Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
On Fri, Mar 05, 2021 at 01:49:03PM +0100, Christophe Leroy wrote: > Le 05/03/2021 à 12:58, Michael Ellerman a écrit : > >prom_init runs as an OF client, with the MMU off (except on some Apple > >machines), and we don't own the MMU. So there's really nothing we can do :) > > > >Though now that I look at it, I don't think we should be doing this > >level of commandline handling in prom_init. It should just grab the > >value from firmware and pass it to the kernel proper, and then all the > >prepend/append/force etc. logic should happen there. > > But then, how do you handle the command line parameters that are needed by > prom_init ? > > For instance, prom_init_mem() use 'prom_memory_limit', which comes from the > "mem=" option in the command line. *Reading* it is easy, much easier than modifying it. Segher
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
On Fri, Mar 05, 2021 at 10:58:02PM +1100, Michael Ellerman wrote: > Will Deacon writes: > > That's very similar to us; we're not relocated, although we are at least > > in control of the MMU (which is using a temporary set of page-tables). > > prom_init runs as an OF client, with the MMU off (except on some Apple > machines), and we don't own the MMU. So there's really nothing we can do :) You *could* take over all memory mapping. This is complex, and I estimate the change you get this to work correctly on all supported systems to be between -400% and 0%. And not very long later Linux jettisons OF completely anyway. > Though now that I look at it, I don't think we should be doing this > level of commandline handling in prom_init. It should just grab the > value from firmware and pass it to the kernel proper, and then all the > prepend/append/force etc. logic should happen there. That sounds much simpler, yes :-) Segher
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
Le 05/03/2021 à 12:58, Michael Ellerman a écrit :
Will Deacon writes:
On Wed, Mar 03, 2021 at 06:57:09PM +0100, Christophe Leroy wrote:
Le 03/03/2021 à 18:46, Will Deacon a écrit :
On Wed, Mar 03, 2021 at 06:38:16PM +0100, Christophe Leroy wrote:
Le 03/03/2021 à 18:28, Will Deacon a écrit :
On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
This code provides architectures with a way to build command line
based on what is built in the kernel and what is handed over by the
bootloader, based on selected compile-time options.
Signed-off-by: Christophe Leroy
---
include/linux/cmdline.h | 62 +
1 file changed, 62 insertions(+)
create mode 100644 include/linux/cmdline.h
diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
new file mode 100644
index ..ae3610bb0ee2
--- /dev/null
+++ b/include/linux/cmdline.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CMDLINE_H
+#define _LINUX_CMDLINE_H
+
+static __always_inline size_t cmdline_strlen(const char *s)
+{
+ const char *sc;
+
+ for (sc = s; *sc != '\0'; ++sc)
+ ; /* nothing */
+ return sc - s;
+}
+
+static __always_inline size_t cmdline_strlcat(char *dest, const char *src,
size_t count)
+{
+ size_t dsize = cmdline_strlen(dest);
+ size_t len = cmdline_strlen(src);
+ size_t res = dsize + len;
+
+ /* This would be a bug */
+ if (dsize >= count)
+ return count;
+
+ dest += dsize;
+ count -= dsize;
+ if (len >= count)
+ len = count - 1;
+ memcpy(dest, src, len);
+ dest[len] = 0;
+ return res;
+}
Why are these needed instead of using strlen and strlcat directly?
Because on powerpc (at least), it will be used in prom_init, it is very
early in the boot and KASAN shadow memory is not set up yet so calling
generic string functions would crash the board.
Hmm. We deliberately setup a _really_ early shadow on arm64 for this, can
you not do something similar? Failing that, I think it would be better to
offer the option for an arch to implement cmdline_*, but have then point to
the normal library routines by default.
I don't think it is possible to setup an earlier early shadow.
At the point we are in prom_init, the code is not yet relocated at the
address it was linked for, and it is running with the MMU set by the
bootloader, I can't imagine being able to setup MMU entries for the early
shadow KASAN yet without breaking everything.
