| Message ID | 20230521160426.1881124-6-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Unify <linux/export.h> and <asm/export.h>, remove EXPORT_DATA_SYMBOL(), faster TRIM_UNUSED_KSYMS | expand |
On Sun, May 21, 2023 at 9:05 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > find_fromsym() and find_tosym() are similar - both of them iterate > in the .symtab section and return the nearest symbol. > > The difference between them is that find_tosym() allows a negative > distance, but the distance must be less than 20. > > Factor out the common part into find_nearest_sym(). > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Thanks for the patch! Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > --- > > Changes in v6: > - Revive the check for distance less than 20 > > scripts/mod/modpost.c | 95 ++++++++++++++++--------------------------- > 1 file changed, 36 insertions(+), 59 deletions(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index d2329ac32177..6ac0d571542c 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -1104,81 +1104,58 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym) > return !is_mapping_symbol(name); > } > > -/** > - * Find symbol based on relocation record info. > - * In some cases the symbol supplied is a valid symbol so > - * return refsym. If is_valid_name() == true, we assume this is a valid symbol. > - * In other cases the symbol needs to be looked up in the symbol table > - * based on section and address. > - * **/ > -static Elf_Sym *find_tosym(struct elf_info *elf, Elf64_Sword addr, > - Elf_Sym *relsym) > +/* Look up the nearest symbol based on the section and the address */ > +static Elf_Sym *find_nearest_sym(struct elf_info *elf, Elf_Addr addr, > + unsigned int secndx, bool allow_negative, > + Elf_Addr min_distance) > { > Elf_Sym *sym; > Elf_Sym *near = NULL; > - Elf64_Sword distance = 20; > - Elf64_Sword d; > - unsigned int relsym_secindex; > - > - if (is_valid_name(elf, relsym)) > - return relsym; > - > - /* > - * Strive to find a better symbol name, but the resulting name does not > - * always match the symbol referenced in the original code. > - */ > - relsym_secindex = get_secindex(elf, relsym); > - for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) { > - if (get_secindex(elf, sym) != relsym_secindex) > - continue; > - if (ELF_ST_TYPE(sym->st_info) == STT_SECTION) > - continue; > - if (!is_valid_name(elf, sym)) > - continue; > - if (sym->st_value == addr) > - return sym; > - /* Find a symbol nearby - addr are maybe negative */ > - d = sym->st_value - addr; > - if (d < 0) > - d = addr - sym->st_value; > - if (d < distance) { > - distance = d; > - near = sym; > - } > - } > - /* We need a close match */ > - if (distance < 20) > - return near; > - else > - return NULL; > -} > - > -/* > - * Find symbols before or equal addr and after addr - in the section sec. > - * If we find two symbols with equal offset prefer one with a valid name. > - * The ELF format may have a better way to detect what type of symbol > - * it is, but this works for now. > - **/ > -static Elf_Sym *find_fromsym(struct elf_info *elf, Elf_Addr addr, > - unsigned int secndx) > -{ > - Elf_Sym *sym; > - Elf_Sym *near = NULL; > - Elf_Addr distance = ~0; > + Elf_Addr distance; > > for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) { > if (get_secindex(elf, sym) != secndx) > continue; > if (!is_valid_name(elf, sym)) > continue; > - if (sym->st_value <= addr && addr - sym->st_value <= distance) { > + > + if (addr >= sym->st_value) > distance = addr - sym->st_value; > + else if (allow_negative) > + distance = sym->st_value - addr; > + else > + continue; > + > + if (distance <= min_distance) { > + min_distance = distance; > near = sym; > } > + > + if (min_distance == 0) > + break; > } > return near; > } > > +static Elf_Sym *find_fromsym(struct elf_info *elf, Elf_Addr addr, > + unsigned int secndx) > +{ > + return find_nearest_sym(elf, addr, secndx, false, ~0); > +} > + > +static Elf_Sym *find_tosym(struct elf_info *elf, Elf_Addr addr, Elf_Sym *sym) > +{ > + /* If the supplied symbol has a valid name, return it */ > + if (is_valid_name(elf, sym)) > + return sym; > + > + /* > + * Strive to find a better symbol name, but the resulting name does not > + * always match the symbol referenced in the original code. > + */ > + return find_nearest_sym(elf, addr, get_secindex(elf, sym), true, 20); > +} > + > static bool is_executable_section(struct elf_info *elf, unsigned int secndx) > { > if (secndx > elf->num_sections) > -- > 2.39.2 >
