Message-ID: <CAK7LNASAzsgmkWGOU7WWuBMmzG4vPRDQLjyW4sW+q46QZT=vnQ@mail.gmail.com>
Date: Thu, 29 Aug 2024 03:22:25 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Matthew Maurer <mmaurer@...gle.com>, 
	Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Gary Guo <gary@...yguo.net>, 
	Petr Pavlu <petr.pavlu@...e.com>, Neal Gompa <neal@...pa.dev>, Hector Martin <marcan@...can.st>, 
	Janne Grunau <j@...nau.net>, Asahi Linux <asahi@...ts.linux.dev>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 03/19] gendwarfksyms: Add address matching

On Fri, Aug 16, 2024 at 2:39 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> The compiler may choose not to emit type information in DWARF for all
> aliases, but it's possible for each alias to be exported separately.
> To ensure we find type information for the aliases as well, read
> {section, address} tuples from the symbol table and match symbols also
> by address.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>  scripts/gendwarfksyms/gendwarfksyms.c |   2 +
>  scripts/gendwarfksyms/gendwarfksyms.h |   7 ++
>  scripts/gendwarfksyms/symbols.c       | 161 +++++++++++++++++++++++++-
>  3 files changed, 165 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
> index d209b237766b..e2f8ee5a4bf3 100644
> --- a/scripts/gendwarfksyms/gendwarfksyms.c
> +++ b/scripts/gendwarfksyms/gendwarfksyms.c
> @@ -118,6 +118,8 @@ int main(int argc, const char **argv)
>                         return -1;
>                 }
>
> +               check(symbol_read_symtab(fd));
> +
>                 dwfl = dwfl_begin(&callbacks);
>                 if (!dwfl) {
>                         error("dwfl_begin failed for '%s': %s", object_files[n],
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
> index 03f3e408a839..cb9106dfddb9 100644
> --- a/scripts/gendwarfksyms/gendwarfksyms.h
> +++ b/scripts/gendwarfksyms/gendwarfksyms.h
> @@ -61,6 +61,10 @@ extern bool debug;
>  /*
>   * symbols.c
>   */
> +struct symbol_addr {
> +       uint32_t section;
> +       Elf64_Addr address;
> +};
>
>  static inline u32 name_hash(const char *name)
>  {
> @@ -69,10 +73,13 @@ static inline u32 name_hash(const char *name)
>
>  struct symbol {
>         const char *name;
> +       struct symbol_addr addr;
> +       struct hlist_node addr_hash;
>         struct hlist_node name_hash;
>  };
>
>  extern int symbol_read_exports(FILE *file);
> +extern int symbol_read_symtab(int fd);
>  extern struct symbol *symbol_get(const char *name);
>
>  /*
> diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
> index 673ad9cf9e77..f96acb941196 100644
> --- a/scripts/gendwarfksyms/symbols.c
> +++ b/scripts/gendwarfksyms/symbols.c
> @@ -6,11 +6,43 @@
>  #include "gendwarfksyms.h"
>
>  #define SYMBOL_HASH_BITS 15
> +
> +/* struct symbol_addr -> struct symbol */
> +static DEFINE_HASHTABLE(symbol_addrs, SYMBOL_HASH_BITS);
> +/* name -> struct symbol */
>  static DEFINE_HASHTABLE(symbol_names, SYMBOL_HASH_BITS);
>
> +static inline u32 symbol_addr_hash(const struct symbol_addr *addr)
> +{
> +       return jhash(addr, sizeof(struct symbol_addr), 0);
> +}
> +
>  typedef int (*symbol_callback_t)(struct symbol *, void *arg);
>
> -static int for_each(const char *name, symbol_callback_t func, void *data)
> +static int __for_each_addr(struct symbol *sym, symbol_callback_t func,
> +                          void *data)
> +{
> +       struct hlist_node *tmp;
> +       struct symbol *match = NULL;
> +       int processed = 0;
> +
> +       hash_for_each_possible_safe(symbol_addrs, match, tmp, addr_hash,
> +                                   symbol_addr_hash(&sym->addr)) {
> +               if (match == sym)
> +                       continue; /* Already processed */
> +
> +               if (match->addr.section == sym->addr.section &&
> +                   match->addr.address == sym->addr.address) {
> +                       check(func(match, data));
> +                       ++processed;
> +               }
> +       }
> +
> +       return processed;
> +}
> +
> +static int for_each(const char *name, bool name_only, symbol_callback_t func,
> +                   void *data)
>  {
>         struct hlist_node *tmp;
>         struct symbol *match;
> @@ -23,9 +55,13 @@ static int for_each(const char *name, symbol_callback_t func, void *data)
>                 if (strcmp(match->name, name))
>                         continue;
>
> +               /* Call func for the match, and all address matches */
>                 if (func)
>                         check(func(match, data));
>
> +               if (!name_only && match->addr.section != SHN_UNDEF)
> +                       return checkp(__for_each_addr(match, func, data)) + 1;
> +
>                 return 1;
>         }
>
> @@ -34,7 +70,7 @@ static int for_each(const char *name, symbol_callback_t func, void *data)
>
>  static bool is_exported(const char *name)
>  {
> -       return checkp(for_each(name, NULL, NULL)) > 0;
> +       return checkp(for_each(name, true, NULL, NULL)) > 0;
>  }
>
>  int symbol_read_exports(FILE *file)
> @@ -57,13 +93,14 @@ int symbol_read_exports(FILE *file)
>                 if (is_exported(name))
>                         continue; /* Ignore duplicates */
>
> -               sym = malloc(sizeof(struct symbol));
> +               sym = calloc(1, sizeof(struct symbol));



I am tired of noise changes when reviewing this patch set.


2/19 added malloc(), which is immediately replaced with calloc() by 3/19.










--
Best Regards

Masahiro Yamada

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