That's very similar to us; we're not relocated, although we are at least
in control of the MMU (which is using a temporary set of page-tables).
prom_init runs as an OF client, with the MMU off (except on some Apple
machines), and we don't own the MMU. So there's really nothing we can do :)
Though now that I look at it, I don't think we should be doing this
level of commandline handling in prom_init. It should just grab the
value from firmware and pass it to the kernel proper, and then all the
prepend/append/force etc. logic should happen there.
But then, how do you handle the command line parameters that are needed by
prom_init ?
For instance, prom_init_mem() use 'prom_memory_limit', which comes from the "mem=" option in the
command line.
Christophe
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
Will Deacon writes:
> On Wed, Mar 03, 2021 at 06:57:09PM +0100, Christophe Leroy wrote:
>> Le 03/03/2021 à 18:46, Will Deacon a écrit :
>> > On Wed, Mar 03, 2021 at 06:38:16PM +0100, Christophe Leroy wrote:
>> > > Le 03/03/2021 à 18:28, Will Deacon a écrit :
>> > > > On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
>> > > > > This code provides architectures with a way to build command line
>> > > > > based on what is built in the kernel and what is handed over by the
>> > > > > bootloader, based on selected compile-time options.
>> > > > >
>> > > > > Signed-off-by: Christophe Leroy
>> > > > > ---
>> > > > >include/linux/cmdline.h | 62
>> > > > > +
>> > > > >1 file changed, 62 insertions(+)
>> > > > >create mode 100644 include/linux/cmdline.h
>> > > > >
>> > > > > diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
>> > > > > new file mode 100644
>> > > > > index ..ae3610bb0ee2
>> > > > > --- /dev/null
>> > > > > +++ b/include/linux/cmdline.h
>> > > > > @@ -0,0 +1,62 @@
>> > > > > +/* SPDX-License-Identifier: GPL-2.0 */
>> > > > > +#ifndef _LINUX_CMDLINE_H
>> > > > > +#define _LINUX_CMDLINE_H
>> > > > > +
>> > > > > +static __always_inline size_t cmdline_strlen(const char *s)
>> > > > > +{
>> > > > > +const char *sc;
>> > > > > +
>> > > > > +for (sc = s; *sc != '\0'; ++sc)
>> > > > > +; /* nothing */
>> > > > > +return sc - s;
>> > > > > +}
>> > > > > +
>> > > > > +static __always_inline size_t cmdline_strlcat(char *dest, const
>> > > > > char *src, size_t count)
>> > > > > +{
>> > > > > +size_t dsize = cmdline_strlen(dest);
>> > > > > +size_t len = cmdline_strlen(src);
>> > > > > +size_t res = dsize + len;
>> > > > > +
>> > > > > +/* This would be a bug */
>> > > > > +if (dsize >= count)
>> > > > > +return count;
>> > > > > +
>> > > > > +dest += dsize;
>> > > > > +count -= dsize;
>> > > > > +if (len >= count)
>> > > > > +len = count - 1;
>> > > > > +memcpy(dest, src, len);
>> > > > > +dest[len] = 0;
>> > > > > +return res;
>> > > > > +}
>> > > >
>> > > > Why are these needed instead of using strlen and strlcat directly?
>> > >
>> > > Because on powerpc (at least), it will be used in prom_init, it is very
>> > > early in the boot and KASAN shadow memory is not set up yet so calling
>> > > generic string functions would crash the board.
>> >
>> > Hmm. We deliberately setup a _really_ early shadow on arm64 for this, can
>> > you not do something similar? Failing that, I think it would be better to
>> > offer the option for an arch to implement cmdline_*, but have then point to
>> > the normal library routines by default.
>>
>> I don't think it is possible to setup an earlier early shadow.
>>
>> At the point we are in prom_init, the code is not yet relocated at the
>> address it was linked for, and it is running with the MMU set by the
>> bootloader, I can't imagine being able to setup MMU entries for the early
>> shadow KASAN yet without breaking everything.
