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| author | Jim Cromie <jim.cromie@gmail.com> | 2022-11-17 10:16:33 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-11-17 19:37:04 +0100 |
| commit | 1d926e259d8f8195fdfaeea7951149001894b473 (patch) | |
| tree | 5740bb8fdb511b85b69ad8ba3c0261f64d198369 | |
| parent | 435d6b6564568b82ec74ee7d4d0bcb1f24ccb5f5 (diff) | |
| download | linux-1d926e259d8f8195fdfaeea7951149001894b473.tar.bz2 | |
vmlinux.lds.h: add HEADERED_SECTION_* macros
These macros elaborate on BOUNDED_SECTION_(PRE|POST)_LABEL macros,
prepending an optional KEEP(.gnu.linkonce##_sec_) reservation, and a
linker-symbol to address it.
This allows a developer to define a header struct (which must fit with
the section's base struct-type), and could contain:
1- fields whose value is common to the entire set of data-records.
This allows the header & data structs to specialize, complement
each other, and shrink.
2- an uplink pointer to an organizing struct
which refs other related/sub data-tables
header record is addressable via the extern'd header linker-symbol
Once the linker-symbols created by the macro are ref'd extern in code,
that code can compute a record's index (ptr - start) in the "primary"
table, then use it to index into the related/sub tables. Adding a
primary.map_* field foreach sub-table would then allow deduplication
and remapping of that sub-table.
This is aimed at dyndbg's struct _ddebug __dyndbg[] section, whose 3
columns: function, file, module are 50%, 90%, 100% redundant. The
module column is fully recoverable after dynamic_debug_init() saves it
to each ddebug_table.module as the builtin __dyndbg[] table is parsed.
Given that those 3 columns use 24/56 of a _ddebug record, a dyndbg=y
kernel with ~5k callsites could reduce kernel memory substantially.
Returning that memory to the kernel buddy-allocator? is then possible.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20221117171633.923628-3-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | include/asm-generic/vmlinux.lds.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index c17f94785253..c9a475a30803 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -208,6 +208,21 @@ #define BOUNDED_SECTION(_sec) BOUNDED_SECTION_BY(_sec, _sec) +#define HEADERED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \ + _HDR_##_label_ = .; \ + KEEP(*(.gnu.linkonce.##_sec_)) \ + BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_) + +#define HEADERED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \ + _label_##_HDR_ = .; \ + KEEP(*(.gnu.linkonce.##_sec_)) \ + BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_) + +#define HEADERED_SECTION_BY(_sec_, _label_) \ + HEADERED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop) + +#define HEADERED_SECTION(_sec) HEADERED_SECTION_BY(_sec, _sec) + #ifdef CONFIG_TRACE_BRANCH_PROFILING #define LIKELY_PROFILE() \ BOUNDED_SECTION_BY(_ftrace_annotated_branch, _annotated_branch_profile) |