elf.5: Fix description of STV_PROTECTED

Quoting Mike:

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.

Reported-by: Gabriel Corona <gabriel.corona@enst-bretagne.fr>
Reported-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

This commit is contained in:

Michael Kerrisk

2016-03-09 19:25:22 +01:00

parent db337e545c

commit 2c8e09b4ff

1 changed files with 2 additions and 1 deletions

									
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man5/elf.5

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				@ -1553,7 +1553,8 @@ Processor-specific hidden class

				Symbol is unavailable in other modules

				.TP

				.BR STV_PROTECTED

				Not preemptible, not exported

				Symbol is available in other modules,

				but references in the local module always resolve to the local symbol.

				.PD

				.PP

				There are macros for extracting the visibility type:

elf.5: Fix description of STV_PROTECTED

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