Use a CFI cache's corresponding dwfl load_lock to serialize its initialization. Rename __libdwfl_set_cfi to __libdwfl_set_cfi_locked to indicate that the caller must hold the load_lock. Atomics are used to acquire an initialized CFI cache without needing to obtain the load_lock.
Signed-off-by: Aaron Merey <[email protected]> --- v2 changes: in __libdwfl_set_cfi_locked, return early if slot isn't either &mod->eh_cfi or &mod->dwarf_cfi. Also acquire cfi->lock before setting cfi->ebl. libdwfl/dwfl_module.c | 2 +- libdwfl/dwfl_module_dwarf_cfi.c | 38 ++++++++++++++++++++++++++------- libdwfl/dwfl_module_eh_cfi.c | 26 +++++++++++++++------- libdwfl/libdwflP.h | 7 +++--- 4 files changed, 53 insertions(+), 20 deletions(-) diff --git a/libdwfl/dwfl_module.c b/libdwfl/dwfl_module.c index b4ddf806..27e6c064 100644 --- a/libdwfl/dwfl_module.c +++ b/libdwfl/dwfl_module.c @@ -74,7 +74,7 @@ __libdwfl_module_free (Dwfl_Module *mod) } /* We might have primed the Dwarf_CFI ebl cache with our own ebl - in __libdwfl_set_cfi. Make sure we don't free it twice. */ + in __libdwfl_set_cfi_locked. Make sure we don't free it twice. */ if (mod->eh_cfi != NULL) { if (mod->eh_cfi->ebl != NULL && mod->eh_cfi->ebl == mod->ebl) diff --git a/libdwfl/dwfl_module_dwarf_cfi.c b/libdwfl/dwfl_module_dwarf_cfi.c index 05a14f7c..a8b2d9a5 100644 --- a/libdwfl/dwfl_module_dwarf_cfi.c +++ b/libdwfl/dwfl_module_dwarf_cfi.c @@ -35,15 +35,26 @@ Dwarf_CFI * internal_function -__libdwfl_set_cfi (Dwfl_Module *mod, Dwarf_CFI **slot, Dwarf_CFI *cfi) +__libdwfl_set_cfi_locked (Dwfl_Module *mod, Dwarf_CFI **slot, Dwarf_CFI *cfi) { - if (cfi != NULL && cfi->ebl == NULL) + if (slot != &mod->eh_cfi && slot != &mod->dwarf_cfi) + { + __libdwfl_seterrno (DWFL_E_INVALID_ARGUMENT); + return NULL; + } + + if (cfi == NULL) + return NULL; + + mutex_lock (cfi->lock); + if (cfi->ebl == NULL) { Dwfl_Error error = __libdwfl_module_getebl (mod); if (error == DWFL_E_NOERROR) cfi->ebl = mod->ebl; else { + mutex_unlock (cfi->lock); if (slot == &mod->eh_cfi) INTUSE(dwarf_cfi_end) (cfi); __libdwfl_seterrno (error); @@ -51,7 +62,9 @@ __libdwfl_set_cfi (Dwfl_Module *mod, Dwarf_CFI **slot, Dwarf_CFI *cfi) } } - return *slot = cfi; + atomic_store_release (slot, cfi); + mutex_unlock (cfi->lock); + return cfi; } Dwarf_CFI * @@ -60,14 +73,23 @@ dwfl_module_dwarf_cfi (Dwfl_Module *mod, Dwarf_Addr *bias) if (mod == NULL) return NULL; - if (mod->dwarf_cfi != NULL) + Dwarf_CFI *cfi = atomic_load_acquire (&mod->dwarf_cfi); + if (cfi != NULL) { *bias = dwfl_adjusted_dwarf_addr (mod, 0); - return mod->dwarf_cfi; + return cfi; } - return __libdwfl_set_cfi (mod, &mod->dwarf_cfi, - INTUSE(dwarf_getcfi) - (INTUSE(dwfl_module_getdwarf) (mod, bias))); + mutex_lock (mod->dwfl->load_lock); + cfi = mod->dwarf_cfi; + if (cfi == NULL) + cfi = __libdwfl_set_cfi_locked (mod, &mod->dwarf_cfi, + INTUSE(dwarf_getcfi) + (INTUSE(dwfl_module_getdwarf) (mod, bias))); + else + *bias = dwfl_adjusted_dwarf_addr (mod, 0); + + mutex_unlock (mod->dwfl->load_lock); + return cfi; } INTDEF (dwfl_module_dwarf_cfi) diff --git a/libdwfl/dwfl_module_eh_cfi.c b/libdwfl/dwfl_module_eh_cfi.c index aac6657d..cc28ad60 100644 --- a/libdwfl/dwfl_module_eh_cfi.c +++ b/libdwfl/dwfl_module_eh_cfi.c @@ -39,21 +39,31 @@ dwfl_module_eh_cfi (Dwfl_Module *mod, Dwarf_Addr *bias) if (mod == NULL) return NULL; - if (mod->eh_cfi != NULL) + Dwarf_CFI *cfi = atomic_load_acquire (&mod->eh_cfi); + if (cfi != NULL) { *bias = dwfl_adjusted_address (mod, 0); - return mod->eh_cfi; + return cfi; } - __libdwfl_getelf (mod); - if (mod->elferr != DWFL_E_NOERROR) + mutex_lock (mod->dwfl->load_lock); + cfi = mod->eh_cfi; + if (cfi == NULL) { - __libdwfl_seterrno (mod->elferr); - return NULL; + __libdwfl_getelf (mod); + if (mod->elferr != DWFL_E_NOERROR) + { + __libdwfl_seterrno (mod->elferr); + mutex_unlock (mod->dwfl->load_lock); + return NULL; + } + + cfi = __libdwfl_set_cfi_locked (mod, &mod->eh_cfi, + INTUSE(dwarf_getcfi_elf) (mod->main.elf)); } + mutex_unlock (mod->dwfl->load_lock); *bias = dwfl_adjusted_address (mod, 0); - return __libdwfl_set_cfi (mod, &mod->eh_cfi, - INTUSE(dwarf_getcfi_elf) (mod->main.elf)); + return cfi; } INTDEF (dwfl_module_eh_cfi) diff --git a/libdwfl/libdwflP.h b/libdwfl/libdwflP.h index 6e2c2f8b..3b4df7e8 100644 --- a/libdwfl/libdwflP.h +++ b/libdwfl/libdwflP.h @@ -529,9 +529,10 @@ extern Dwfl_Error __libdwfl_relocate_value (Dwfl_Module *mod, Elf *elf, /* Ensure that MOD->ebl is set up. */ extern Dwfl_Error __libdwfl_module_getebl (Dwfl_Module *mod) internal_function; -/* Install a new Dwarf_CFI in *SLOT (MOD->eh_cfi or MOD->dwarf_cfi). */ -extern Dwarf_CFI *__libdwfl_set_cfi (Dwfl_Module *mod, Dwarf_CFI **slot, - Dwarf_CFI *cfi) +/* Install a new Dwarf_CFI in *SLOT (MOD->eh_cfi or MOD->dwarf_cfi). + MOD->dwfl->load_lock must be held by the caller. */ +extern Dwarf_CFI *__libdwfl_set_cfi_locked (Dwfl_Module *mod, Dwarf_CFI **slot, + Dwarf_CFI *cfi) internal_function; /* Iterate through all the CU's in the module. Start by passing a null -- 2.56.0
