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From: Matthew Wilcox <willy@infradead.org>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Miguel Ojeda <ojeda@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	rust-for-linux <rust-for-linux@vger.kernel.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Geoffrey Thomas <geofft@ldpreload.com>,
	Finn Behrens <me@kloenk.de>,
	Adam Bratschi-Kaye <ark.email@gmail.com>,
	Wedson Almeida Filho <wedsonaf@google.com>
Subject: Re: [PATCH 01/17] kallsyms: support big kernel symbols (2-byte lengths)
Date: Sun, 4 Jul 2021 22:33:39 +0100	[thread overview]
Message-ID: <YOIpM3iFT5roz69i@casper.infradead.org> (raw)
In-Reply-To: <CANiq72=eHs870jbmZz8CUEUuN2NOCaKS9-F6-jAb0QXje2x1Eg@mail.gmail.com>

On Sun, Jul 04, 2021 at 11:17:50PM +0200, Miguel Ojeda wrote:
> On Sun, Jul 4, 2021 at 11:05 PM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > What happened to my suggestion from last time of encoding symbols < 128
> > as 0-127 and symbols larger than that as (data[0] - 128) * 256 +
> > data[1]) ?
> 
> Nothing, sorry, we focused on other parts (e.g. the allocation panics)
> during this iteration. I can take a look for v2.

Here's what I have.  Build testing now.


diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index c851ca0ed357..0d45a6e5fdc3 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -67,6 +67,14 @@ static unsigned int kallsyms_expand_symbol(unsigned int off,
 	len = *data;
 	data++;
 
+	/* lengths larger than 128 are encoded as two bytes */
+	if (len >= 128) {
+		len -= 128;
+		len *= 256;
+		len += *data;
+		data++;
+	}
+
 	/*
 	 * Update the offset to return the offset for the next symbol on
 	 * the compressed stream.
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 54ad86d13784..701566e01a1d 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -467,10 +467,16 @@ static void write_src(void)
 	output_label("kallsyms_names");
 	off = 0;
 	for (i = 0; i < table_cnt; i++) {
+		int len = table[i]->len;
 		if ((i & 0xFF) == 0)
 			markers[i >> 8] = off;
 
-		printf("\t.byte 0x%02x", table[i]->len);
+		if (len >= 128) {
+			printf("\t.byte 0x%02x\n", len / 256 + 128);
+			len %= 256;
+			off++;
+		}
+		printf("\t.byte 0x%02x", len);
 		for (k = 0; k < table[i]->len; k++)
 			printf(", 0x%02x", table[i]->sym[k]);
 		printf("\n");

