Make the directory mapping functionality, which was previously only
available in 32-bit compatibility mode, unconditional. Overhaul the man page, which had evolved more by accretion than by design. Approved by: re (gjb) MFC after: 3 weeks
This commit is contained in:
Dag-Erling Smørgrav
parent
ad5b574375
commit
8182b3bee1
@ -396,7 +396,6 @@ lm_find (const char *p, const char *f)
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/* Given a libmap translation list and a library name, return the
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replacement library, or NULL */
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#ifdef COMPAT_32BIT
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char *
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lm_findn (const char *p, const char *f, const int n)
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{
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@ -413,7 +412,6 @@ lm_findn (const char *p, const char *f, const int n)
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free(s);
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return (t);
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}
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#endif
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static char *
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lml_find (struct lm_list *lmh, const char *f)
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@ -5,6 +5,4 @@
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int lm_init (char *);
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void lm_fini (void);
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char * lm_find (const char *, const char *);
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#ifdef COMPAT_32BIT
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char * lm_findn (const char *, const char *, const int);
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#endif
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@ -2581,12 +2581,14 @@ rtld_exit(void)
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lock_release(rtld_bind_lock, &lockstate);
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}
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/*
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* Iterate over a search path, translate each element, and invoke the
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* callback on the result.
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*/
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static void *
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path_enumerate(const char *path, path_enum_proc callback, void *arg)
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{
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#ifdef COMPAT_32BIT
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const char *trans;
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#endif
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if (path == NULL)
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return (NULL);
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@ -2596,13 +2598,11 @@ path_enumerate(const char *path, path_enum_proc callback, void *arg)
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char *res;
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len = strcspn(path, ":;");
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#ifdef COMPAT_32BIT
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trans = lm_findn(NULL, path, len);
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if (trans)
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res = callback(trans, strlen(trans), arg);
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else
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#endif
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res = callback(path, len, arg);
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res = callback(path, len, arg);
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if (res != NULL)
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return (res);
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@ -1,4 +1,5 @@
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.\" Copyright (c) 2003 Matthew N. Dodd <winter@jurai.net>
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.\" Copyright (c) 2013 Dag-Erling Smørgrav
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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@ -24,7 +25,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 28, 2012
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.Dd September 16, 2013
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.Dt LIBMAP.CONF 5
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.Os
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.Sh NAME
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@ -35,109 +36,105 @@ The
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.Nm libmap
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functionality of
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.Xr ld-elf.so.1 1
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allows dynamic object dependencies to be mapped to arbitrary
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names.
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allows dynamic object dependencies to be mapped to arbitrary names.
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.Pp
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The configuration file consists of two whitespace separated columns; the
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left hand side containing the mapping candidate and the right hand
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side containing the mapping.
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Dependencies are matched against candidates and replaced with the mappings.
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.Pp
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Two special directives are available:
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Each line in
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.Pa /etc/libmap.conf
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can have one of five forms:
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.Bl -tag -width indent
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.It Ar origin Ar target
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Whenever a dependency on
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.Ar origin
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is encountered while loading a dynamic object, use
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.Ar target
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instead of searching for
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.Ar origin
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in the normal library search paths.
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.It Ar path1 Ar path2
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When iterating through a library search path, replace any element that
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matches
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.Ar path1
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exactly with
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.Ar path2 .
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.It Bq Ar constraint
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Apply
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.Ar constraint
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to all subsequent mappings until the next constraint line or the end
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of the file.
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See the
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.Sx Constraints
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section for details.
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.It Cm include Ar file
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Parse the contents of
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.Ar file
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before continuing with the current file.
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Nesting depth is limited only by available memory, but each file
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encountered is processed only once, and loops are silently ignored.
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.It Cm includedir Ar dir
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Parse the contents of every file in
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Recurse through
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.Ar dir
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that ends in
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and parse the contents of any file that ends in
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.Pa .conf
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before continuing with the current file.
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Nesting depth is limited only by available memory, but each directory
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or file encountered is processed only once, and loops are silently
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ignored.
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.El
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.Pp
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Any file or directory encountered while processing
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.Cm include
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or
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.Cm includedir
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directives will be parsed exactly once, even if it is encountered
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multiple times.
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.Pp
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Constrained mappings may be specified by enclosing the name of the
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executable or library in brackets.
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All mappings following a constraint will only be evaluated for that constraint.
