Re: [PATCH 02/11] x86/lib/cpio.c: Find cpio data by its file name
On Sat, 18 Aug 2012, Fenghua Yu wrote: > Given a file's name, find its starting point in a cpio formated area. This > will > be used to find microcode in combined initrd image. But this function is > generic and could be used in other places. Shouldn't this (very useful) feature get its own documentation in Documentation/ ? -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH 02/11] x86/lib/cpio.c: Find cpio data by its file name
> -Original Message- > From: Henrique de Moraes Holschuh [mailto:h...@hmh.eng.br] > Sent: Saturday, August 18, 2012 3:13 PM > To: Yu, Fenghua > Cc: H Peter Anvin; Ingo Molnar; Thomas Gleixner; Mallick, Asit K; > Tigran Aivazian; Andreas Herrmann; Borislav Petkov; linux-kernel; x86 > Subject: Re: [PATCH 02/11] x86/lib/cpio.c: Find cpio data by its file > name > > On Sat, 18 Aug 2012, Fenghua Yu wrote: > > Given a file's name, find its starting point in a cpio formated area. > This will > > be used to find microcode in combined initrd image. But this function > is > > generic and could be used in other places. > > Shouldn't this (very useful) feature get its own documentation in > Documentation/ ? Yes, I can document the feature. And if it's generic and useful, this function could be put in generic kernel instead of in x86 arch. Thanks. -Fenghua -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 02/11] x86/lib/cpio.c: Find cpio data by its file name
On Sat, 18 Aug 2012, Yu, Fenghua wrote: > > From: Henrique de Moraes Holschuh [mailto:h...@hmh.eng.br] On Sat, 18 Aug > > 2012, Fenghua Yu wrote: > > > Given a file's name, find its starting point in a cpio formated area. > > This will > > > be used to find microcode in combined initrd image. But this function > > is > > > generic and could be used in other places. > > > > Shouldn't this (very useful) feature get its own documentation in > > Documentation/ ? > > Yes, I can document the feature. And if it's generic and useful, this > function could be put in generic kernel instead of in x86 arch. It is useful to override/fix all sort of critical firmware-provided tables, for example. ACPI table overrides should use this new cpio-based scheme as well, and I recall someone wrote something about device tree overrides in a past thread... -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 02/11] x86/lib/cpio.c: Find cpio data by its file name
On 08/18/2012 09:35 PM, Henrique de Moraes Holschuh wrote: > On Sat, 18 Aug 2012, Yu, Fenghua wrote: >>> From: Henrique de Moraes Holschuh [mailto:h...@hmh.eng.br] On Sat, 18 Aug >>> 2012, Fenghua Yu wrote: Given a file's name, find its starting point in a cpio formated area. >>> This will be used to find microcode in combined initrd image. But this function >>> is generic and could be used in other places. >>> >>> Shouldn't this (very useful) feature get its own documentation in >>> Documentation/ ? >> >> Yes, I can document the feature. And if it's generic and useful, this >> function could be put in generic kernel instead of in x86 arch. > > It is useful to override/fix all sort of critical firmware-provided tables, > for example. ACPI table overrides should use this new cpio-based scheme as > well, and I recall someone wrote something about device tree overrides in a > past thread... > Indeed, we already have those two users already identified. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 02/11] x86/lib/cpio.c: Find cpio data by its file name
On Sat, Aug 18, 2012 at 01:15:20AM -0700, Fenghua Yu wrote:
> From: Fenghua Yu
>
> Given a file's name, find its starting point in a cpio formated area. This
> will
s/file's/file/ cpio-formatted
> be used to find microcode in combined initrd image. But this function is
> generic and could be used in other places.
