On 09 Mar 2016 02:03, Michael Kerrisk (man-pages) wrote: > On 09/29/2015 12:14 PM, Gabriel Corona wrote: > > The elf manpage [2] claims that: > > > >> STV_PROTECTED Not preemptible, not exported. > > > > However the System V gABI [1] claims that: > > > >> A symbol defined in the current component is protected if it is > >> visible in other components but not preemptable > > > > Should the manpage read something like: > > > >> STV_PROTECTED Not preemptible but exported. > > > > [1] http://www.sco.com/developers/gabi/2003-12-17/ch4.symtab.html > > > > [2] http://man7.org/linux/man-pages/man5/elf.5.html > > I think you are right, but let's see if Mike might confirm, > since he originally added that text. (Mike, I suspect there > was a wordo here.) i didn't really author that content, but take it from elf.h in glibc: #define STV_PROTECTED 3 /* Not preemptible, not exported */ and binutils says: #define STV_PROTECTED 3 /* Treat as STB_LOCAL inside current component */ and llvm says: STV_PROTECTED = 3 // Visible in other components but not preemptable gabi says: https://refspecs.linuxbase.org/elf/gabi4+/ch4.symtab.html A symbol defined in the current component is protected if it is visible in other components but not preemptable, meaning that any reference to such a symbol from within the defining component must be resolved to the definition in that component, even if there is a definition in another component that would preempt by the default rules. A symbol with STB_LOCAL binding may not have STV_PROTECTED visibility. If a symbol definition with STV_PROTECTED visibility from a shared object is taken as resolving a reference from an executable or another shared object, the SHN_UNDEF symbol table entry created has STV_DEFAULT visibility. solaris/oracle says: https://docs.oracle.com/cd/E26502_01/html/E26507/chapter6-79797.html A symbol that is defined in the current component is protected if the symbol is visible in other components, but cannot be preempted. Any reference to such a symbol from within the defining component must be resolved to the definition in that component. This resolution must occur, even if a symbol definition exists in another component that would interpose by the default rules. A symbol with STB_LOCAL binding will not have STV_PROTECTED visibility. but i think this ibm article is probably the most understandable: https://www.ibm.com/developerworks/aix/library/au-aix-symbol-visibility/ The symbol is visible outside the current executable or shared object, but it may not be overridden. In other words, if a protected symbol in a shared library is referenced by an other code in the shared library, the other code will always reference the symbol in the shared library, even if the executable defines a symbol with the same name. so while "Not preemptible but exported" is more correct, i'm not sure it's still all that great. maybe "Exported; not preemptible in current module." ? -mike
Attachment:
signature.asc
Description: Digital signature
