[U-Boot] [PATCH] Do not copy to same address
In some cases (e.g. bootm with a elf payload) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisser weisserm@arcor.de --- lib/string.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/lib/string.c b/lib/string.c index b375b81..b8a9203 100644 --- a/lib/string.c +++ b/lib/string.c @@ -445,6 +445,9 @@ char * bcopy(const char * src, char * dest, int count) { char *tmp = dest;
+ if (src == dest) + return dest; + while (count--) *tmp++ = *src++;
@@ -467,6 +470,9 @@ void * memcpy(void *dest, const void *src, size_t count) unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src; char *d8, *s8;
+ if (src == dest) + return dest; + /* while all data is aligned (common case), copy a word at a time */ if ( (((ulong)dest | (ulong)src) & (sizeof(*dl) - 1)) == 0) { while (count >= sizeof(*dl)) { @@ -497,6 +503,9 @@ void * memmove(void * dest,const void *src,size_t count) { char *tmp, *s;
+ if (src == dest) + return dest; + if (dest <= src) { tmp = (char *) dest; s = (char *) src;
this summary is kind of weak. please prefix it with something like "string:" or "memcpy/memmove:". keep in mind that the summary needs to quickly pick out what the changeset is doing from every other changeset in the tree based only on that. or at least give a pretty good idea.
side note, i wonder why we even bother with bcopy at all. i dont see any users of it in the tree ... -mike
Am 12.04.2011 09:05, schrieb Mike Frysinger:
this summary is kind of weak. please prefix it with something like "string:" or "memcpy/memmove:". keep in mind that the summary needs to quickly pick out what the changeset is doing from every other changeset in the tree based only on that. or at least give a pretty good idea.
OK. I will wait for additional comments and post a V2 then.
side note, i wonder why we even bother with bcopy at all. i dont see any users of it in the tree ...
I see the same. But removal of bcopy should be a separate patch.
Regards, Matthias
Hi Matthias,
Le 12/04/2011 08:58, Matthias Weisser a écrit :
In some cases (e.g. bootm with a elf payload) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisserweisserm@arcor.de
lib/string.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
I believe that is a V2 patch, right? Please tag it as V2 in the subject line, and add patch history below the commit message delimiter ('---' ).
Amicalement,
Am 12.04.2011 09:06, schrieb Albert ARIBAUD:
Hi Matthias,
Le 12/04/2011 08:58, Matthias Weisser a écrit :
In some cases (e.g. bootm with a elf payload) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisserweisserm@arcor.de
lib/string.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
I believe that is a V2 patch, right? Please tag it as V2 in the subject line, and add patch history below the commit message delimiter ('---' ).
No, it is a replacement for http://patchwork.ozlabs.org/patch/79447/ which picks up a suggestion from Wolfgang.
Regards, Matthias
Hi Matthias,
Le 12/04/2011 09:13, Matthias Weißer a écrit :
Am 12.04.2011 09:06, schrieb Albert ARIBAUD:
Hi Matthias,
Le 12/04/2011 08:58, Matthias Weisser a écrit :
In some cases (e.g. bootm with a elf payload) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisserweisserm@arcor.de
lib/string.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
I believe that is a V2 patch, right? Please tag it as V2 in the subject line, and add patch history below the commit message delimiter ('---' ).
No, it is a replacement for http://patchwork.ozlabs.org/patch/79447/ which picks up a suggestion from Wolfgang.
So it is a V3, not V2, but still you must tag it so that readers who see the previous patch can relate it to the 'replacement' -- yes, even if the files touched by V2 are different.
Regards, Matthias
Amicalement,
Am 12.04.2011 09:27, schrieb Albert ARIBAUD:
Hi Matthias,
Le 12/04/2011 09:13, Matthias Weißer a écrit :
Am 12.04.2011 09:06, schrieb Albert ARIBAUD:
Hi Matthias,
Le 12/04/2011 08:58, Matthias Weisser a écrit :
In some cases (e.g. bootm with a elf payload) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisserweisserm@arcor.de
lib/string.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
I believe that is a V2 patch, right? Please tag it as V2 in the subject line, and add patch history below the commit message delimiter ('---' ).