>
> Signed-off-by: Fenghua Yu
> ---
> arch/x86/include/asm/cpio.h | 10 +++
> arch/x86/lib/Makefile |2 +
> arch/x86/lib/cpio.c | 179
> +++
> 3 files changed, 191 insertions(+), 0 deletions(-)
> create mode 100644 arch/x86/include/asm/cpio.h
> create mode 100644 arch/x86/lib/cpio.c
>
> diff --git a/arch/x86/include/asm/cpio.h b/arch/x86/include/asm/cpio.h
> new file mode 100644
> index 000..26a4333
> --- /dev/null
> +++ b/arch/x86/include/asm/cpio.h
> @@ -0,0 +1,10 @@
> +#include
> +#include
> +
> +struct cpio_data {
> + void *data;
> + unsigned long size;
> +};
> +
> +extern struct cpio_data
> +find_cpio_data(const char *name, const void *data, size_t len);
> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
> index b00f678..452a4b5 100644
> --- a/arch/x86/lib/Makefile
> +++ b/arch/x86/lib/Makefile
> @@ -45,3 +45,5 @@ else
> lib-y += copy_user_64.o copy_user_nocache_64.o
> lib-y += cmpxchg16b_emu.o
> endif
> +
> +obj-y += cpio.o
> diff --git a/arch/x86/lib/cpio.c b/arch/x86/lib/cpio.c
> new file mode 100644
> index 000..70ac474
> --- /dev/null
> +++ b/arch/x86/lib/cpio.c
> @@ -0,0 +1,179 @@
> +/*
> + * findcpio.c
> + *
> + * Find a specific cpio member; must precede any compressed content.
> + *
> + * Copyright (C) 2012 H Peter Anvin"
stray "
> + * Fenghua Yu
> + */
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
Why all those includes?
> +#include
> +
> +enum cpio_fields {
> + C_MAGIC,
> + C_INO,
> + C_MODE,
> + C_UID,
> + C_GID,
> + C_NLINK,
> + C_MTIME,
> + C_FILESIZE,
> + C_MAJ,
> + C_MIN,
> + C_RMAJ,
> + C_RMIN,
> + C_NAMESIZE,
> + C_CHKSUM,
> + C_NFIELDS
> +};
> +
> +#if defined(__i386__) || defined(__x86_64__)
> +static size_t cpio_strlen(const char *name)
> +{
> + size_t n = -1;
> +
> + asm("repne; scasb"
> + : "+D" (name), "+c" (n)
> + : "a" (0));
> +
> + return -2 - n;
> +}
> +
> +static int cpio_memcmp(const void *p1, const void *p2, size_t n)
> +{
> + unsigned char rv;
> +
> + asm("repe; cmpsb; setne %0"
> + : "=r" (rv), "+S" (p1), "+D" (p2), "+c" (n));
> +
> + return rv;
> +}
I guess those are speed optimizations on x86, right? In any
case, can we reuse some of the already present ones like
memcmp in and strlen in
...
> +#else
> +static size_t cpio_strlen(const char *name)
> +{
> + size_t n = 0;
> +
> + while (*name++)
> + n++;
> +
> + return n;
> +}
> +
> +static int cpio_memcmp(const void *p1, const void *p2, size_t n)
> +{
> + const unsigned char *u1 = p1;
> + const unsigned char *u2 = p2;
> + int d;
> +
> + while (n--) {
> + d = *u2++ - *u1++;
> + if (d)
> + return d;
> + }
> + return 0;
> +}
> +#endif
and, similarly the generic ones in lib/string.c?
> +
> +#define ALIGN4(p) ((void *)(((size_t)p + 3) & ~3))
> +
> +struct cpio_data find_cpio_data(const char *name, const void *data, size_t
> len)
> +{
> + const size_t cpio_header_len = 8*C_NFIELDS - 2;
> + struct cpio_data cd = { NULL, 0 };
> + const char *p, *dptr, *nptr;
> + unsigned int ch[C_NFIELDS], *chp, v;
> + unsigned char c, x;
> + size_t mynamesize = cpio_strlen(name) + 1;
> + int i, j;
> +
> + p = data;
> +
> + while (len > cpio_header_len) {
> + if (!*p) {
> + /* All cpio headers need to be 4-byte aligned */
> + p += 4;
> + len -= 4;
> + continue;
> + }
> +
> + j = 6; /* The magic field is only 6 characters */
Maybe put all comments above the line they refer to, like above instead
of them trailing?
> + chp = ch;
> + for (i = C_NFIELDS; i; i--) {
> + v = 0;
> + while (j--) {
> + v <<= 4;
> + c = *p++;
> +
> + x = c - '0';
> + if (x < 10) {
> + v += x;
> + continu
