This looks good to me. Thanks, Jiri.
Acked-by: Hao Luo <haoluo@xxxxxxxxxx>
On Sat, Oct 31, 2020 at 3:31 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Moving find_all_percpu_vars under generic collect_symbols
> function that walks over symbols and calls collect_percpu_var.
>
> We will add another collect function that needs to go through
> all the symbols, so it's better we go through them just once.
>
> There's no functional change intended.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> btf_encoder.c | 124 +++++++++++++++++++++++++++-----------------------
> 1 file changed, 67 insertions(+), 57 deletions(-)
>
> diff --git a/btf_encoder.c b/btf_encoder.c
> index 4c92908beab2..1866bb16a8ba 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -250,75 +250,85 @@ static bool percpu_var_exists(uint64_t addr, uint32_t *sz, const char **name)
> return true;
> }
>
> -static int find_all_percpu_vars(struct btf_elf *btfe)
> +static int collect_percpu_var(struct btf_elf *btfe, GElf_Sym *sym)
> {
> - uint32_t core_id;
> - GElf_Sym sym;
> + const char *sym_name;
> + uint64_t addr;
> + uint32_t size;
>
> - /* cache variables' addresses, preparing for searching in symtab. */
> - percpu_var_cnt = 0;
> + /* compare a symbol's shndx to determine if it's a percpu variable */
> + if (elf_sym__section(sym) != btfe->percpu_shndx)
> + return 0;
> + if (elf_sym__type(sym) != STT_OBJECT)
> + return 0;
>
> - /* search within symtab for percpu variables */
> - elf_symtab__for_each_symbol(btfe->symtab, core_id, sym) {
> - const char *sym_name;
> - uint64_t addr;
> - uint32_t size;
> + addr = elf_sym__value(sym);
> + /*
> + * Store only those symbols that have allocated space in the percpu section.
> + * This excludes the following three types of symbols:
> + *
> + * 1. __ADDRESSABLE(sym), which are forcely emitted as symbols.
> + * 2. __UNIQUE_ID(prefix), which are introduced to generate unique ids.
> + * 3. __exitcall(fn), functions which are labeled as exit calls.
> + *
> + * In addition, the variables defined using DEFINE_PERCPU_FIRST are
> + * also not included, which currently includes:
> + *
> + * 1. fixed_percpu_data
> + */
> + if (!addr)
> + return 0;
>
> - /* compare a symbol's shndx to determine if it's a percpu variable */
> - if (elf_sym__section(&sym) != btfe->percpu_shndx)
> - continue;
> - if (elf_sym__type(&sym) != STT_OBJECT)
> - continue;
> + size = elf_sym__size(sym);
> + if (!size)
> + return 0; /* ignore zero-sized symbols */
>
> - addr = elf_sym__value(&sym);
> - /*
> - * Store only those symbols that have allocated space in the percpu section.
> - * This excludes the following three types of symbols:
> - *
> - * 1. __ADDRESSABLE(sym), which are forcely emitted as symbols.
> - * 2. __UNIQUE_ID(prefix), which are introduced to generate unique ids.
> - * 3. __exitcall(fn), functions which are labeled as exit calls.
> - *
> - * In addition, the variables defined using DEFINE_PERCPU_FIRST are
> - * also not included, which currently includes:
> - *
> - * 1. fixed_percpu_data
> - */
> - if (!addr)
> - continue;
> + sym_name = elf_sym__name(sym, btfe->symtab);
> + if (!btf_name_valid(sym_name)) {
> + dump_invalid_symbol("Found symbol of invalid name when encoding btf",
> + sym_name, btf_elf__verbose, btf_elf__force);
> + if (btf_elf__force)
> + return 0;
> + return -1;
> + }
>
> - size = elf_sym__size(&sym);
> - if (!size)
> - continue; /* ignore zero-sized symbols */
> + if (btf_elf__verbose)
> + printf("Found per-CPU symbol '%s' at address 0x%lx\n", sym_name, addr);
>
> - sym_name = elf_sym__name(&sym, btfe->symtab);
> - if (!btf_name_valid(sym_name)) {
> - dump_invalid_symbol("Found symbol of invalid name when encoding btf",
> - sym_name, btf_elf__verbose, btf_elf__force);
> - if (btf_elf__force)
> - continue;
> - return -1;
> - }
> + if (percpu_var_cnt == MAX_PERCPU_VAR_CNT) {
> + fprintf(stderr, "Reached the limit of per-CPU variables: %d\n",
> + MAX_PERCPU_VAR_CNT);
> + return -1;
> + }
> + percpu_vars[percpu_var_cnt].addr = addr;
> + percpu_vars[percpu_var_cnt].sz = size;
> + percpu_vars[percpu_var_cnt].name = sym_name;
> + percpu_var_cnt++;
>
> - if (btf_elf__verbose)
> - printf("Found per-CPU symbol '%s' at address 0x%lx\n", sym_name, addr);
> + return 0;
> +}
> +
> +static int collect_symbols(struct btf_elf *btfe, bool collect_percpu_vars)
> +{
> + uint32_t core_id;
> + GElf_Sym sym;
>
> - if (percpu_var_cnt == MAX_PERCPU_VAR_CNT) {
> - fprintf(stderr, "Reached the limit of per-CPU variables: %d\n",
> - MAX_PERCPU_VAR_CNT);
> + /* cache variables' addresses, preparing for searching in symtab. */
> + percpu_var_cnt = 0;
> +
> + /* search within symtab for percpu variables */
> + elf_symtab__for_each_symbol(btfe->symtab, core_id, sym) {
> + if (collect_percpu_vars && collect_percpu_var(btfe, &sym))
> return -1;
> - }
> - percpu_vars[percpu_var_cnt].addr = addr;
> - percpu_vars[percpu_var_cnt].sz = size;
> - percpu_vars[percpu_var_cnt].name = sym_name;
> - percpu_var_cnt++;
> }
>
> - if (percpu_var_cnt)
> - qsort(percpu_vars, percpu_var_cnt, sizeof(percpu_vars[0]), percpu_var_cmp);
> + if (collect_percpu_vars) {
> + if (percpu_var_cnt)
> + qsort(percpu_vars, percpu_var_cnt, sizeof(percpu_vars[0]), percpu_var_cmp);
>
> - if (btf_elf__verbose)
> - printf("Found %d per-CPU variables!\n", percpu_var_cnt);
> + if (btf_elf__verbose)
> + printf("Found %d per-CPU variables!\n", percpu_var_cnt);
> + }
> return 0;
> }
>
> @@ -347,7 +357,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
> if (!btfe)
> return -1;
>
> - if (!skip_encoding_vars && find_all_percpu_vars(btfe))
> + if (collect_symbols(btfe, !skip_encoding_vars))
> goto out;
>
> has_index_type = false;
> --
> 2.26.2
>