No, it is a replacement for http://patchwork.ozlabs.org/patch/79447/ which picks up a suggestion from Wolfgang.
So it is a V3, not V2, but still you must tag it so that readers who see the previous patch can relate it to the 'replacement' -- yes, even if the files touched by V2 are different.
Well, as the patch is only slightly related to my original one I thought it is better to start a new patch as I had to change the subject also. The only relation between them would be the reference in the mail header. Maybe Wolfgang can bring some light into this situation.
What would be the right way to post this patch? And what would be the right way to post a patch doing exactly the same to the ARM optimized version of memcpy?
Sorry for all that administrative questions.
Regards, Matthias
Hi Matthias,
Le 12/04/2011 09:49, Matthias Weißer a écrit :
Well, as the patch is only slightly related to my original one I thought it is better to start a new patch as I had to change the subject also. The only relation between them would be the reference in the mail header. Maybe Wolfgang can bring some light into this situation.
What would be the right way to post this patch?
Never mind with the previous patch, then; but please keep history of this one (maybe including a patchwork URL pointing to the previous patch with the other name) and tag its V2 in the subject line.
And what would be the right way to post a patch doing exactly the same to the ARM optimized version of memcpy?
Simply submit a separate patch.
Regards, Matthias
Amicalement,
In some cases (e.g. bootm with a elf payload which is already at the right position) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisser weisserm@arcor.de --- Changes since V1: - Made subject more informative - Removed the optimization from bcopy as bcopy is not used anywhere
lib/string.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/lib/string.c b/lib/string.c index b375b81..2c4f0ec 100644 --- a/lib/string.c +++ b/lib/string.c @@ -467,6 +467,9 @@ void * memcpy(void *dest, const void *src, size_t count) unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src; char *d8, *s8;
+ if (src == dest) + return dest; + /* while all data is aligned (common case), copy a word at a time */ if ( (((ulong)dest | (ulong)src) & (sizeof(*dl) - 1)) == 0) { while (count >= sizeof(*dl)) { @@ -497,6 +500,9 @@ void * memmove(void * dest,const void *src,size_t count) { char *tmp, *s;
+ if (src == dest) + return dest; + if (dest <= src) { tmp = (char *) dest; s = (char *) src;
Hello,
Am 23.05.2011 11:03, schrieb Matthias Weisser:
In some cases (e.g. bootm with a elf payload which is already at the right position) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisserweisserm@arcor.de
Changes since V1:
- Made subject more informative
- Removed the optimization from bcopy as bcopy is not used anywhere
lib/string.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/lib/string.c b/lib/string.c index b375b81..2c4f0ec 100644 --- a/lib/string.c +++ b/lib/string.c @@ -467,6 +467,9 @@ void * memcpy(void *dest, const void *src, size_t count) unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src; char *d8, *s8;
- if (src == dest)
return dest;
here is the same, as in the patch I've commented before. There exist no reason to add a check for identity to memcpy() because memcpy doesn't support overlapping regions (and identity is just a special case of overlapping regions). If something might call memcpy() with overlapping or identical regions, it should use memmove().
/* while all data is aligned (common case), copy a word at a time */ if ( (((ulong)dest | (ulong)src)& (sizeof(*dl) - 1)) == 0) { while (count>= sizeof(*dl)) { @@ -497,6 +500,9 @@ void * memmove(void * dest,const void *src,size_t count) { char *tmp, *s;
- if (src == dest)
return dest;- if (dest<= src) {
Here it is ok, but the check <= could be modified to < too.
Just to clarify my reasoning: the only reason why memcpy() exists, is because it should have been a faster version of memmove() without the necessary checks. So if a bug proof of version of memcpy() is wanted, there is no need to have a different implementation for memcpy() and memcpy() could just be an alias for memmove(). But adding a check for identity to memcpy() is unnecessary.
