Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH v4 12/20] vsprintf: add new `%pA` format specifier | Date | Mon, 14 Feb 2022 11:36:58 +0000 |
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From: Rasmus Villemoes > Sent: 14 February 2022 10:53 > > On 14/02/2022 11.18, Andy Shevchenko wrote: > > On Sat, Feb 12, 2022 at 02:03:38PM +0100, Miguel Ojeda wrote: > > > >> From: Gary Guo <gary@garyguo.net> > > > > Not sure I understand this... > > > >> This patch adds a format specifier `%pA` to `vsprintf` which formats > >> a pointer as `core::fmt::Arguments`. Doing so allows us to directly > >> format to the internal buffer of `printf`, so we do not have to use > >> a temporary buffer on the stack to pre-assemble the message on > >> the Rust side. > >> > >> This specifier is intended only to be used from Rust and not for C, so > >> `checkpatch.pl` is intentionally unchanged to catch any misuse. > >> > >> Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com> > >> Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com> > >> Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com> > >> Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com> > > > >> Signed-off-by: Gary Guo <gary@garyguo.net> > > > > ...together with this in the current SoB chain. > > > >> Co-developed-by: Miguel Ojeda <ojeda@kernel.org> > >> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > > > > I'm wondering if you considered to use %pV. > > > > I think the point is for vsnprintf() to call (back) into Rust code.
Doesn't that stand a reasonable chance of blowing the kernel stack?
vsnprintf() is likely to be on the 'worst case' stack path anyway. Anything vaguely like a recursive call, or anything 'stack expensive' inside vsnprintf() stands a real chance of overflowing the stack.
David
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