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Constraints can be one of three types:
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.Ss Constraints
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Constrained mappings only apply when processing binaries or libraries
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that satisfy the constraint.
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There are three types of constraints:
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.Bl -tag -width indent
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.It Exact
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The constraint is matched literally so that only an executable with an
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identical fully qualified pathname will match the constraint.
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identical fully qualified pathname will satisfy the constraint.
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This means that the executable
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.Pa /usr/bin/foo
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will not match a constraint for
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.Pa /usr/bin/./foo
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will not satisfy the constraint
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.Bq Pa /usr/bin/./foo ,
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and vice-versa.
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This is the default constraint type.
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.It Basename
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A constraint with no path is matched against the basename of the
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executable.
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.Pa foo
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For instance, the constraint
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.Bq Pa foo
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will match
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.Pa /bin/foo ,
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.Pa /usr/local/sbin/foo ,
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or any other executable named
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.Pa foo ,
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no matter what its path is.
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no matter what directory it is in.
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.It Directory
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A constraint with a trailing slash is prefix-matched against the full
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pathname of the executable.
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.Pa /usr/bin/
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will match any executable with a path starting with /usr/bin.
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A constraint with a trailing slash is satisfied if the full pathname
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begins with the constraint string.
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For instance, the constraint
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.Bq Pa /usr/bin/
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will match any executable with a path starting with
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.Pa /usr/bin/ .
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.El
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.Pp
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Note that the executable path matched against is the
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.Fa path
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parameter in an
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.Fn exec*
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function call.
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The Directory or Exact constraints can only match when the executable
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is called with a full pathname.
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Note that the constraints are matched against the path that was passed
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as the first argument to whichever
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.Xr exec 3
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function was used to execute the binary in question.
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Most programs executed from a shell are run without a full path, via
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.Fn exec*p ,
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so the Basename constraint type is the most useful.
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.Xr execvp 3
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or similar, so the basename constraint type is the most useful.
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.Pp
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.Bf -symbolic
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WARNING!
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Constrained mappings must never appear first in the configuration file.
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While there is a way to specify the
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.Dq default
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constraint, its use is not recommended.
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.Pp
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The most common use at the date of writing is for allowing multiple
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.Tn POSIX
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threading libraries to be used on a system without relinking or
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changing symlinks.
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.Pp
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On 64-bit architectures that provide 32-bit runtime support,
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the libmap mechanism is available for 32-bit binaries too.
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The mappings has to be written into separate configuration file
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Constraints apply to all mappings until the next constraint or the end
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of the file.
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Hence, unconstrained mappings must be placed at the top of the file.
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.Ef
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.Ss ABI compatibility
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On 64-bit architectures that provide 32-bit binary compatibility, the
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mappings in
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.Pa /etc/libmap.conf
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apply only to 64-bit binaries.
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Mappings for 32-bit binaries must be placed in
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.Pa /etc/libmap32.conf .
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Currently only supported on amd64.
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.Pp
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This mechanism has also been used to create shims to allow Linux
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shared libraries to be dynamically loaded into
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.Fx
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binaries.
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In this case, an Exact constraint is used for the Linux shared library,
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mapping libraries it depends on to a wrapper.
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The wrapper then defines any needed symbols for the Linux shared library
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and relies on its libraries not being mapped to provide actual
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implementations.
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It appears that only libraries loaded via
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.Xr dlopen 3
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will work correctly.
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The symbol version information in shared libraries is checked at
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link time, but at run time the version information is currently
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ignored.
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.Sh FILES
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.Bl -tag -width ".Pa /etc/libmap32.conf" -compact
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.It Pa /etc/libmap.conf
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@ -147,9 +144,8 @@ The libmap configuration file for 32-bit binaries on 64-bit system.
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.El
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.Sh EXAMPLES
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.Bd -literal
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# /etc/libmap.conf
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#
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# candidate mapping
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# origin target
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#
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libc_r.so.6 libpthread.so.2 # Everything that uses 'libc_r'
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libc_r.so libpthread.so # now uses 'libpthread'
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@ -174,11 +170,11 @@ libdl.so.2 pluginwrapper/pips.so
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.Xr rtld 1
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.Sh HISTORY
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The
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.Nm
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manual page and
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.Nm libmap
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functionality first appeared in
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mechanism first appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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This manual page was written by
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.An Matthew N. Dodd Aq winter@jurai.net .
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.An Matthew N. Dodd Aq winter@jurai.net
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and extensively rewritten by
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.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
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