				}
> +			}
> +		}
> +	}
> +	ret = true;
> +	goto out;
> +no_mem:
> +	fprintf(stderr, "%s: Not enough memory!\n", __func__);
> +out:
> +	if (modname)
> +		free(modname);
> +	return ret;
> +}
> +
> +void cleanup_kallsyms(void)
> +{
> +	cleanup_ksyms_section_range();
> +	cleanup_ksyms_modname();
> +}
> diff --git a/kallsyms.h b/kallsyms.h
> index 3791284..897bcdd 100644
> --- a/kallsyms.h
> +++ b/kallsyms.h
> @@ -88,4 +88,7 @@ bool check_ksyms_require_modname(char *modname, int *total);
>  bool register_ksym_section(char *start, char *stop);
>  bool read_vmcoreinfo_kallsyms(void);
>  bool init_kernel_kallsyms(void);
> +uint64_t next_list(uint64_t list);
> +bool init_module_kallsyms(void);
> +void cleanup_kallsyms(void);
>  #endif /* _KALLSYMS_H */
> \ No newline at end of file
> -- 
> 2.47.0