libvirt/tests/virmock.h
Daniel P. Berrangé ff376c6283 tests: fix mocking of stat() / lstat() functions
Quite a few of the tests have a need to mock the stat() / lstat()
functions and they are taking somewhat different & inconsistent
approaches none of which are actually fully correct. This is shown
by fact that 'make check' fails on 32-bit hosts. Investigation
revealed that the code was calling into the native C library impl,
not getting intercepted by our mocks.

The POSIX stat() function might resolve to any number of different
symbols in the C library.

The may be an additional stat64() function exposed by the headers
too.

On 64-bit hosts the stat & stat64 functions are identical, always
refering to the 64-bit ABI.

On 32-bit hosts they refer to the 32-bit & 64-bit ABIs respectively.

Libvirt uses _FILE_OFFSET_BITS=64 on 32-bit hosts, which causes the
C library to transparently rewrite stat() calls to be stat64() calls.
Libvirt will never see the 32-bit ABI from the traditional stat()
call. We cannot assume this rewriting is done using a macro. It might
be, but on GLibC it is done with a magic __asm__ statement to apply
the rewrite at link time instead of at preprocessing.

In GLibC there may be two additional functions exposed by the headers,
__xstat() and __xstat64(). When these exist, stat() and stat64() are
transparently rewritten to call __xstat() and __xstat64() respectively.
The former symbols will not actally exist in the library at all, only
the header. The leading "__" indicates the symbols are a private impl
detail of the C library that applications should not care about.
Unfortunately, because we are trying to mock replace the C library,
we need to know about this internal impl detail.

With all this in mind the list of functions we have to mock will depend
on several factors

 - If _FILE_OFFSET_BITS is set, then we are on a 32-bit host, and we
   only need to mock stat64 and __xstat64. The other stat / __xstat
   functions exist, but we'll never call them so they can be ignored
   for mocking.

 - If _FILE_OFFSET_BITS is not set, then we are on a 64-bit host and
   we should mock stat, stat64, __xstat & __xstat64. Either may be
   called by app code.

 - If __xstat & __xstat64 exist, then stat & stat64 will not exist
   as symbols in the library, so the latter should not be mocked.

The same all applies to lstat()

These rules are complex enough that we don't want to duplicate them
across every mock file, so this centralizes all the logic in a helper
file virmockstathelper.c that should be #included when needed. The
code merely need to provide a filename rewriting callback called
virMockStatRedirect(). Optionally VIR_MOCK_STAT_HOOK can be defined
as a macro if further processing is needed inline.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2019-04-03 11:31:38 +01:00

