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Message-ID: <742f7226-9c66-4cfb-ba31-222dfb54fc34@suse.com>
Date: Wed, 28 Aug 2024 14:46:03 +0200
From: Petr Pavlu <petr.pavlu@...e.com>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
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 05/19] gendwarfksyms: Expand base_type
On 8/15/24 19:39, Sami Tolvanen wrote:
> Start making gendwarfksyms more useful by adding support for
> expanding DW_TAG_base_type types and basic DWARF attributes.
>
> Example:
>
> $ echo loops_per_jiffy | \
> scripts/gendwarfksyms/gendwarfksyms --debug vmlinux.o
> ...
> gendwarfksyms: process_exported_symbols: loops_per_jiffy
> variable base_type unsigned long byte_size(8) encoding(7);
> ...
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
> scripts/gendwarfksyms/dwarf.c | 121 +++++++++++++++++++++++++++++++++-
> 1 file changed, 120 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
> index 956b30224316..a37c9049d18e 100644
> --- a/scripts/gendwarfksyms/dwarf.c
> +++ b/scripts/gendwarfksyms/dwarf.c
> @@ -5,6 +5,17 @@
>
> #include "gendwarfksyms.h"
>
> +#define DEFINE_GET_ATTR(attr, type) \
> + static bool get_##attr##_attr(Dwarf_Die *die, unsigned int id, \
> + type *value) \
> + { \
> + Dwarf_Attribute da; \
> + return dwarf_attr(die, id, &da) && \
> + !dwarf_form##attr(&da, value); \
> + }
> +
> +DEFINE_GET_ATTR(udata, Dwarf_Word)
> +
> static bool get_ref_die_attr(Dwarf_Die *die, unsigned int id, Dwarf_Die *value)
> {
> Dwarf_Attribute da;
> @@ -60,6 +71,74 @@ static int process(struct state *state, const char *s)
> return 0;
> }
>
> +#define MAX_FMT_BUFFER_SIZE 128
> +
> +static int process_fmt(struct state *state, const char *fmt, ...)
Nit: The state parameter is unused by a number of these process_*()
functions, including the leaf process(). I suggest removing it so it
doesn't need to be passed around unnecessarily.
> +{
> + char buf[MAX_FMT_BUFFER_SIZE];
> + va_list args;
> + int res;
> +
> + va_start(args, fmt);
> +
> + res = checkp(vsnprintf(buf, sizeof(buf), fmt, args));
> + if (res >= MAX_FMT_BUFFER_SIZE - 1) {
This check looks off by one, though on the safe side:
res >= sizeof(buf)
> + error("vsnprintf overflow: increase MAX_FMT_BUFFER_SIZE");
> + res = -1;
> + } else {
> + res = check(process(state, buf));
> + }
> +
> + va_end(args);
> + return res;
> +}
> +
> +/* Process a fully qualified name from DWARF scopes */
> +static int process_fqn(struct state *state, Dwarf_Die *die)
> +{
> + Dwarf_Die *scopes = NULL;
> + const char *name;
> + int res;
> + int i;
> +
> + res = checkp(dwarf_getscopes_die(die, &scopes));
> + if (!res) {
> + name = get_name(die);
> + name = name ?: "<unnamed>";
> + return check(process(state, name));
> + }
> +
> + for (i = res - 1; i >= 0; i--) {
> + if (dwarf_tag(&scopes[i]) == DW_TAG_compile_unit)
> + continue;
> +
> + name = get_name(&scopes[i]);
> + name = name ?: "<unnamed>";
> + check(process(state, name));
> + if (i > 0)
> + check(process(state, "::"));
Failed check(process()) calls here return immediately and so would leak
scopes. However, I see this is fixed in the following patch
"gendwarfksyms: Add a cache for processed DIEs" so it's ok.
> + }
> +
> + free(scopes);
> + return 0;
> +}
> +
> +#define DEFINE_PROCESS_UDATA_ATTRIBUTE(attribute) \
> + static int process_##attribute##_attr(struct state *state, \
> + Dwarf_Die *die) \
> + { \
> + Dwarf_Word value; \
> + if (get_udata_attr(die, DW_AT_##attribute, &value)) \
> + check(process_fmt(state, \
> + " " #attribute "(%" PRIu64 ")", \
> + value)); \
> + return 0; \
> + }
> +
> +DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
> +DEFINE_PROCESS_UDATA_ATTRIBUTE(byte_size)
> +DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
> +
> bool match_all(Dwarf_Die *die)
> {
> return true;
> @@ -81,6 +160,44 @@ int process_die_container(struct state *state, Dwarf_Die *die,
> return 0;
> }
>
> +static int process_type(struct state *state, Dwarf_Die *die);
> +
> +static int process_type_attr(struct state *state, Dwarf_Die *die)
> +{
> + Dwarf_Die type;
> +
> + if (get_ref_die_attr(die, DW_AT_type, &type))
> + return check(process_type(state, &type));
> +
> + /* Compilers can omit DW_AT_type -- print out 'void' to clarify */
> + return check(process(state, "base_type void"));
> +}
> +
> +static int process_base_type(struct state *state, Dwarf_Die *die)
> +{
> + check(process(state, "base_type "));
> + check(process_fqn(state, die));
> + check(process_byte_size_attr(state, die));
> + check(process_encoding_attr(state, die));
> + return check(process_alignment_attr(state, die));
> +}
> +
> +static int process_type(struct state *state, Dwarf_Die *die)
> +{
> + int tag = dwarf_tag(die);
> +
> + switch (tag) {
> + case DW_TAG_base_type:
> + check(process_base_type(state, die));
> + break;
> + default:
> + debug("unimplemented type: %x", tag);
> + break;
> + }
> +
> + return 0;
> +}
> +
> /*
> * Exported symbol processing
> */
> @@ -91,7 +208,9 @@ static int process_subprogram(struct state *state, Dwarf_Die *die)
>
> static int process_variable(struct state *state, Dwarf_Die *die)
> {
> - return check(process(state, "variable;\n"));
> + check(process(state, "variable "));
> + check(process_type_attr(state, die));
> + return check(process(state, ";\n"));
> }
>
> static int process_symbol_ptr(struct state *state, Dwarf_Die *die)
--
Thanks,
Petr
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