On Wed, Apr 14, 2021 at 11:48 AM <ojeda@xxxxxxxxxx> wrote:
>
> From: Miguel Ojeda <ojeda@xxxxxxxxxx>
>
> Rust symbols can become quite long due to namespacing introduced
> by modules, types, traits, generics, etc. For instance, for:
>
> pub mod my_module {
> pub struct MyType;
> pub struct MyGenericType<T>(T);
>
> pub trait MyTrait {
> fn my_method() -> u32;
> }
>
> impl MyTrait for MyGenericType<MyType> {
> fn my_method() -> u32 {
> 42
> }
> }
> }
>
> generates a symbol of length 96 when using the upcoming v0 mangling scheme:
>
> _RNvXNtCshGpAVYOtgW1_7example9my_moduleINtB2_13MyGenericTypeNtB2_6MyTypeENtB2_7MyTrait9my_method
>
> At the moment, Rust symbols may reach up to 300 in length.
> Setting 512 as the maximum seems like a reasonable choice to
> keep some headroom.
What are the implications of this change for someone not using Rust?
Does it change the binary size of vmlinux for a defconfig build, for
example?
>
> Co-developed-by: Alex Gaynor <alex.gaynor@xxxxxxxxx>
> Signed-off-by: Alex Gaynor <alex.gaynor@xxxxxxxxx>
> Co-developed-by: Geoffrey Thomas <geofft@xxxxxxxxxxxxx>
> Signed-off-by: Geoffrey Thomas <geofft@xxxxxxxxxxxxx>
> Co-developed-by: Finn Behrens <me@xxxxxxxxx>
> Signed-off-by: Finn Behrens <me@xxxxxxxxx>
> Co-developed-by: Adam Bratschi-Kaye <ark.email@xxxxxxxxx>
> Signed-off-by: Adam Bratschi-Kaye <ark.email@xxxxxxxxx>
> Co-developed-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx>
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> ---
> include/linux/kallsyms.h | 2 +-
> kernel/livepatch/core.c | 4 ++--
> scripts/kallsyms.c | 2 +-
> tools/include/linux/kallsyms.h | 2 +-
> tools/include/linux/lockdep.h | 2 +-
> tools/lib/perf/include/perf/event.h | 2 +-
> tools/lib/symbol/kallsyms.h | 2 +-
> 7 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
> index 465060acc981..5cdc6903abca 100644
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -14,7 +14,7 @@
>
> #include <asm/sections.h>
>
> -#define KSYM_NAME_LEN 128
> +#define KSYM_NAME_LEN 512
> #define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s]") + (KSYM_NAME_LEN - 1) + \
> 2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + 1)
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 335d988bd811..73874e5edfda 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -213,7 +213,7 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
> * we use the smallest/strictest upper bound possible (56, based on
> * the current definition of MODULE_NAME_LEN) to prevent overflows.
> */
> - BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
> + BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
>
> relas = (Elf_Rela *) relasec->sh_addr;
> /* For each rela in this klp relocation section */
> @@ -227,7 +227,7 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
>
> /* Format: .klp.sym.sym_objname.sym_name,sympos */
> cnt = sscanf(strtab + sym->st_name,
> - ".klp.sym.%55[^.].%127[^,],%lu",
> + ".klp.sym.%55[^.].%511[^,],%lu",
> sym_objname, sym_name, &sympos);
> if (cnt != 3) {
> pr_err("symbol %s has an incorrectly formatted name\n",
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index bcdabee13aab..9bab5f55ade3 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -27,7 +27,7 @@
>
> #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
>
> -#define KSYM_NAME_LEN 128
> +#define KSYM_NAME_LEN 512
>
> struct sym_entry {
> unsigned long long addr;
> diff --git a/tools/include/linux/kallsyms.h b/tools/include/linux/kallsyms.h
> index efb6c3f5f2a9..5a37ccbec54f 100644
> --- a/tools/include/linux/kallsyms.h
> +++ b/tools/include/linux/kallsyms.h
> @@ -6,7 +6,7 @@
> #include <stdio.h>
> #include <unistd.h>
>
> -#define KSYM_NAME_LEN 128
> +#define KSYM_NAME_LEN 512
>
> struct module;
>
> diff --git a/tools/include/linux/lockdep.h b/tools/include/linux/lockdep.h
> index e56997288f2b..d9c163f3ab24 100644
> --- a/tools/include/linux/lockdep.h
> +++ b/tools/include/linux/lockdep.h
> @@ -47,7 +47,7 @@ static inline int debug_locks_off(void)
>
> #define task_pid_nr(tsk) ((tsk)->pid)
>
> -#define KSYM_NAME_LEN 128
> +#define KSYM_NAME_LEN 512
> #define printk(...) dprintf(STDOUT_FILENO, __VA_ARGS__)
> #define pr_err(format, ...) fprintf (stderr, format, ## __VA_ARGS__)
> #define pr_warn pr_err
> diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
> index d82054225fcc..f5c40325b441 100644
> --- a/tools/lib/perf/include/perf/event.h
> +++ b/tools/lib/perf/include/perf/event.h
> @@ -93,7 +93,7 @@ struct perf_record_throttle {
> };
>
> #ifndef KSYM_NAME_LEN
> -#define KSYM_NAME_LEN 256
> +#define KSYM_NAME_LEN 512
> #endif
>
> struct perf_record_ksymbol {
> diff --git a/tools/lib/symbol/kallsyms.h b/tools/lib/symbol/kallsyms.h
> index 72ab9870454b..542f9b059c3b 100644
> --- a/tools/lib/symbol/kallsyms.h
> +++ b/tools/lib/symbol/kallsyms.h
> @@ -7,7 +7,7 @@
> #include <linux/types.h>
>
> #ifndef KSYM_NAME_LEN
> -#define KSYM_NAME_LEN 256
> +#define KSYM_NAME_LEN 512
> #endif
>
> static inline u8 kallsyms2elf_binding(char type)
> --
> 2.17.1
>
--
Thanks,
~Nick Desaulniers