>
> That's very similar to us; we're not relocated, although we are at least
> in control of the MMU (which is using a temporary set of page-tables).
prom_init runs as an OF client, with the MMU off (except on some Apple
machines), and we don't own the MMU. So there's really nothing we can do :)
Though now that I look at it, I don't think we should be doing this
level of commandline handling in prom_init. It should just grab the
value from firmware and pass it to the kernel proper, and then all the
prepend/append/force etc. logic should happen there.
cheers
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
On Wed, Mar 03, 2021 at 06:57:09PM +0100, Christophe Leroy wrote:
> Le 03/03/2021 à 18:46, Will Deacon a écrit :
> > On Wed, Mar 03, 2021 at 06:38:16PM +0100, Christophe Leroy wrote:
> > > Le 03/03/2021 à 18:28, Will Deacon a écrit :
> > > > On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
> > > > > This code provides architectures with a way to build command line
> > > > > based on what is built in the kernel and what is handed over by the
> > > > > bootloader, based on selected compile-time options.
> > > > >
> > > > > Signed-off-by: Christophe Leroy
> > > > > ---
> > > > >include/linux/cmdline.h | 62
> > > > > +
> > > > >1 file changed, 62 insertions(+)
> > > > >create mode 100644 include/linux/cmdline.h
> > > > >
> > > > > diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
> > > > > new file mode 100644
> > > > > index ..ae3610bb0ee2
> > > > > --- /dev/null
> > > > > +++ b/include/linux/cmdline.h
> > > > > @@ -0,0 +1,62 @@
> > > > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > > > +#ifndef _LINUX_CMDLINE_H
> > > > > +#define _LINUX_CMDLINE_H
> > > > > +
> > > > > +static __always_inline size_t cmdline_strlen(const char *s)
> > > > > +{
> > > > > + const char *sc;
> > > > > +
> > > > > + for (sc = s; *sc != '\0'; ++sc)
> > > > > + ; /* nothing */
> > > > > + return sc - s;
> > > > > +}
> > > > > +
> > > > > +static __always_inline size_t cmdline_strlcat(char *dest, const char
> > > > > *src, size_t count)
> > > > > +{
> > > > > + size_t dsize = cmdline_strlen(dest);
> > > > > + size_t len = cmdline_strlen(src);
> > > > > + size_t res = dsize + len;
> > > > > +
> > > > > + /* This would be a bug */
> > > > > + if (dsize >= count)
> > > > > + return count;
> > > > > +
> > > > > + dest += dsize;
> > > > > + count -= dsize;
> > > > > + if (len >= count)
> > > > > + len = count - 1;
> > > > > + memcpy(dest, src, len);
> > > > > + dest[len] = 0;
> > > > > + return res;
> > > > > +}
> > > >
> > > > Why are these needed instead of using strlen and strlcat directly?
> > >
> > > Because on powerpc (at least), it will be used in prom_init, it is very
> > > early in the boot and KASAN shadow memory is not set up yet so calling
> > > generic string functions would crash the board.
> >
> > Hmm. We deliberately setup a _really_ early shadow on arm64 for this, can
> > you not do something similar? Failing that, I think it would be better to
> > offer the option for an arch to implement cmdline_*, but have then point to
> > the normal library routines by default.
>
> I don't think it is possible to setup an earlier early shadow.
>
> At the point we are in prom_init, the code is not yet relocated at the
> address it was linked for, and it is running with the MMU set by the
> bootloader, I can't imagine being able to setup MMU entries for the early
> shadow KASAN yet without breaking everything.
That's very similar to us; we're not relocated, although we are at least
in control of the MMU (which is using a temporary set of page-tables).
> Is it really worth trying to point to the normal library routines by default
> ? It is really only a few lines of code hence only not many bytes, and
> anyway they are in __init section so they get discarded at the end.
I would prefer to use the normal routines by default and allow architectures
to override them based on their needs, otherwise we'll end up trying to
maintain a "lowest-common-dominator" set of string routines that can be
safely run in whatever different constraints different architectures have.
Will
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
Le 03/03/2021 à 18:46, Will Deacon a écrit :
On Wed, Mar 03, 2021 at 06:38:16PM +0100, Christophe Leroy wrote:
Le 03/03/2021 à 18:28, Will Deacon a écrit :
On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
This code provides architectures with a way to build command line
based on what is built in the kernel and what is handed over by the
bootloader, based on selected compile-time options.
