kernel/linux.git/scripts/gendwarfksyms, branch v6.18.21

gendwarfksyms: Fix build on 32-bit hosts

2026-03-04T12:19:40+00:00

[ Upstream commit ddc54f912a551f6eb0bbcfc3880f45fe27a252cb ] We have interchangeably used unsigned long for some of the types defined in elfutils, assuming they're always 64-bit. This obviously fails when building gendwarfksyms on 32-bit hosts. Fix the types. Reported-by: Michal Suchánek Closes: https://lore.kernel.org/linux-modules/aRcxzPxtJblVSh1y@kitsune.suse.cz/ Tested-by: Michal Suchánek Signed-off-by: Sami Tolvanen Signed-off-by: Sasha Levin

gendwarfksyms: Skip files with no exports

2025-11-11T19:37:11+00:00

Starting with Rust 1.91.0 (released 2025-10-30), in upstream commit ab91a63d403b ("Ignore intrinsic calls in cross-crate-inlining cost model") [1][2], `bindings.o` stops containing DWARF debug information because the `Default` implementations contained `write_bytes()` calls which are now ignored in that cost model (note that `CLIPPY=1` does not reproduce it). This means `gendwarfksyms` complains: RUSTC L rust/bindings.o error: gendwarfksyms: process_module: dwarf_get_units failed: no debugging information? There are several alternatives that would work here: conditionally skipping in the cases needed (but that is subtle and brittle), forcing DWARF generation with e.g. a dummy `static` (ugly and we may need to do it in several crates), skipping the call to the tool in the Kbuild command when there are no exports (fine) or teaching the tool to do so itself (simple and clean). Thus do the last one: don't attempt to process files if we have no symbol versions to calculate. [ I used the commit log of my patch linked below since it explained the root issue and expanded it a bit more to summarize the alternatives. - Miguel ] Cc: stable@vger.kernel.org # Needed in 6.17.y. Reported-by: Haiyue Wang Closes: https://lore.kernel.org/rust-for-linux/b8c1c73d-bf8b-4bf2-beb1-84ffdcd60547@163.com/ Suggested-by: Miguel Ojeda Link: https://lore.kernel.org/rust-for-linux/CANiq72nKC5r24VHAp9oUPR1HVPqT+=0ab9N0w6GqTF-kJOeiSw@mail.gmail.com/ Link: https://github.com/rust-lang/rust/commit/ab91a63d403b0105cacd72809cd292a72984ed99 [1] Link: https://github.com/rust-lang/rust/pull/145910 [2] Signed-off-by: Sami Tolvanen Tested-by: Haiyue Wang Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20251110131913.1789896-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda

gendwarfksyms: order -T symtypes output by name

2025-07-26T06:31:30+00:00

When writing symtypes information, we iterate through the entire hash table containing type expansions. The key order varies unpredictably as new entries are added, making it harder to compare symtypes between builds. Resolve this by sorting the type expansions by name before output. Signed-off-by: Giuliano Procida Acked-by: Greg Kroah-Hartman Reviewed-by: Sami Tolvanen Signed-off-by: Masahiro Yamada

gendwarfksyms: use preferred form of sizeof for allocation

2025-07-26T06:31:30+00:00

The preferred form is to use the variable being allocated to, rather than explicitly supplying a type name which might become stale. Also do this for memset. Suggested-by: Masahiro Yamada Signed-off-by: Giuliano Procida Reviewed-by: Sami Tolvanen Signed-off-by: Masahiro Yamada

gendwarfksyms: Fix structure type overrides

2025-06-15T15:49:48+00:00

As we always iterate through the entire die_map when expanding type strings, recursively processing referenced types in type_expand_child() is not actually necessary. Furthermore, the type_string kABI rule added in commit c9083467f7b9 ("gendwarfksyms: Add a kABI rule to override type strings") can fail to override type strings for structures due to a missing kabi_get_type_string() check in this function. Fix the issue by dropping the unnecessary recursion and moving the override check to type_expand(). Note that symbol versions are otherwise unchanged with this patch. Fixes: c9083467f7b9 ("gendwarfksyms: Add a kABI rule to override type strings") Reported-by: Giuliano Procida Signed-off-by: Sami Tolvanen Reviewed-by: Petr Pavlu Signed-off-by: Masahiro Yamada

gendwarfksyms: Add a kABI rule to override type strings

2025-05-25T09:12:23+00:00

In rare situations where distributions must make significant changes to otherwise opaque data structures that have inadvertently been included in the published ABI, keeping symbol versions stable using the existing kABI macros can become tedious. For example, Android decided to switch to a newer io_uring implementation in the 5.10 GKI kernel "to resolve a huge number of potential, and known, problems with the codebase," requiring "horrible hacks" with genksyms: "A number of the io_uring structures get used in other core kernel structures, only as "opaque" pointers, so there is not any real ABI breakage. But, due to the visibility of the structures going away, the CRC values of many scheduler variables and functions were changed." -- https://r.android.com/2425293 While these specific changes probably could have been hidden from gendwarfksyms using the existing kABI macros, this may not always be the case. Add a last resort kABI rule that allows distribution maintainers to fully override a type string for a symbol or a type. Also add a more informative error message in case we find a non-existent type references when calculating versions. Suggested-by: Giuliano Procida Signed-off-by: Sami Tolvanen Reviewed-by: Petr Pavlu Signed-off-by: Masahiro Yamada

