Hi Mike, On 9 March 2016 at 06:01, Mike Frysinger <vapier@xxxxxxxxxx> wrote: > 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." ? Thanks for the detailed confirmation, Mike. I made the text: STV_PROTECTED Symbol is available in other modules, but references in the local module always resolve to the local symbol. Thanks for the report Gabriel! Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
