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Message-ID: <20210309214051.GS109100@zorba>
Date: Tue, 9 Mar 2021 13:40:51 -0800
From: Daniel Walker <danielwa@...co.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Will Deacon <will@...nel.org>, Rob Herring <robh@...nel.org>,
Daniel Gimpelevich <daniel@...pelevich.san-francisco.ca.us>,
Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
xe-linux-external@...co.com, Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Ruslan Ruslichenko <rruslich@...co.com>,
Ruslan Bilovol <rbilovol@...co.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] CMDLINE: powerpc: convert to generic builtin
command line
On Tue, Mar 09, 2021 at 08:56:47AM +0100, Christophe Leroy wrote:
>
>
> Le 09/03/2021 à 01:02, Daniel Walker a écrit :
> > This updates the powerpc code to use the CONFIG_GENERIC_CMDLINE
> > option.
> >
> > Cc: xe-linux-external@...co.com
> > Signed-off-by: Ruslan Ruslichenko <rruslich@...co.com>
> > Signed-off-by: Ruslan Bilovol <rbilovol@...co.com>
> > Signed-off-by: Daniel Walker <danielwa@...co.com>
> > ---
> > arch/powerpc/Kconfig | 37 +--------------------------------
> > arch/powerpc/kernel/prom.c | 1 +
> > arch/powerpc/kernel/prom_init.c | 35 ++++++++++++++++++-------------
> > 3 files changed, 23 insertions(+), 50 deletions(-)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 107bb4319e0e..276b06d5c961 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -167,6 +167,7 @@ config PPC
> > select EDAC_SUPPORT
> > select GENERIC_ATOMIC64 if PPC32
> > select GENERIC_CLOCKEVENTS_BROADCAST if SMP
> > + select GENERIC_CMDLINE
> > select GENERIC_CMOS_UPDATE
> > select GENERIC_CPU_AUTOPROBE
> > select GENERIC_CPU_VULNERABILITIES if PPC_BARRIER_NOSPEC
> > @@ -906,42 +907,6 @@ config PPC_DENORMALISATION
> > Add support for handling denormalisation of single precision
> > values. Useful for bare metal only. If unsure say Y here.
> > -config CMDLINE
> > - string "Initial kernel command string"
> > - default ""
> > - help
> > - On some platforms, there is currently no way for the boot loader to
> > - pass arguments to the kernel. For these platforms, you can supply
> > - some command-line options at build time by entering them here. In
> > - most cases you will need to specify the root device here.
> > -
> > -choice
> > - prompt "Kernel command line type" if CMDLINE != ""
> > - default CMDLINE_FROM_BOOTLOADER
> > -
> > -config CMDLINE_FROM_BOOTLOADER
> > - bool "Use bootloader kernel arguments if available"
> > - help
> > - Uses the command-line options passed by the boot loader. If
> > - the boot loader doesn't provide any, the default kernel command
> > - string provided in CMDLINE will be used.
> > -
> > -config CMDLINE_EXTEND
> > - bool "Extend bootloader kernel arguments"
> > - help
> > - The command-line arguments provided by the boot loader will be
> > - appended to the default kernel command string.
> > -
> > -config CMDLINE_FORCE
> > - bool "Always use the default kernel command string"
> > - help
> > - Always use the default kernel command string, even if the boot
> > - loader passes other arguments to the kernel.
> > - This is useful if you cannot or don't want to change the
> > - command-line options your boot loader passes to the kernel.
> > -
> > -endchoice
> > -
> > config EXTRA_TARGETS
> > string "Additional default image types"
> > help
> > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> > index ae3c41730367..96d0a01be1b4 100644
> > --- a/arch/powerpc/kernel/prom.c
> > +++ b/arch/powerpc/kernel/prom.c
> > @@ -27,6 +27,7 @@
> > #include <linux/irq.h>
> > #include <linux/memblock.h>
> > #include <linux/of.h>
> > +#include <linux/cmdline.h>
>
> Why is this needed in prom.c ?
Must have been a mistake, I don't think it's needed.