gendwarfksyms: Add a kABI rule to override byte_size attributes

2025-05-25T09:12:22+00:00

A data structure can be partially opaque to modules if its allocation is handled by the core kernel, and modules only need to access some of its members. In this situation, it's possible to append new members to the structure without breaking the ABI, as long as the layout for the original members remains unchanged. For example, consider the following struct: struct s { unsigned long a; void *p; }; gendwarfksyms --stable --dump-dies produces the following type expansion: variable structure_type s { member base_type long unsigned int byte_size(8) encoding(7) a data_member_location(0) , member pointer_type { base_type void } byte_size(8) p data_member_location(8) } byte_size(16) To append new members, we can use the KABI_IGNORE() macro to hide them from gendwarfksyms --stable: struct s { /* old members with unchanged layout */ unsigned long a; void *p; /* new members not accessed by modules */ KABI_IGNORE(0, unsigned long n); }; However, we can't hide the fact that adding new members changes the struct size, as seen in the updated type string: variable structure_type s { member base_type long unsigned int byte_size(8) encoding(7) a data_member_location(0) , member pointer_type { base_type void } byte_size(8) p data_member_location(8) } byte_size(24) In order to support this use case, add a kABI rule that makes it possible to override the byte_size attribute for types: /* * struct s allocation is handled by the kernel, so * appending new members without changing the original * layout won't break the ABI. */ KABI_BYTE_SIZE(s, 16); This results in a type string that's unchanged from the original and therefore, won't change versions for symbols that reference the changed structure. Signed-off-by: Sami Tolvanen Reviewed-by: Petr Pavlu Signed-off-by: Masahiro Yamada

gendwarfksyms: Clean up kABI rule look-ups

2025-05-25T09:12:22+00:00

Reduce code duplication by moving kABI rule look-ups to separate functions. Signed-off-by: Sami Tolvanen Reviewed-by: Petr Pavlu Signed-off-by: Masahiro Yamada

gendwarfksyms: Add a separate pass to resolve FQNs

2025-03-15T12:16:11+00:00

Using dwarf_getscopes_die to resolve fully-qualified names turns out to be rather slow, and also results in duplicate scopes being processed, which doesn't help. Simply adding an extra pass to resolve names for all DIEs before processing exports is noticeably faster. For the object files with the most exports in a defconfig+Rust build, the performance improvement is consistently >50%: rust/bindings.o: 1038 exports before: 9.5980 +- 0.0183 seconds time elapsed ( +- 0.19% ) after: 4.3116 +- 0.0287 seconds time elapsed ( +- 0.67% ) rust/core.o: 424 exports before: 5.3584 +- 0.0204 seconds time elapsed ( +- 0.38% ) after: 0.05348 +- 0.00129 seconds time elapsed ( +- 2.42% ) ^ Not a mistake. net/core/dev.o: 190 exports before: 9.0507 +- 0.0297 seconds time elapsed ( +- 0.33% ) after: 3.2882 +- 0.0165 seconds time elapsed ( +- 0.50% ) rust/kernel.o: 129 exports before: 6.8571 +- 0.0317 seconds time elapsed ( +- 0.46% ) after: 2.9096 +- 0.0316 seconds time elapsed ( +- 1.09% ) net/core/skbuff.o: 120 exports before: 5.4805 +- 0.0291 seconds time elapsed ( +- 0.53% ) after: 2.0339 +- 0.0231 seconds time elapsed ( +- 1.14% ) drivers/gpu/drm/display/drm_dp_helper.o: 101 exports before: 1.7877 +- 0.0187 seconds time elapsed ( +- 1.05% ) after: 0.69245 +- 0.00994 seconds time elapsed ( +- 1.44% ) net/core/sock.o: 97 exports before: 5.8327 +- 0.0653 seconds time elapsed ( +- 1.12% ) after: 2.0784 +- 0.0291 seconds time elapsed ( +- 1.40% ) drivers/net/phy/phy_device.o: 95 exports before: 3.0671 +- 0.0371 seconds time elapsed ( +- 1.21% ) after: 1.2127 +- 0.0207 seconds time elapsed ( +- 1.70% ) drivers/pci/pci.o: 93 exports before: 1.1130 +- 0.0113 seconds time elapsed ( +- 1.01% ) after: 0.4848 +- 0.0127 seconds time elapsed ( +- 2.63% ) kernel/sched/core.o: 83 exports before: 3.5092 +- 0.0223 seconds time elapsed ( +- 0.64% ) after: 1.1231 +- 0.0145 seconds time elapsed ( +- 1.29% ) Overall, a defconfig+DWARF5 build with gendwarfksyms and Rust is 14.8% faster with this patch applied on my test system. Without Rust, there's still a 10.4% improvement in build time when gendwarfksyms is used. Note that symbol versions are unchanged with this patch. Suggested-by: Giuliano Procida Signed-off-by: Sami Tolvanen Signed-off-by: Masahiro Yamada

gendwarfksyms: Add support for symbol type pointers

2025-01-10T16:25:26+00:00

The compiler may choose not to emit type information in DWARF for external symbols. Clang, for example, does this for symbols not defined in the current TU. To provide a way to work around this issue, add support for __gendwarfksyms_ptr_ pointers that force the compiler to emit the necessary type information in DWARF also for the missing symbols. Example usage: #define GENDWARFKSYMS_PTR(sym) \ static typeof(sym) *__gendwarfksyms_ptr_##sym __used \ __section(".discard.gendwarfksyms") = &sym; extern int external_symbol(void); GENDWARFKSYMS_PTR(external_symbol); Signed-off-by: Sami Tolvanen Reviewed-by: Petr Pavlu Signed-off-by: Masahiro Yamada