294 lines
11 KiB
C

/*
* virmock.h: helper for mocking C functions
*
* Copyright (C) 2014 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see
* <http://www.gnu.org/licenses/>.
*
*/
#ifndef LIBVIRT_VIRMOCK_H
# define LIBVIRT_VIRMOCK_H
# if HAVE_DLFCN_H
# include <dlfcn.h>
# endif
# include "internal.h"
# define VIR_MOCK_COUNT_ARGS(...) VIR_MOCK_ARG21(__VA_ARGS__, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1)
# define VIR_MOCK_ARG21(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, _21, ...) _21
# define VIR_MOCK_ARG_PASTE(a, b, ...) a##b(__VA_ARGS__)
# define VIR_MOCK_ARGNAME(a, b) b
# define VIR_MOCK_ARGTYPE(a, b) a
# define VIR_MOCK_ARGTYPENAME(a, b) a b
# define VIR_MOCK_ARGTYPENAME_UNUSED(a, b) a b ATTRIBUTE_UNUSED
# define VIR_MOCK_GET_ARG2(z, a, b) z(a, b)
# define VIR_MOCK_GET_ARG3(z, a, b, c) z(a, b)
# define VIR_MOCK_GET_ARG4(z, a, b, c, d) z(a, b), z(c, d)
# define VIR_MOCK_GET_ARG5(z, a, b, c, d, e) z(a, b), z(c, d)
# define VIR_MOCK_GET_ARG6(z, a, b, c, d, e, f) z(a, b), z(c, d), z(e, f)
# define VIR_MOCK_GET_ARG7(z, a, b, c, d, e, f, g) z(a, b), z(c, d), z(e, f)
# define VIR_MOCK_GET_ARG8(z, a, b, c, d, e, f, g, h) z(a, b), z(c, d), z(e, f), z(g, h)
# define VIR_MOCK_GET_ARG9(z, a, b, c, d, e, f, g, h, i) z(a, b), z(c, d), z(e, f), z(g, h)
# define VIR_MOCK_GET_ARG10(z, a, b, c, d, e, f, g, h, i, j) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j)
# define VIR_MOCK_GET_ARG11(z, a, b, c, d, e, f, g, h, i, j, k) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j)
# define VIR_MOCK_GET_ARG12(z, a, b, c, d, e, f, g, h, i, j, k, l) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l)
# define VIR_MOCK_GET_ARG13(z, a, b, c, d, e, f, g, h, i, j, k, l, m) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l)
# define VIR_MOCK_GET_ARG14(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n)
# define VIR_MOCK_GET_ARG15(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n)
# define VIR_MOCK_GET_ARG16(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n), z(o, p)
# define VIR_MOCK_GET_ARG17(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n), z(o, p)
# define VIR_MOCK_GET_ARG18(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n), z(o, p), z(q, r)
# define VIR_MOCK_GET_ARG19(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n), z(o, p), z(q, r)
# define VIR_MOCK_GET_ARG20(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n), z(o, p), z(q, r), z(s, t)
# define VIR_MOCK_GET_ARG21(z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u) z(a, b), z(c, d), z(e, f), z(g, h), z(i, j), z(k, l), z(m, n), z(o, p), z(q, r), z(s, t)
# define VIR_MOCK_ARGNAMES_EXPAND(a, b, ...) VIR_MOCK_ARG_PASTE(a, b, __VA_ARGS__)
# define VIR_MOCK_ARGNAMES(...) \
VIR_MOCK_ARGNAMES_EXPAND(VIR_MOCK_GET_ARG, VIR_MOCK_COUNT_ARGS(__VA_ARGS__), VIR_MOCK_ARGNAME, __VA_ARGS__)
# define VIR_MOCK_ARGTYPES_EXPAND(a, b, ...) VIR_MOCK_ARG_PASTE(a, b, __VA_ARGS__)
# define VIR_MOCK_ARGTYPES(...) \
VIR_MOCK_ARGTYPES_EXPAND(VIR_MOCK_GET_ARG, VIR_MOCK_COUNT_ARGS(__VA_ARGS__), VIR_MOCK_ARGTYPE, __VA_ARGS__)