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index d2329ac32177..6ac0d571542c 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1104,81 +1104,58 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym) return !is_mapping_symbol(name); } -/** - * Find symbol based on relocation record info. - * In some cases the symbol supplied is a valid symbol so - * return refsym. If is_valid_name() == true, we assume this is a valid symbol. - * In other cases the symbol needs to be looked up in the symbol table - * based on section and address. - * **/ -static Elf_Sym *find_tosym(struct elf_info *elf, Elf64_Sword addr, - Elf_Sym *relsym) +/* Look up the nearest symbol based on the section and the address */ +static Elf_Sym *find_nearest_sym(struct elf_info *elf, Elf_Addr addr, + unsigned int secndx, bool allow_negative, + Elf_Addr min_distance) { Elf_Sym *sym; Elf_Sym *near = NULL; - Elf64_Sword distance = 20; - Elf64_Sword d; - unsigned int relsym_secindex; - - if (is_valid_name(elf, relsym)) - return relsym; - - /* - * Strive to find a better symbol name, but the resulting name does not - * always match the symbol referenced in the original code. - */ - relsym_secindex = get_secindex(elf, relsym); - for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) { - if (get_secindex(elf, sym) != relsym_secindex) - continue; - if (ELF_ST_TYPE(sym->st_info) == STT_SECTION) - continue; - if (!is_valid_name(elf, sym)) - continue; - if (sym->st_value == addr) - return sym; - /* Find a symbol nearby - addr are maybe negative */ - d = sym->st_value - addr; - if (d < 0) - d = addr - sym->st_value; - if (d < distance) { - distance = d; - near = sym; - } - } - /* We need a close match */ - if (distance < 20) - return near; - else - return NULL; -} - -/* - * Find symbols before or equal addr and after addr - in the section sec. - * If we find two symbols with equal offset prefer one with a valid name. - * The ELF format may have a better way to detect what type of symbol - * it is, but this works for now. - **/ -static Elf_Sym *find_fromsym(struct elf_info *elf, Elf_Addr addr, - unsigned int secndx) -{ - Elf_Sym *sym; - Elf_Sym *near = NULL; - Elf_Addr distance = ~0; + Elf_Addr distance; for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) { if (get_secindex(elf, sym) != secndx) continue; if (!is_valid_name(elf, sym)) continue; - if (sym->st_value <= addr && addr - sym->st_value <= distance) { + + if (addr >= sym->st_value) distance = addr - sym->st_value; + else if (allow_negative) + distance = sym->st_value - addr; + else + continue; + + if (distance <= min_distance) { + min_distance = distance; near = sym; } + + if (min_distance == 0) + break; } return near; } +static Elf_Sym *find_fromsym(struct elf_info *elf, Elf_Addr addr, + unsigned int secndx) +{ + return find_nearest_sym(elf, addr, secndx, false, ~0); +} + +static Elf_Sym *find_tosym(struct elf_info *elf, Elf_Addr addr, Elf_Sym *sym) +{ + /* If the supplied symbol has a valid name, return it */ + if (is_valid_name(elf, sym)) + return sym; + + /* + * Strive to find a better symbol name, but the resulting name does not + * always match the symbol referenced in the original code. + */ + return find_nearest_sym(elf, addr, get_secindex(elf, sym), true, 20); +} + static bool is_executable_section(struct elf_info *elf, unsigned int secndx) { if (secndx > elf->num_sections)
find_fromsym() and find_tosym() are similar - both of them iterate in the .symtab section and return the nearest symbol. The difference between them is that find_tosym() allows a negative distance, but the distance must be less than 20. Factor out the common part into find_nearest_sym(). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Changes in v6: - Revive the check for distance less than 20 scripts/mod/modpost.c | 95 ++++++++++++++++--------------------------- 1 file changed, 36 insertions(+), 59 deletions(-)