* John Johansen <[email protected]>: > On 11/26/25 07:12, Helge Deller wrote: > > * david laight <[email protected]>: > > > On Wed, 26 Nov 2025 12:03:03 +0100 > > > Helge Deller <[email protected]> wrote: > > > > > > > On 11/26/25 11:44, david laight wrote: > > > ... > > > > > > diff --git a/security/apparmor/match.c b/security/apparmor/match.c > > > > > > index 26e82ba879d44..3dcc342337aca 100644 > > > > > > --- a/security/apparmor/match.c > > > > > > +++ b/security/apparmor/match.c > > > > > > @@ -71,10 +71,10 @@ static struct table_header *unpack_table(char > > > > > > *blob, size_t bsize) > > > > > > u8, u8, byte_to_byte); > > > > > > > > > > Is that that just memcpy() ? > > > > > > > > No, it's memcpy() only on big-endian machines. > > > > > > You've misread the quoting... > > > The 'data8' case that was only half there is a memcpy(). > > > > > > > On little-endian machines it converts from big-endian > > > > 16/32-bit ints to little-endian 16/32-bit ints. > > > > > > > > But I see some potential for optimization here: > > > > a) on big-endian machines just use memcpy() > > > > > > true > > > > > > > b) on little-endian machines use memcpy() to copy from > > > > possibly-unaligned > > > > memory to then known-to-be-aligned destination. Then use a loop > > > > with > > > > be32_to_cpu() instead of get_unaligned_xx() as it's faster. > > > > > > There is a function that does a loop byteswap of a buffer - no reason > > > to re-invent it. > > > > I assumed there must be something, but I did not see it. Which one? > > > > > But I doubt it is always (if ever) faster to do a copy and then byteswap. > > > The loop control and extra memory accesses kill performance. > > > > Yes, you are probably right. > > > > > Not that I've seen a fast get_unaligned() - I don't think gcc or clang > > > generate optimal code - For LE I think it is something like: > > > low = *(addr & ~3); > > > high = *((addr + 3) & ~3); > > > shift = (addr & 3) * 8; > > > value = low << shift | high >> (32 - shift); > > > Note that it is only 2 aligned memory reads - even for 64bit. > > > > Ok, then maybe we should keep it simple like this patch: > > > > [PATCH v2] apparmor: Optimize table creation from possibly unaligned memory > > > > Source blob may come from userspace and might be unaligned. > > Try to optize the copying process by avoiding unaligned memory accesses. > > > > Signed-off-by: Helge Deller <[email protected]> > > > > diff --git a/security/apparmor/include/match.h > > b/security/apparmor/include/match.h > > index 1fbe82f5021b..386da2023d50 100644 > > --- a/security/apparmor/include/match.h > > +++ b/security/apparmor/include/match.h > > @@ -104,16 +104,20 @@ struct aa_dfa { > > struct table_header *tables[YYTD_ID_TSIZE]; > > }; > > -#define byte_to_byte(X) (X) > > +#define byte_to_byte(X) (*(X)) > > #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX) \ > > do { \ > > typeof(LEN) __i; \ > > TTYPE *__t = (TTYPE *) TABLE; \ > > BTYPE *__b = (BTYPE *) BLOB; \ > > - for (__i = 0; __i < LEN; __i++) { \ > > - __t[__i] = NTOHX(__b[__i]); \ > > - } \ > > + BUILD_BUG_ON(sizeof(TTYPE) != sizeof(BTYPE)); \ > > + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) || sizeof(BTYPE) == 1) \ > > + memcpy(__t, __b, (LEN) * sizeof(BTYPE)); \ > > + else /* copy & convert convert from big-endian */ \ > > + for (__i = 0; __i < LEN; __i++) { \ > > + __t[__i] = NTOHX(&__b[__i]); \ > > + } \ > > } while (0) > > static inline size_t table_size(size_t len, size_t el_size) > > diff --git a/security/apparmor/match.c b/security/apparmor/match.c > > index c5a91600842a..13e2f6873329 100644 > > --- a/security/apparmor/match.c > > +++ b/security/apparmor/match.c > > @@ -15,6 +15,7 @@ > > #include <linux/vmalloc.h> > > #include <linux/err.h> > > #include <linux/kref.h> > > +#include <linux/unaligned.h> > > #include "include/lib.h" > > #include "include/match.h" > > @@ -70,10 +71,10 @@ static struct table_header *unpack_table(char *blob, > > size_t bsize) > > u8, u8, byte_to_byte); > > else if (th.td_flags == YYTD_DATA16) > > UNPACK_ARRAY(table->td_data, blob, th.td_lolen, > > - u16, __be16, be16_to_cpu); > > + u16, __be16, get_unaligned_be16); > > else if (th.td_flags == YYTD_DATA32) > > UNPACK_ARRAY(table->td_data, blob, th.td_lolen, > > - u32, __be32, be32_to_cpu); > > + u32, __be32, get_unaligned_be32); > > else > > goto fail; > > /* if table was vmalloced make sure the page tables are synced > > I think we can make one more tweak, in just not using UNPACK_ARRAY at all for > the byte case > ie. > > diff --git a/security/apparmor/match.c b/security/apparmor/match.c > index 26e82ba879d44..389202560675c 100644 > --- a/security/apparmor/match.c > +++ b/security/apparmor/match.c > @@ -67,8 +67,7 @@ static struct table_header *unpack_table(char *blob, size_t > bsize) > table->td_flags = th.td_flags; > table->td_lolen = th.td_lolen; > if (th.td_flags == YYTD_DATA8) > - UNPACK_ARRAY(table->td_data, blob, th.td_lolen, > - u8, u8, byte_to_byte); > + memcp(table->td_data, blob, th.td_lolen);
True. Then byte_to_byte() can go away in match.h as well. So, here is a (untested) v3: [PATCH v3] apparmor: Optimize table creation from possibly unaligned memory Source blob may come from userspace and might be unaligned. Try to optize the copying process by avoiding unaligned memory accesses. Signed-off-by: Helge Deller <[email protected]> diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h index 1fbe82f5021b..19e72b3e8f49 100644 --- a/security/apparmor/include/match.h +++ b/security/apparmor/include/match.h @@ -104,16 +104,18 @@ struct aa_dfa { struct table_header *tables[YYTD_ID_TSIZE]; }; -#define byte_to_byte(X) (X) - #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX) \ do { \ typeof(LEN) __i; \ TTYPE *__t = (TTYPE *) TABLE; \ BTYPE *__b = (BTYPE *) BLOB; \ - for (__i = 0; __i < LEN; __i++) { \ - __t[__i] = NTOHX(__b[__i]); \ - } \ + BUILD_BUG_ON(sizeof(TTYPE) != sizeof(BTYPE)); \ + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) \ + memcpy(__t, __b, (LEN) * sizeof(BTYPE)); \ + else /* copy & convert convert from big-endian */ \ + for (__i = 0; __i < LEN; __i++) { \ + __t[__i] = NTOHX(&__b[__i]); \ + } \ } while (0) static inline size_t table_size(size_t len, size_t el_size) diff --git a/security/apparmor/match.c b/security/apparmor/match.c index c5a91600842a..1e32c8ba14ae 100644 --- a/security/apparmor/match.c +++ b/security/apparmor/match.c @@ -15,6 +15,7 @@ #include <linux/vmalloc.h> #include <linux/err.h> #include <linux/kref.h> +#include <linux/unaligned.h> #include "include/lib.h" #include "include/match.h" @@ -66,14 +67,13 @@ static struct table_header *unpack_table(char *blob, size_t bsize) table->td_flags = th.td_flags; table->td_lolen = th.td_lolen; if (th.td_flags == YYTD_DATA8) - UNPACK_ARRAY(table->td_data, blob, th.td_lolen, - u8, u8, byte_to_byte); + memcpy(table->td_data, blob, th.td_lolen); else if (th.td_flags == YYTD_DATA16) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, - u16, __be16, be16_to_cpu); + u16, __be16, get_unaligned_be16); else if (th.td_flags == YYTD_DATA32) UNPACK_ARRAY(table->td_data, blob, th.td_lolen, - u32, __be32, be32_to_cpu); + u32, __be32, get_unaligned_be32); else goto fail; /* if table was vmalloced make sure the page tables are synced
