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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 <gprocida@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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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 <gprocida@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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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 <gprocida@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Calculate symbol versions from the fully expanded type strings in
type_map, and output the versions in a genksyms-compatible format.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Add support for producing genksyms-style symtypes files. Process
die_map to find the longest expansions for each type, and use symtypes
references in type definitions. The basic file format is similar to
genksyms, with two notable exceptions:
1. Type names with spaces (common with Rust) in references are
wrapped in single quotes. E.g.:
s#'core::result::Result<u8, core::num::error::ParseIntError>'
2. The actual type definition is the simple parsed DWARF format we
output with --dump-dies, not the preprocessed C-style format
genksyms produces.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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