Signed-off-by: Christophe Leroy
---
include/linux/cmdline.h | 62 +
1 file changed, 62 insertions(+)
create mode 100644 include/linux/cmdline.h
diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
new file mode 100644
index ..ae3610bb0ee2
--- /dev/null
+++ b/include/linux/cmdline.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CMDLINE_H
+#define _LINUX_CMDLINE_H
+
+static __always_inline size_t cmdline_strlen(const char *s)
+{
+ const char *sc;
+
+ for (sc = s; *sc != '\0'; ++sc)
+ ; /* nothing */
+ return sc - s;
+}
+
+static __always_inline size_t cmdline_strlcat(char *dest, const char *src,
size_t count)
+{
+ size_t dsize = cmdline_strlen(dest);
+ size_t len = cmdline_strlen(src);
+ size_t res = dsize + len;
+
+ /* This would be a bug */
+ if (dsize >= count)
+ return count;
+
+ dest += dsize;
+ count -= dsize;
+ if (len >= count)
+ len = count - 1;
+ memcpy(dest, src, len);
+ dest[len] = 0;
+ return res;
+}
Why are these needed instead of using strlen and strlcat directly?
Because on powerpc (at least), it will be used in prom_init, it is very
early in the boot and KASAN shadow memory is not set up yet so calling
generic string functions would crash the board.
Hmm. We deliberately setup a _really_ early shadow on arm64 for this, can
you not do something similar? Failing that, I think it would be better to
offer the option for an arch to implement cmdline_*, but have then point to
the normal library routines by default.
I don't think it is possible to setup an earlier early shadow.
At the point we are in prom_init, the code is not yet relocated at the address it was linked for,
and it is running with the MMU set by the bootloader, I can't imagine being able to setup MMU
entries for the early shadow KASAN yet without breaking everything.
Is it really worth trying to point to the normal library routines by default ? It is really only a
few lines of code hence only not many bytes, and anyway they are in __init section so they get
discarded at the end.
+/*
+ * This function will append a builtin command line to the command
+ * line provided by the bootloader. Kconfig options can be used to alter
+ * the behavior of this builtin command line.
+ * @dest: The destination of the final appended/prepended string.
+ * @src: The starting string or NULL if there isn't one. Must not equal dest.
+ * @length: the length of dest buffer.
+ */
+static __always_inline void cmdline_build(char *dest, const char *src, size_t
length)
+{
+ if (length <= 0)
+ return;
+
+ dest[0] = 0;
+
+#ifdef CONFIG_CMDLINE
+ if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) {
+ cmdline_strlcat(dest, CONFIG_CMDLINE, length);
+ return;
+ }
+#endif
CONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't,
CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef?
Ah yes, since cbe46bd4f510 ("powerpc: remove CONFIG_CMDLINE #ifdef mess") it
is feasible. I can change that now.
+ if (dest != src)
+ cmdline_strlcat(dest, src, length);
+#ifdef CONFIG_CMDLINE
+ if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1)
+ cmdline_strlcat(dest, " " CONFIG_CMDLINE, length);
+#endif
Likewise, but also I'm not sure why the sizeof() is required.
It is to avoid adding a white space at the end of the command line when
CONFIG_CMDLINE is empty. But maybe it doesn't matter ?
If CONFIG_CMDLINE is empty, I don't think you can select
CONFIG_CMDLINE_EXTEND (but even if you could, I don't think it matters).
Ok I'll simplify that when I re-spin.
Christophe
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
On Wed, Mar 03, 2021 at 06:38:16PM +0100, Christophe Leroy wrote:
> Le 03/03/2021 à 18:28, Will Deacon a écrit :
> > On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
> > > This code provides architectures with a way to build command line
> > > based on what is built in the kernel and what is handed over by the
> > > bootloader, based on selected compile-time options.
