kernel/linux.git/scripts/genksyms/genksyms.c, branch linux-7.0.y

genksyms: Fix enum consts from a reference affecting new values

2025-06-07T05:38:07+00:00

Enumeration constants read from a symbol reference file can incorrectly affect new enumeration constants parsed from an actual input file. Example: $ cat test.c enum { E_A, E_B, E_MAX }; struct bar { int mem[E_MAX]; }; int foo(struct bar *a) {} __GENKSYMS_EXPORT_SYMBOL(foo); $ cat test.c | ./scripts/genksyms/genksyms -T test.0.symtypes #SYMVER foo 0x070d854d $ cat test.0.symtypes E#E_MAX 2 s#bar struct bar { int mem [ E#E_MAX ] ; } foo int foo ( s#bar * ) $ cat test.c | ./scripts/genksyms/genksyms -T test.1.symtypes -r test.0.symtypes :4: warning: foo: modversion changed because of changes in enum constant E_MAX #SYMVER foo 0x9c9dfd81 $ cat test.1.symtypes E#E_MAX ( 2 ) + 3 s#bar struct bar { int mem [ E#E_MAX ] ; } foo int foo ( s#bar * ) The __add_symbol() function includes logic to handle the incrementation of enumeration values, but this code is also invoked when reading a reference file. As a result, the variables last_enum_expr and enum_counter might be incorrectly set after reading the reference file, which later affects parsing of the actual input. Fix the problem by splitting the logic for the incrementation of enumeration values into a separate function process_enum() and call it from __add_symbol() only when processing non-reference data. Fixes: e37ddb825003 ("genksyms: Track changes to enum constants") Signed-off-by: Petr Pavlu Signed-off-by: Masahiro Yamada

genksyms: use uint32_t instead of unsigned long for calculating CRC

2025-01-10T14:01:22+00:00

Currently, 'unsigned long' is used for intermediate variables when calculating CRCs. The size of 'long' differs depending on the architecture: it is 32 bits on 32-bit architectures and 64 bits on 64-bit architectures. The CRC values generated by genksyms represent the compatibility of exported symbols. Therefore, reproducibility is important. In other words, we need to ensure that the output is the same when the kernel source is identical, regardless of whether genksyms is running on a 32-bit or 64-bit build machine. Fortunately, the output from genksyms is not affected by the build machine's architecture because only the lower 32 bits of the 'unsigned long' variables are used. To make it even clearer that the CRC calculation is independent of the build machine's architecture, this commit explicitly uses the fixed-width type, uint32_t. Signed-off-by: Masahiro Yamada

genksyms: use generic macros for hash table implementation

2025-01-10T14:01:22+00:00

Use macros provided by hashtable.h Signed-off-by: Masahiro Yamada

genksyms: refactor the return points in the for-loop in __add_symbol()

2025-01-10T14:01:22+00:00

free_list() must be called before returning from this for-loop. Swap 'break' and the combination of free_list() and 'return'. This reduces the code and minimizes the risk of introducing memory leaks in future changes. Signed-off-by: Masahiro Yamada

genksyms: reduce the indentation in the for-loop in __add_symbol()

2025-01-10T14:01:22+00:00

To improve readability, reduce the indentation as follows: - Use 'continue' earlier when the symbol does not match - flip !sym->is_declared to flatten the if-else chain No functional changes are intended. Signed-off-by: Masahiro Yamada

genksyms: fix memory leak when the same symbol is read from *.symref file

2025-01-10T14:01:22+00:00

When a symbol that is already registered is read again from *.symref file, __add_symbol() removes the previous one from the hash table without freeing it. [Test Case] $ cat foo.c #include void foo(void); void foo(void) {} EXPORT_SYMBOL(foo); $ cat foo.symref foo void foo ( void ) foo void foo ( void ) When a symbol is removed from the hash table, it must be freed along with its ->name and ->defn members. However, sym->name cannot be freed because it is sometimes shared with node->string, but not always. If sym->name and node->string share the same memory, free(sym->name) could lead to a double-free bug. To resolve this issue, always assign a strdup'ed string to sym->name. Fixes: 64e6c1e12372 ("genksyms: track symbol checksum changes") Signed-off-by: Masahiro Yamada

genksyms: fix memory leak when the same symbol is added from source

2025-01-10T14:01:22+00:00

When a symbol that is already registered is added again, __add_symbol() returns without freeing the symbol definition, making it unreachable. The following test cases demonstrate different memory leak points. [Test Case 1] Forward declaration with exactly the same definition $ cat foo.c #include void foo(void); void foo(void) {} EXPORT_SYMBOL(foo); [Test Case 2] Forward declaration with a different definition (e.g. attribute) $ cat foo.c #include void foo(void); __attribute__((__section__(".ref.text"))) void foo(void) {} EXPORT_SYMBOL(foo); [Test Case 3] Preserving an overridden symbol (compile with KBUILD_PRESERVE=1) $ cat foo.c #include void foo(void); void foo(void) { } EXPORT_SYMBOL(foo); $ cat foo.symref override foo void foo ( int ) The memory leaks in Test Case 1 and 2 have existed since the introduction of genksyms into the kernel tree. [1] The memory leak in Test Case 3 was introduced by commit 5dae9a550a74 ("genksyms: allow to ignore symbol checksum changes"). When multiple init_declarators are reduced to an init_declarator_list, the decl_spec must be duplicated. Otherwise, the following Test Case 4 would result in a double-free bug. [Test Case 4] $ cat foo.c #include extern int foo, bar; int foo, bar; EXPORT_SYMBOL(foo); In this case, 'foo' and 'bar' share the same decl_spec, 'int'. It must be unshared before being passed to add_symbol(). [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=46bd1da672d66ccd8a639d3c1f8a166048cca608 Fixes: 5dae9a550a74 ("genksyms: allow to ignore symbol checksum changes") Signed-off-by: Masahiro Yamada

genksyms: reduce indentation in export_symbol()

2024-11-27T23:46:02+00:00

Modify this function to return earlier when find_symbol() returns NULL, reducing the level of improve readability. No functional changes are intended. Signed-off-by: Masahiro Yamada

genksyms: use getopt_long() unconditionally

2023-11-28T02:22:50+00:00

getopt_long() is used by various tools in the kernel (e.g. Kconfig). It should be fine to use it all the time. Signed-off-by: Masahiro Yamada

genksyms: remove the remnant of the -s option

2023-11-28T02:22:50+00:00

Commit 74d931716151 ("genksyms: remove symbol prefix support") removed the -s (--symbol-prefix) option. Clean up the left-over. Signed-off-by: Masahiro Yamada