# define VIR_MOCK_ARGTYPENAMES_EXPAND(a, b, ...) VIR_MOCK_ARG_PASTE(a, b, __VA_ARGS__)
# define VIR_MOCK_ARGTYPENAMES(...) \
VIR_MOCK_ARGTYPENAMES_EXPAND(VIR_MOCK_GET_ARG, VIR_MOCK_COUNT_ARGS(__VA_ARGS__), VIR_MOCK_ARGTYPENAME, __VA_ARGS__)
# define VIR_MOCK_ARGTYPENAMES_UNUSED_EXPAND(a, b, ...) VIR_MOCK_ARG_PASTE(a, b, __VA_ARGS__)
# define VIR_MOCK_ARGTYPENAMES_UNUSED(...) \
VIR_MOCK_ARGTYPENAMES_UNUSED_EXPAND(VIR_MOCK_GET_ARG, VIR_MOCK_COUNT_ARGS(__VA_ARGS__), VIR_MOCK_ARGTYPENAME_UNUSED, __VA_ARGS__)
/*
* The VIR_MOCK_LINK_NNN_MMM() macros are intended for use in
* LD_PRELOAD based wrappers. They provide a replacement for
* for an existing shared library symbol export. They will
* then lookup the same symbol name but with 'wrap_' prefixed
* on it, and call that.
*
* The actual test suite should provide the implementation of
* the wrap_XXXX symbol, using the VIR_MOCK_WRAP_NNN_MMM
* macros.
*/
/**
* VIR_MOCK_LINK_RET_ARGS:
* @name: the symbol name to replace
* @rettype: the return type
* @...: pairs of parameter type and parameter name
*
* Define a replacement for @name which invokes wrap_@name
* forwarding on all args, and passing back the return value.
*/
# define VIR_MOCK_LINK_RET_ARGS(name, rettype, ...) \
rettype name(VIR_MOCK_ARGTYPENAMES(__VA_ARGS__)) \
{ \
static rettype (*wrap_##name)(VIR_MOCK_ARGTYPES(__VA_ARGS__)); \
if (wrap_##name == NULL && \
!(wrap_##name = dlsym(RTLD_DEFAULT, \
"wrap_" #name))) { \
fprintf(stderr, "Missing symbol 'wrap_" #name "'\n"); \
abort(); \
} \
\
return wrap_##name(VIR_MOCK_ARGNAMES(__VA_ARGS__)); \
}
/**
* VIR_MOCK_LINK_RET_VOID:
* @name: the symbol name to replace
* @rettype: the return type
*
* Define a replacement for @name which invokes wrap_@name
* with no arguments, and passing back the return value.
*/
# define VIR_MOCK_LINK_RET_VOID(name, rettype) \
rettype name(void) \
{ \
static rettype (*wrap_##name)(void); \
if (wrap_##name == NULL && \
!(wrap_##name = dlsym(RTLD_DEFAULT, \
"wrap_" #name))) { \
fprintf(stderr, "Missing symbol 'wrap_" #name "'\n"); \
abort(); \
} \
\
return wrap_##name(); \
}
/**
* VIR_MOCK_LINK_VOID_ARGS:
* @name: the symbol name to replace
* @...: pairs of parameter type and parameter name
*
* Define a replacement for @name which invokes wrap_@name
* forwarding on all args, but with no return value.
*/
# define VIR_MOCK_LINK_VOID_ARGS(name, ...) \
void name(VIR_MOCK_ARGTYPENAMES(__VA_ARGS__)) \
{ \
static void (*wrap_##name)(VIR_MOCK_ARGTYPES(__VA_ARGS__)); \
if (wrap_##name == NULL && \
!(wrap_##name = dlsym(RTLD_DEFAULT, \
"wrap_" #name))) { \
fprintf(stderr, "Missing symbol 'wrap_" #name "'\n"); \
abort(); \
} \
\
wrap_##name(VIR_MOCK_ARGNAMES(__VA_ARGS__)); \
}
/*
* The VIR_MOCK_STUB_NNN_MMM() macros are intended for use in
* LD_PRELOAD based wrappers. They provide a replacement for
* for an existing shared library symbol export. They will
* be a pure no-op, optionally returning a dummy value.
*/
/**
* VIR_MOCK_STUB_RET_ARGS:
* @name: the symbol name to replace
* @rettype: the return type
* @retval: the return value
* @...: pairs of parameter type and parameter name
*
* Define a replacement for @name which doesn't invoke anything, just