> > >
> > > Signed-off-by: Christophe Leroy
> > > ---
> > > include/linux/cmdline.h | 62 +
> > > 1 file changed, 62 insertions(+)
> > > create mode 100644 include/linux/cmdline.h
> > >
> > > diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
> > > new file mode 100644
> > > index ..ae3610bb0ee2
> > > --- /dev/null
> > > +++ b/include/linux/cmdline.h
> > > @@ -0,0 +1,62 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +#ifndef _LINUX_CMDLINE_H
> > > +#define _LINUX_CMDLINE_H
> > > +
> > > +static __always_inline size_t cmdline_strlen(const char *s)
> > > +{
> > > + const char *sc;
> > > +
> > > + for (sc = s; *sc != '\0'; ++sc)
> > > + ; /* nothing */
> > > + return sc - s;
> > > +}
> > > +
> > > +static __always_inline size_t cmdline_strlcat(char *dest, const char
> > > *src, size_t count)
> > > +{
> > > + size_t dsize = cmdline_strlen(dest);
> > > + size_t len = cmdline_strlen(src);
> > > + size_t res = dsize + len;
> > > +
> > > + /* This would be a bug */
> > > + if (dsize >= count)
> > > + return count;
> > > +
> > > + dest += dsize;
> > > + count -= dsize;
> > > + if (len >= count)
> > > + len = count - 1;
> > > + memcpy(dest, src, len);
> > > + dest[len] = 0;
> > > + return res;
> > > +}
> >
> > Why are these needed instead of using strlen and strlcat directly?
>
> Because on powerpc (at least), it will be used in prom_init, it is very
> early in the boot and KASAN shadow memory is not set up yet so calling
> generic string functions would crash the board.
Hmm. We deliberately setup a _really_ early shadow on arm64 for this, can
you not do something similar? Failing that, I think it would be better to
offer the option for an arch to implement cmdline_*, but have then point to
the normal library routines by default.
> > > +/*
> > > + * This function will append a builtin command line to the command
> > > + * line provided by the bootloader. Kconfig options can be used to alter
> > > + * the behavior of this builtin command line.
> > > + * @dest: The destination of the final appended/prepended string.
> > > + * @src: The starting string or NULL if there isn't one. Must not equal
> > > dest.
> > > + * @length: the length of dest buffer.
> > > + */
> > > +static __always_inline void cmdline_build(char *dest, const char *src,
> > > size_t length)
> > > +{
> > > + if (length <= 0)
> > > + return;
> > > +
> > > + dest[0] = 0;
> > > +
> > > +#ifdef CONFIG_CMDLINE
> > > + if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) {
> > > + cmdline_strlcat(dest, CONFIG_CMDLINE, length);
> > > + return;
> > > + }
> > > +#endif
> >
> > CONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't,
> > CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef?
>
> Ah yes, since cbe46bd4f510 ("powerpc: remove CONFIG_CMDLINE #ifdef mess") it
> is feasible. I can change that now.
>
> >
> > > + if (dest != src)
> > > + cmdline_strlcat(dest, src, length);
> > > +#ifdef CONFIG_CMDLINE
> > > + if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1)
> > > + cmdline_strlcat(dest, " " CONFIG_CMDLINE, length);
> > > +#endif
> >
> > Likewise, but also I'm not sure why the sizeof() is required.
>
> It is to avoid adding a white space at the end of the command line when
> CONFIG_CMDLINE is empty. But maybe it doesn't matter ?
If CONFIG_CMDLINE is empty, I don't think you can select
CONFIG_CMDLINE_EXTEND (but even if you could, I don't think it matters).
Will
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
Le 03/03/2021 à 18:28, Will Deacon a écrit :
On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
This code provides architectures with a way to build command line
based on what is built in the kernel and what is handed over by the
bootloader, based on selected compile-time options.