> > #include <linux/of_fdt.h>
> > #include <linux/libfdt.h>
> > #include <linux/cpu.h>
> > diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> > index e9d4eb6144e1..657241534d69 100644
> > --- a/arch/powerpc/kernel/prom_init.c
> > +++ b/arch/powerpc/kernel/prom_init.c
> > @@ -27,6 +27,7 @@
> > #include <linux/initrd.h>
> > #include <linux/bitops.h>
> > #include <linux/pgtable.h>
> > +#include <linux/cmdline.h>
> > #include <asm/prom.h>
> > #include <asm/rtas.h>
> > #include <asm/page.h>
> > @@ -242,15 +243,6 @@ static int __init prom_strcmp(const char *cs, const char *ct)
> > return 0;
> > }
> > -static char __init *prom_strcpy(char *dest, const char *src)
> > -{
> > - char *tmp = dest;
> > -
> > - while ((*dest++ = *src++) != '\0')
> > - /* nothing */;
> > - return tmp;
> > -}
> > -
>
> This game with prom_strcpy() should go a separate preceeding patch.
>
> Also, it looks like checkpatch.pl recommends to use strscpy() instead of strlcpy().
strscpy() is very large. I'm not sure it's compatible with this prom_init.c
environment.
> > static int __init prom_strncmp(const char *cs, const char *ct, size_t count)
> > {
> > unsigned char c1, c2;
> > @@ -276,6 +268,20 @@ static size_t __init prom_strlen(const char *s)
> > return sc - s;
> > }
> > +static size_t __init prom_strlcpy(char *dest, const char *src, size_t size)
> > +{
> > + size_t ret = prom_strlen(src);
> > +
> > + if (size) {
> > + size_t len = (ret >= size) ? size - 1 : ret;
> > +
> > + memcpy(dest, src, len);
> > + dest[len] = '\0';
> > + }
> > + return ret;
> > +}
> > +
> > +
> > static int __init prom_memcmp(const void *cs, const void *ct, size_t count)
> > {
> > const unsigned char *su1, *su2;
> > @@ -304,6 +310,7 @@ static char __init *prom_strstr(const char *s1, const char *s2)
> > return NULL;
> > }
> > +#ifdef GENERIC_CMDLINE_NEED_STRLCAT
> > static size_t __init prom_strlcat(char *dest, const char *src, size_t count)
> > {
> > size_t dsize = prom_strlen(dest);
> > @@ -323,6 +330,7 @@ static size_t __init prom_strlcat(char *dest, const char *src, size_t count)
> > return res;
> > }
> > +#endif
> > #ifdef CONFIG_PPC_PSERIES
> > static int __init prom_strtobool(const char *s, bool *res)
> > @@ -775,12 +783,11 @@ static void __init early_cmdline_parse(void)
> > prom_cmd_line[0] = 0;
> > p = prom_cmd_line;
> > - if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && (long)prom.chosen > 0)
> > + if ((long)prom.chosen > 0)
> > l = prom_getprop(prom.chosen, "bootargs", p, COMMAND_LINE_SIZE-1);
> > - if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) || l <= 0 || p[0] == '\0')
> > - prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
> > - sizeof(prom_cmd_line));
> > + cmdline_add_builtin_custom(prom_cmd_line, (l > 0 ? p : NULL), sizeof(prom_cmd_line),
> > + __prombss, prom_strlcpy, prom_strlcat);
>
> So we are referencing a function that doesn't exist (namely prom_strlcat).
> But it works because cmdline_add_builtin_custom() looks like a function but
> is in fact an obscure macro that doesn't use prom_strlcat() unless
> GENERIC_CMDLINE_NEED_STRLCAT is defined.
>
> IMHO that's awful for readability and code maintenance.
powerpc is a special case, there's no other users like this. The reason is
because of all the difficulty in this prom_init.c code. A lot of the generic
code has similar kind of changes to work across architectures.
> > prom_printf("command line: %s\n", prom_cmd_line);
> > @@ -2706,7 +2713,7 @@ static void __init flatten_device_tree(void)
> > /* Add "phandle" in there, we'll need it */
> > namep = make_room(&mem_start, &mem_end, 16, 1);
> > - prom_strcpy(namep, "phandle");
> > + prom_strlcpy(namep, "phandle", 8);
>
> Should be in a separate patch.
I can move it, I missed that from the first round.
Daniel
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