  reply	other threads:[~2021-07-04 21:34 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-04 20:27 [PATCH 00/17] Rust support ojeda
2021-07-04 20:27 ` [PATCH 01/17] kallsyms: support big kernel symbols (2-byte lengths) ojeda
2021-07-04 20:52   ` Linus Torvalds
2021-07-04 21:15     ` Miguel Ojeda
2021-07-04 21:28       ` Linus Torvalds
2021-07-04 21:04   ` Matthew Wilcox
2021-07-04 21:17     ` Miguel Ojeda
2021-07-04 21:33       ` Matthew Wilcox [this message]
2021-07-04 21:49         ` Matthew Wilcox
2021-07-04 22:07           ` Miguel Ojeda
2021-07-04 22:20         ` Gary Guo
2021-07-04 22:42           ` Matthew Wilcox
2021-07-04 23:14             ` Gary Guo
2021-07-13 18:02             ` Kent Overstreet
2021-07-04 21:20     ` Gary Guo
2021-07-05  4:35       ` Willy Tarreau
2021-07-04 20:27 ` [PATCH 02/17] kallsyms: increase maximum kernel symbol length to 512 ojeda
2021-07-14 18:20   ` Nick Desaulniers
2021-07-14 19:04     ` Linus Torvalds
2021-07-14 20:09       ` Eric W. Biederman
2021-07-14 20:21         ` Linus Torvalds
2021-07-14 20:48           ` Eric W. Biederman
2021-07-14 22:40             ` Linus Torvalds
2021-07-14 20:19     ` Miguel Ojeda
2021-07-04 20:27 ` [PATCH 03/17] Makefile: generate `CLANG_FLAGS` even in GCC builds ojeda
2021-07-14 18:13   ` Nick Desaulniers
2021-07-14 18:16     ` Nick Desaulniers
2021-07-14 20:31     ` Miguel Ojeda
2021-07-04 20:27 ` [PATCH 04/17] vsprintf: add new `%pA` format specifier ojeda
2021-07-07 20:31   ` Nick Desaulniers
2021-07-07 22:33     ` Miguel Ojeda
2021-07-04 20:27 ` [PATCH 05/17] rust: add C helpers ojeda
2021-07-07 10:19   ` Marco Elver
2021-07-09 10:31     ` Marco Elver
2021-07-09 14:32     ` Miguel Ojeda
2021-07-04 20:27 ` [PATCH 06/17] rust: add `compiler_builtins` crate ojeda
2021-07-04 20:27 ` [PATCH 07/17] rust: add `alloc` crate ojeda
2021-07-04 20:27 ` [PATCH 08/17] rust: add `build_error` crate ojeda
2021-07-04 20:27 ` [PATCH 09/17] rust: add `macros` crate ojeda
2021-07-04 20:27 ` [PATCH 10/17] rust: add `kernel` crate ojeda
2021-07-04 20:27 ` [PATCH 11/17] rust: export generated symbols ojeda
2021-07-04 20:27 ` [PATCH 12/17] Kbuild: add Rust support ojeda
2021-07-04 20:27 ` [PATCH 13/17] docs: add Rust documentation ojeda
2021-07-05  5:02   ` Willy Tarreau
2021-07-06  0:06     ` Miguel Ojeda
2021-07-06  2:09       ` Willy Tarreau
2021-07-14 18:37   ` Nick Desaulniers
2021-07-14 19:55     ` Miguel Ojeda
2021-07-04 20:27 ` [PATCH 14/17] samples: add Rust examples ojeda
2021-07-04 20:27 ` [PATCH 15/17] scripts: add `generate_rust_analyzer.py` ojeda
2021-07-05  5:05   ` Willy Tarreau
2021-07-05 23:41     ` Miguel Ojeda
2021-07-04 20:27 ` [PATCH 16/17] MAINTAINERS: Rust ojeda
2021-07-06  0:26   ` Pedro Tammela
2021-07-06 22:14     ` Miguel Ojeda
2021-07-04 20:27 ` [RFC PATCH 17/17] Android: Binder IPC in Rust (WIP) ojeda
2021-07-04 23:11 ` [PATCH 00/17] Rust support Miguel Ojeda
2021-07-07  6:43 ` Christoph Hellwig
2021-07-07 12:33   ` Miguel Ojeda
2021-07-07 12:50     ` Greg Kroah-Hartman
2021-07-07 14:07       ` Wedson Almeida Filho
2021-07-07 14:12         ` Christoph Hellwig
2021-07-07 15:02         ` Greg Kroah-Hartman
2021-07-07 20:56           ` Finn Behrens
2021-07-08  0:58             ` Matthew Wilcox
2021-07-08  6:39               ` [PATCH 00/17] Rust support, NVMe Geert Stappers
2021-07-08  8:29                 ` Finn Behrens
2021-07-22 22:55               ` [PATCH 00/17] Rust support Wedson Almeida Filho
2021-07-23  1:17                 ` Matthew Wilcox
2021-07-23 11:33                   ` [PATCH 00/17] Rust support, GPIO driver Geert Stappers
2021-07-23 15:08                 ` [PATCH 00/17] Rust support Keith Busch
2021-07-07 10:51 ` Marco Elver
2021-07-07 11:28   ` Miguel Ojeda

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