Signed-off-by: Christophe Leroy
---
include/linux/cmdline.h | 62 +
1 file changed, 62 insertions(+)
create mode 100644 include/linux/cmdline.h
diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
new file mode 100644
index ..ae3610bb0ee2
--- /dev/null
+++ b/include/linux/cmdline.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CMDLINE_H
+#define _LINUX_CMDLINE_H
+
+static __always_inline size_t cmdline_strlen(const char *s)
+{
+ const char *sc;
+
+ for (sc = s; *sc != '\0'; ++sc)
+ ; /* nothing */
+ return sc - s;
+}
+
+static __always_inline size_t cmdline_strlcat(char *dest, const char *src,
size_t count)
+{
+ size_t dsize = cmdline_strlen(dest);
+ size_t len = cmdline_strlen(src);
+ size_t res = dsize + len;
+
+ /* This would be a bug */
+ if (dsize >= count)
+ return count;
+
+ dest += dsize;
+ count -= dsize;
+ if (len >= count)
+ len = count - 1;
+ memcpy(dest, src, len);
+ dest[len] = 0;
+ return res;
+}
Why are these needed instead of using strlen and strlcat directly?
Because on powerpc (at least), it will be used in prom_init, it is very early in the boot and KASAN
shadow memory is not set up yet so calling generic string functions would crash the board.
+/*
+ * This function will append a builtin command line to the command
+ * line provided by the bootloader. Kconfig options can be used to alter
+ * the behavior of this builtin command line.
+ * @dest: The destination of the final appended/prepended string.
+ * @src: The starting string or NULL if there isn't one. Must not equal dest.
+ * @length: the length of dest buffer.
+ */
+static __always_inline void cmdline_build(char *dest, const char *src, size_t
length)
+{
+ if (length <= 0)
+ return;
+
+ dest[0] = 0;
+
+#ifdef CONFIG_CMDLINE
+ if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) {
+ cmdline_strlcat(dest, CONFIG_CMDLINE, length);
+ return;
+ }
+#endif
CONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't,
CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef?
Ah yes, since cbe46bd4f510 ("powerpc: remove CONFIG_CMDLINE #ifdef mess") it is feasible. I can
change that now.
+ if (dest != src)
+ cmdline_strlcat(dest, src, length);
+#ifdef CONFIG_CMDLINE
+ if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1)
+ cmdline_strlcat(dest, " " CONFIG_CMDLINE, length);
+#endif
Likewise, but also I'm not sure why the sizeof() is required.
It is to avoid adding a white space at the end of the command line when CONFIG_CMDLINE is empty. But
maybe it doesn't matter ?
Christophe
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
> This code provides architectures with a way to build command line
> based on what is built in the kernel and what is handed over by the
> bootloader, based on selected compile-time options.
>
> Signed-off-by: Christophe Leroy
> ---
> include/linux/cmdline.h | 62 +
> 1 file changed, 62 insertions(+)
> create mode 100644 include/linux/cmdline.h
Sorry, spotted a couple of other things...
> +/*
> + * This function will append a builtin command line to the command
> + * line provided by the bootloader. Kconfig options can be used to alter
> + * the behavior of this builtin command line.
> + * @dest: The destination of the final appended/prepended string.
> + * @src: The starting string or NULL if there isn't one. Must not equal dest.
> + * @length: the length of dest buffer.
> + */
> +static __always_inline void cmdline_build(char *dest, const char *src,
> size_t length)
> +{
> + if (length <= 0)
> + return;
length is unsigned
> +
> + dest[0] = 0;
> +
> +#ifdef CONFIG_CMDLINE
> + if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) {
> + cmdline_strlcat(dest, CONFIG_CMDLINE, length);
> + return;
> + }
> +#endif
> + if (dest != src)
The kernel-doc says that @src "Must not equal dest".
Will
Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
On Tue, Mar 02, 2021 at 05:25:17PM +, Christophe Leroy wrote:
> This code provides architectures with a way to build command line
> based on what is built in the kernel and what is handed over by the
> bootloader, based on selected compile-time options.