* returns @retval.
*/
# define VIR_MOCK_STUB_RET_ARGS(name, rettype, retval, ...) \
rettype name(VIR_MOCK_ARGTYPENAMES_UNUSED(__VA_ARGS__)) \
{ \
return retval; \
}
/**
* VIR_MOCK_STUB_RET_VOID:
* @name: the symbol name to replace
* @rettype: the return type
* @retval: value to return
*
* Define a replacement for @name which doesn't invoke anything, just
* returns @retval.
*/
# define VIR_MOCK_STUB_RET_VOID(name, rettype, retval) \
rettype name(void) \
{ \
return retval; \
}
/**
* VIR_MOCK_STUB_VOID_ARGS:
* @name: the symbol name to replace
* @...: pairs of parameter type and parameter name
*
* Define a replacement for @name which doesn't invoke or return
* anything.
*/
# define VIR_MOCK_STUB_VOID_ARGS(name, ...) \
void name(VIR_MOCK_ARGTYPENAMES_UNUSED(__VA_ARGS__)) \
{ \
}
/**
* VIR_MOCK_STUB_VOID_VOID:
* @name: the symbol name to replace
*
* Define a replacement for @name which doesn't invoke or return
* anything.
*/
# define VIR_MOCK_STUB_VOID_VOID(name) \
void name(void) \
{ \
}
/*
* The VIR_MOCK_IMPL_NNN_MMM() macros are intended for use in the
* individual test suites. The define a stub implementation of
* the wrapped method and insert the caller provided code snippet
* as the body of the method.
*/
# define VIR_MOCK_IMPL_RET_ARGS(name, rettype, ...) \
rettype name(VIR_MOCK_ARGTYPENAMES(__VA_ARGS__)); \
static rettype (*real_##name)(VIR_MOCK_ARGTYPES(__VA_ARGS__)); \
rettype name(VIR_MOCK_ARGTYPENAMES_UNUSED(__VA_ARGS__))
# define VIR_MOCK_IMPL_RET_VOID(name, rettype) \
rettype name(void); \
static rettype (*real_##name)(void); \
rettype name(void)
# define VIR_MOCK_IMPL_VOID_ARGS(name, ...) \
void name(VIR_MOCK_ARGTYPENAMES(__VA_ARGS__)); \
static void (*real_##name)(VIR_MOCK_ARGTYPES(__VA_ARGS__)); \
void name(VIR_MOCK_ARGTYPENAMES_UNUSED(__VA_ARGS__))
# define VIR_MOCK_IMPL_VOID_VOID(name) \
void name(void); \
static void (*real_##name)(void); \
void name(void)
/*
* The VIR_MOCK_WRAP_NNN_MMM() macros are intended for use in the
* individual test suites. The define a stub implementation of
* the wrapped method and insert the caller provided code snippet
* as the body of the method.
*/
# define VIR_MOCK_WRAP_RET_ARGS(name, rettype, ...) \
rettype wrap_##name(VIR_MOCK_ARGTYPENAMES(__VA_ARGS__)); \
static rettype (*real_##name)(VIR_MOCK_ARGTYPES(__VA_ARGS__)); \
rettype wrap_##name(VIR_MOCK_ARGTYPENAMES_UNUSED(__VA_ARGS__))
# define VIR_MOCK_WRAP_RET_VOID(name, rettype) \
rettype wrap_##name(void); \
static rettype (*real_##name)(void); \
rettype wrap_##name(void)
# define VIR_MOCK_WRAP_VOID_ARGS(name, ...) \
void wrap_##name(VIR_MOCK_ARGTYPENAMES(__VA_ARGS__)); \
static void (*real_##name)(VIR_MOCK_ARGTYPES(__VA_ARGS__)); \
void wrap_##name(VIR_MOCK_ARGTYPENAMES_UNUSED(__VA_ARGS__))
# define VIR_MOCK_WRAP_VOID_VOID(name) \
void wrap_##name(void); \
static void (*real_##name)(void); \
void wrap_##name(void)
# define VIR_MOCK_REAL_INIT(name) \
do { \
if (real_##name == NULL && \
!(real_##name = dlsym(RTLD_NEXT, \
#name))) { \
fprintf(stderr, "Missing symbol '" #name "'\n"); \
abort(); \
} \
} while (0)
#endif /* LIBVIRT_VIRMOCK_H */