From: Mark Wielaard Date: Sun, 15 Jun 2014 11:30:35 +0200 Subject: libebl: Add sym_func_value hook. The ARM EABI says that the zero bit of function symbol st_value indicates whether the symbol points to a THUMB or ARM function. Add a new ebl hook to adjust the st_value in such a case so that we get the actual value that the symbol points to. It isn't easily possible to reuse the existing resolve_sym_value for this purpose, so we end up with another hook that can be used from dwfl_module_getsym and elflint. Rebase arm_func_value.patch from 0.159 to 0.160 Signed-off-by: Hongxu Jia --- backends/arm_init.c | 1 + backends/arm_symbol.c | 8 ++++++++ libdwfl/dwfl_module_getsym.c | 2 +- libebl/Makefile.am | 3 ++- libebl/ebl-hooks.h | 3 +++ libebl/eblsymfuncval.c | 43 ++++++++++++++++++++++++++++++++++++++++++ libebl/libebl.h | 11 +++++++++++ 7 files changed, 69 insertions(+), 2 deletions(-) diff --git a/backends/arm_init.c b/backends/arm_init.c index 7171186..9f03630 100644 --- a/backends/arm_init.c +++ b/backends/arm_init.c @@ -78,6 +78,7 @@ arm_init (elf, machine, eh, ehlen) eh->return_value_location = arm_return_value_location_hard; HOOK (eh, abi_cfi); HOOK (eh, check_reloc_target_type); + HOOK (eh, sym_func_value); HOOK (eh, symbol_type_name); /* We only unwind the core integer registers. */ diff --git a/backends/arm_symbol.c b/backends/arm_symbol.c index da4a50a..ccea03b 100644 --- a/backends/arm_symbol.c +++ b/backends/arm_symbol.c @@ -130,6 +130,14 @@ arm_check_reloc_target_type (Ebl *ebl __attribute__ ((unused)), Elf64_Word sh_ty return sh_type == SHT_ARM_EXIDX; } +/* ARM EABI says that the low bit indicates whether the function + symbol value is a THUMB function or not. Mask it off. */ +GElf_Addr +arm_sym_func_value (Ebl *ebl __attribute__ ((unused)), GElf_Addr val) +{ + return val & ~(GElf_Addr)1; +} + const char * arm_symbol_type_name (int type, char *buf __attribute__ ((unused)), diff --git a/libdwfl/dwfl_module_getsym.c b/libdwfl/dwfl_module_getsym.c index 42d2b67..fb192d7 100644 --- a/libdwfl/dwfl_module_getsym.c +++ b/libdwfl/dwfl_module_getsym.c @@ -119,7 +119,7 @@ __libdwfl_getsym (Dwfl_Module *mod, int ndx, GElf_Sym *sym, GElf_Addr *addr, descriptors). */ char *ident; - GElf_Addr st_value = sym->st_value & ebl_func_addr_mask (mod->ebl); + GElf_Addr st_value = ebl_sym_func_value (mod->ebl, sym->st_value); *resolved = false; if (! adjust_st_value && mod->e_type != ET_REL && alloc && (GELF_ST_TYPE (sym->st_info) == STT_FUNC diff --git a/libebl/Makefile.am b/libebl/Makefile.am index ec4477b..889c21b 100644 --- a/libebl/Makefile.am +++ b/libebl/Makefile.am @@ -55,7 +55,8 @@ gen_SOURCES = eblopenbackend.c eblclosebackend.c eblstrtab.c \ eblsysvhashentrysize.c eblauxvinfo.c eblcheckobjattr.c \ ebl_check_special_section.c ebl_syscall_abi.c eblabicfi.c \ eblstother.c eblinitreg.c ebldwarftoregno.c eblnormalizepc.c \ - eblunwind.c eblresolvesym.c eblcheckreloctargettype.c + eblunwind.c eblresolvesym.c eblcheckreloctargettype.c \ + eblsymfuncval.c libebl_a_SOURCES = $(gen_SOURCES) diff --git a/libebl/ebl-hooks.h b/libebl/ebl-hooks.h index 2e31446..9df945d 100644 --- a/libebl/ebl-hooks.h +++ b/libebl/ebl-hooks.h @@ -191,5 +191,8 @@ bool EBLHOOK(unwind) (Ebl *ebl, Dwarf_Addr pc, ebl_tid_registers_t *setfunc, (e.g. function descriptor resolving) */ bool EBLHOOK(resolve_sym_value) (Ebl *ebl, GElf_Addr *addr); +/* Returns the real value of a symbol function address or offset. */ +GElf_Addr EBLHOOK(sym_func_value) (Ebl *ebl, GElf_Addr val); + /* Destructor for ELF backend handle. */ void EBLHOOK(destr) (struct ebl *); diff --git a/libebl/eblsymfuncval.c b/libebl/eblsymfuncval.c new file mode 100644 index 0000000..c0b322f --- /dev/null +++ b/libebl/eblsymfuncval.c @@ -0,0 +1,43 @@ +/* Turn a symbol function value into a real function address or offset. + Copyright (C) 2014 Red Hat, Inc. + This file is part of elfutils. + + This file is free software; you can redistribute it and/or modify + it under the terms of either + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at + your option) any later version + + or + + * the GNU General Public License as published by the Free + Software Foundation; either version 2 of the License, or (at + your option) any later version + + or both in parallel, as here. + + elfutils is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received copies of the GNU General Public License and + the GNU Lesser General Public License along with this program. If + not, see . */ + +#ifdef HAVE_CONFIG_H +# include +#endif + +#include +#include + +GElf_Addr +ebl_sym_func_value (Ebl *ebl, GElf_Addr val) +{ + if (ebl == NULL || ebl->sym_func_value == NULL) + return val; + + return ebl->sym_func_value (ebl, val); +} diff --git a/libebl/libebl.h b/libebl/libebl.h index 7dbf460..96c076b 100644 --- a/libebl/libebl.h +++ b/libebl/libebl.h @@ -472,6 +472,17 @@ extern bool ebl_unwind (Ebl *ebl, Dwarf_Addr pc, ebl_tid_registers_t *setfunc, extern bool ebl_resolve_sym_value (Ebl *ebl, GElf_Addr *addr) __nonnull_attribute__ (2); +/* Returns the real value of a symbol function address or offset + (e.g. when the st_value contains some flag bits that need to be + masked off). This is different from ebl_resolve_sym_value which + only works for actual symbol addresses (in non-ET_REL files) that + might resolve to an address in a different section. + ebl_sym_func_value is called to turn the given value into the a + real address or offset (the original value might not be a real + address). This works for both ET_REL when the value is a section + offset or ET_EXEC or ET_DYN symbol values, which are addresses. */ +extern GElf_Addr ebl_sym_func_value (Ebl *ebl, GElf_Addr val); + #ifdef __cplusplus } #endif