>
> Signed-off-by: Christophe Leroy
> ---
> include/linux/cmdline.h | 62 +
> 1 file changed, 62 insertions(+)
> create mode 100644 include/linux/cmdline.h
>
> diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
> new file mode 100644
> index ..ae3610bb0ee2
> --- /dev/null
> +++ b/include/linux/cmdline.h
> @@ -0,0 +1,62 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LINUX_CMDLINE_H
> +#define _LINUX_CMDLINE_H
> +
> +static __always_inline size_t cmdline_strlen(const char *s)
> +{
> + const char *sc;
> +
> + for (sc = s; *sc != '\0'; ++sc)
> + ; /* nothing */
> + return sc - s;
> +}
> +
> +static __always_inline size_t cmdline_strlcat(char *dest, const char *src,
> size_t count)
> +{
> + size_t dsize = cmdline_strlen(dest);
> + size_t len = cmdline_strlen(src);
> + size_t res = dsize + len;
> +
> + /* This would be a bug */
> + if (dsize >= count)
> + return count;
> +
> + dest += dsize;
> + count -= dsize;
> + if (len >= count)
> + len = count - 1;
> + memcpy(dest, src, len);
> + dest[len] = 0;
> + return res;
> +}
Why are these needed instead of using strlen and strlcat directly?
> +/*
> + * This function will append a builtin command line to the command
> + * line provided by the bootloader. Kconfig options can be used to alter
> + * the behavior of this builtin command line.
> + * @dest: The destination of the final appended/prepended string.
> + * @src: The starting string or NULL if there isn't one. Must not equal dest.
> + * @length: the length of dest buffer.
> + */
> +static __always_inline void cmdline_build(char *dest, const char *src,
> size_t length)
> +{
> + if (length <= 0)
> + return;
> +
> + dest[0] = 0;
> +
> +#ifdef CONFIG_CMDLINE
> + if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) {
> + cmdline_strlcat(dest, CONFIG_CMDLINE, length);
> + return;
> + }
> +#endif
CONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't,
CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef?
> + if (dest != src)
> + cmdline_strlcat(dest, src, length);
> +#ifdef CONFIG_CMDLINE
> + if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1)
> + cmdline_strlcat(dest, " " CONFIG_CMDLINE, length);
> +#endif
Likewise, but also I'm not sure why the sizeof() is required.
Will
[PATCH v2 1/7] cmdline: Add generic function to build command line.
This code provides architectures with a way to build command line
based on what is built in the kernel and what is handed over by the
bootloader, based on selected compile-time options.
Signed-off-by: Christophe Leroy
---
include/linux/cmdline.h | 62 +
1 file changed, 62 insertions(+)
create mode 100644 include/linux/cmdline.h
diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
new file mode 100644
index ..ae3610bb0ee2
--- /dev/null
+++ b/include/linux/cmdline.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CMDLINE_H
+#define _LINUX_CMDLINE_H
+
+static __always_inline size_t cmdline_strlen(const char *s)
+{
+ const char *sc;
+
+ for (sc = s; *sc != '\0'; ++sc)
+ ; /* nothing */
+ return sc - s;
+}
+
+static __always_inline size_t cmdline_strlcat(char *dest, const char *src,
size_t count)
+{
+ size_t dsize = cmdline_strlen(dest);
+ size_t len = cmdline_strlen(src);
+ size_t res = dsize + len;
+
+ /* This would be a bug */
+ if (dsize >= count)
+ return count;
+
+ dest += dsize;
+ count -= dsize;
+ if (len >= count)
+ len = count - 1;
+ memcpy(dest, src, len);
+ dest[len] = 0;
+ return res;
+}
+
+/*
+ * This function will append a builtin command line to the command
+ * line provided by the bootloader. Kconfig options can be used to alter
+ * the behavior of this builtin command line.
+ * @dest: The destination of the final appended/prepended string.
+ * @src: The starting string or NULL if there isn't one. Must not equal dest.
+ * @length: the length of dest buffer.
+ */
+static __always_inline void cmdline_build(char *dest, const char *src, size_t
length)
+{
+ if (length <= 0)
+ return;
+
+ dest[0] = 0;
+
+#ifdef CONFIG_CMDLINE
+ if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) {
+ cmdline_strlcat(dest, CONFIG_CMDLINE, length);
+ return;
+ }
+#endif
+ if (dest != src)
+ cmdline_strlcat(dest, src, length);
+#ifdef CONFIG_CMDLINE
+ if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1)
+ cmdline_strlcat(dest, " " CONFIG_CMDLINE, length);
+#endif
+}
+
+#endif /* _LINUX_CMDLINE_H */
--
2.25.0
