From: Matthew Wilcox <willy@infradead.org>
To: Zheng Yejian <zhengyejian@huaweicloud.com>
Cc: arnd@arndb.de, kees@kernel.org, mcgrof@kernel.org,
masahiroy@kernel.org, ndesaulniers@google.com, ardb@kernel.org,
jannh@google.com, song@kernel.org, boqun.feng@gmail.com,
gregkh@linuxfoundation.org, gary@garyguo.net,
wedsonaf@google.com, linux-kernel@vger.kernel.org,
yeweihua4@huawei.com
Subject: Re: [PATCH v2] kallsyms: Fix wrong "big" kernel symbol type read from procfs
Date: Fri, 11 Oct 2024 23:01:12 +0100 [thread overview]
Message-ID: <ZwmgKHxgl2BQuKp6@casper.infradead.org> (raw)
In-Reply-To: <20241011143853.3022643-1-zhengyejian@huaweicloud.com>
On Fri, Oct 11, 2024 at 10:38:53PM +0800, Zheng Yejian wrote:
> The root cause is that, after commit 73bbb94466fd ("kallsyms: support
> "big" kernel symbols"), ULEB128 was used to encode symbol name length.
> That is, for "big" kernel symbols of which name length is longer than
> 0x7f characters, the length info is encoded into 2 bytes.
Technically, at least two. If we ever have a symbol larger than
16kB, we'll use three bytes.
> +++ b/kernel/kallsyms.c
> @@ -103,8 +103,11 @@ static char kallsyms_get_symbol_type(unsigned int off)
> {
> /*
> * Get just the first code, look it up in the token table,
> - * and return the first char from this token.
> + * and return the first char from this token. If MSB of length
> + * is 1, it is a "big" symbol, so needs an additional byte.
> */
> + if (kallsyms_names[off] & 0x80)
> + off++;
So this "if" should be a "while" for maximum future proofing against the
day that we have a 16kB function ...
next prev parent reply other threads:[~2024-10-11 22:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-11 14:38 Zheng Yejian
2024-10-11 14:08 ` Gary Guo
2024-10-11 22:01 ` Matthew Wilcox [this message]
2024-10-12 1:36 ` Zheng Yejian
2024-10-12 1:47 ` Gary Guo
2024-10-12 2:09 ` Zheng Yejian
2025-11-11 21:13 ` Miguel Ojeda
2025-11-16 22:30 ` Miguel Ojeda
2025-11-24 16:54 ` Miguel Ojeda
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