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[libc] Replace linker_assert() with build_assert()

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We currently implement build-time assertions via a mechanism that
generates a call to an undefined external function that will cause the
link to fail unless the compiler can prove that the asserted condition
is true (and thereby eliminate the undefined function call).

This assertion mechanism can be used for conditions that are not
amenable to the use of static_assert(), since static_assert() will not
allow for proofs via dead code elimination.

Add __attribute__((error(...))) to the undefined external function, so
that the error is raised at compile time rather than at link time.
This allows us to provide a more meaningful error message (which will
include the file name and line number, as with any other compile-time
error), and avoids the need for the caller to specify a unique symbol
name for the external function.

Change the name from linker_assert() to build_assert(), since the
assertion now takes place at compile time rather than at link time.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2024-01-16 13:24:29 +00:00
parent 6d29415c89
commit 4b7d9a6af0
12 changed files with 78 additions and 87 deletions
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8
src/crypto/gcm.c
View File

@@ -472,10 +472,10 @@ void gcm_setiv ( struct gcm_context *context, const void *iv, size_t ivlen ) {
union gcm_block *check = ( ( void * ) context );
/* Sanity checks */
linker_assert ( &context->hash == check, gcm_bad_layout );
linker_assert ( &context->len == check + 1, gcm_bad_layout );
linker_assert ( &context->ctr == check + 2, gcm_bad_layout );
linker_assert ( &context->key == check + 3, gcm_bad_layout );
build_assert ( &context->hash == check );
build_assert ( &context->len == check + 1 );
build_assert ( &context->ctr == check + 2 );
build_assert ( &context->key == check + 3 );
/* Reset non-key state */
memset ( context, 0, offsetof ( typeof ( *context ), key ) );

10
src/crypto/md4.c
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@@ -155,11 +155,11 @@ static void md4_digest ( struct md4_context *context ) {
/* Sanity checks */
assert ( ( context->len % sizeof ( context->ddd.dd.data ) ) == 0 );
linker_assert ( &u.ddd.dd.digest.h[0] == a, md4_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[1] == b, md4_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[2] == c, md4_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[3] == d, md4_bad_layout );
linker_assert ( &u.ddd.dd.data.dword[0] == w, md4_bad_layout );
build_assert ( &u.ddd.dd.digest.h[0] == a );
build_assert ( &u.ddd.dd.digest.h[1] == b );
build_assert ( &u.ddd.dd.digest.h[2] == c );
build_assert ( &u.ddd.dd.digest.h[3] == d );
build_assert ( &u.ddd.dd.data.dword[0] == w );
DBGC ( context, "MD4 digesting:\n" );
DBGC_HDA ( context, 0, &context->ddd.dd.digest,

10
src/crypto/md5.c
View File

@@ -178,11 +178,11 @@ static void md5_digest ( struct md5_context *context ) {
/* Sanity checks */
assert ( ( context->len % sizeof ( context->ddd.dd.data ) ) == 0 );
linker_assert ( &u.ddd.dd.digest.h[0] == a, md5_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[1] == b, md5_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[2] == c, md5_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[3] == d, md5_bad_layout );
linker_assert ( &u.ddd.dd.data.dword[0] == w, md5_bad_layout );
build_assert ( &u.ddd.dd.digest.h[0] == a );
build_assert ( &u.ddd.dd.digest.h[1] == b );
build_assert ( &u.ddd.dd.digest.h[2] == c );
build_assert ( &u.ddd.dd.digest.h[3] == d );
build_assert ( &u.ddd.dd.data.dword[0] == w );
DBGC ( context, "MD5 digesting:\n" );
DBGC_HDA ( context, 0, &context->ddd.dd.digest,

12
src/crypto/sha1.c
View File

@@ -145,12 +145,12 @@ static void sha1_digest ( struct sha1_context *context ) {
/* Sanity checks */
assert ( ( context->len % sizeof ( context->ddd.dd.data ) ) == 0 );
linker_assert ( &u.ddd.dd.digest.h[0] == a, sha1_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[1] == b, sha1_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[2] == c, sha1_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[3] == d, sha1_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[4] == e, sha1_bad_layout );
linker_assert ( &u.ddd.dd.data.dword[0] == w, sha1_bad_layout );
build_assert ( &u.ddd.dd.digest.h[0] == a );
build_assert ( &u.ddd.dd.digest.h[1] == b );
build_assert ( &u.ddd.dd.digest.h[2] == c );
build_assert ( &u.ddd.dd.digest.h[3] == d );
build_assert ( &u.ddd.dd.digest.h[4] == e );
build_assert ( &u.ddd.dd.data.dword[0] == w );
DBGC ( context, "SHA1 digesting:\n" );
DBGC_HDA ( context, 0, &context->ddd.dd.digest,

18
src/crypto/sha256.c
View File

@@ -140,15 +140,15 @@ static void sha256_digest ( struct sha256_context *context ) {
/* Sanity checks */
assert ( ( context->len % sizeof ( context->ddd.dd.data ) ) == 0 );
linker_assert ( &u.ddd.dd.digest.h[0] == a, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[1] == b, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[2] == c, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[3] == d, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[4] == e, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[5] == f, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[6] == g, sha256_bad_layout );
linker_assert ( &u.ddd.dd.digest.h[7] == h, sha256_bad_layout );
linker_assert ( &u.ddd.dd.data.dword[0] == w, sha256_bad_layout );
build_assert ( &u.ddd.dd.digest.h[0] == a );
build_assert ( &u.ddd.dd.digest.h[1] == b );
build_assert ( &u.ddd.dd.digest.h[2] == c );
build_assert ( &u.ddd.dd.digest.h[3] == d );
build_assert ( &u.ddd.dd.digest.h[4] == e );
build_assert ( &u.ddd.dd.digest.h[5] == f );
build_assert ( &u.ddd.dd.digest.h[6] == g );
build_assert ( &u.ddd.dd.digest.h[7] == h );
build_assert ( &u.ddd.dd.data.dword[0] == w );
DBGC ( context, "SHA256 digesting:\n" );
DBGC_HDA ( context, 0, &context->ddd.dd.digest,

18
src/crypto/sha512.c
View File

@@ -156,15 +156,15 @@ static void sha512_digest ( struct sha512_context *context ) {
/* Sanity checks */
assert ( ( context->len % sizeof ( context->ddq.dd.data ) ) == 0 );
linker_assert ( &u.ddq.dd.digest.h[0] == a, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[1] == b, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[2] == c, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[3] == d, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[4] == e, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[5] == f, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[6] == g, sha512_bad_layout );
linker_assert ( &u.ddq.dd.digest.h[7] == h, sha512_bad_layout );
linker_assert ( &u.ddq.dd.data.qword[0] == w, sha512_bad_layout );
build_assert ( &u.ddq.dd.digest.h[0] == a );
build_assert ( &u.ddq.dd.digest.h[1] == b );
build_assert ( &u.ddq.dd.digest.h[2] == c );
build_assert ( &u.ddq.dd.digest.h[3] == d );
build_assert ( &u.ddq.dd.digest.h[4] == e );
build_assert ( &u.ddq.dd.digest.h[5] == f );
build_assert ( &u.ddq.dd.digest.h[6] == g );
build_assert ( &u.ddq.dd.digest.h[7] == h );
build_assert ( &u.ddq.dd.data.qword[0] == w );
DBGC ( context, "SHA512 digesting:\n" );
DBGC_HDA ( context, 0, &context->ddq.dd.digest,