Sorry, but I had to comment this after having read to many comments in a bug about something similiar in
https://bugzilla.redhat.com/show_bug.cgi?id=638477
(Be aware, reading that bug might hurt your brain)
Regards,
Alexander
Dear Alexander Holler,
In message 4DDACC8B.6090507@ahsoftware.de you wrote:
--- a/lib/string.c +++ b/lib/string.c @@ -467,6 +467,9 @@ void * memcpy(void *dest, const void *src, size_t count) unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src; char *d8, *s8;
- if (src == dest)
return dest;here is the same, as in the patch I've commented before. There exist no reason to add a check for identity to memcpy() because memcpy doesn't support overlapping regions (and identity is just a special case of overlapping regions). If something might call memcpy() with overlapping or identical regions, it should use memmove().
In an ideal world, nobody will ever use any interfces in a non-compliant or incorrect way.
In reality, all kind of errors happen. A little defensive programming like the one above helps a lot, so please stop complaining even if you think you don't need this.
Thanks.
Wolfgang Denk
Am 23.05.2011 23:55, schrieb Wolfgang Denk:
Dear Alexander Holler,
In message4DDACC8B.6090507@ahsoftware.de you wrote:
--- a/lib/string.c +++ b/lib/string.c @@ -467,6 +467,9 @@ void * memcpy(void *dest, const void *src, size_t count) unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src; char *d8, *s8;
- if (src == dest)
return dest;here is the same, as in the patch I've commented before. There exist no reason to add a check for identity to memcpy() because memcpy doesn't support overlapping regions (and identity is just a special case of overlapping regions). If something might call memcpy() with overlapping or identical regions, it should use memmove().
In an ideal world, nobody will ever use any interfces in a non-compliant or incorrect way.
In reality, all kind of errors happen. A little defensive programming like the one above helps a lot, so please stop complaining even if you think you don't need this.
So you I will look forward to checks for NULL pointers and similiar in all C standard functions implemented in u-boot to circumvent tons of possible real world bugs in all callers of strcpy, strlen, mem* and whatever.
Reads promising,
regards,
Alexander
Dear Alexander Holler,
In message 4DDADBB6.30607@ahsoftware.de you wrote:
So you I will look forward to checks for NULL pointers and similiar in all C standard functions implemented in u-boot to circumvent tons of possible real world bugs in all callers of strcpy, strlen, mem* and whatever.
If you think a bit about this, you may find it more difficult than you expect. Keep in mind that on most systems supported by U-Boot code like
int *p = (int *)0;
print("*p = %d\n", *p);
is perfectly legal and supposed to work without any problems - because 0 is a legal address, and it makes perfect senze that commands like "md" or "cp" can be used to access it. In the result, strcpy(), strlen(), mem*() and whatever must beable to work on address 0 likeon any other address, too.
:-P
Best regards,
Wolfgang Denk
Am 24.05.2011 00:22, schrieb Wolfgang Denk:
Dear Alexander Holler,
In message4DDADBB6.30607@ahsoftware.de you wrote:
So you I will look forward to checks for NULL pointers and similiar in all C standard functions implemented in u-boot to circumvent tons of possible real world bugs in all callers of strcpy, strlen, mem* and whatever.
If you think a bit about this, you may find it more difficult than you expect. Keep in mind that on most systems supported by U-Boot code like
int *p = (int *)0;
print("*p = %d\n", *p);
is perfectly legal and supposed to work without any problems - because 0 is a legal address, and it makes perfect senze that commands like "md" or "cp" can be used to access it. In the result, strcpy(), strlen(), mem*() and whatever must beable to work on address 0 likeon any other address, too.
:-P
I've never seen a valid use of strcpy() with a null-pointer in real world programs, which we are talking about, except in bugs.
BTW, you missed to quote my suggestion to get rid of the implementation of memcpy() and use always memmove(). That would be really defensive programming and if the unnecessary identity-check in memcpy isn't of interest, the additional other check done by memmove() shouldn't be a problem too.
But I will stop complaining as requested and getting silent again.
Regards,
Alexander
On Monday, May 23, 2011 18:38:49 Alexander Holler wrote:
Am 24.05.2011 00:22, schrieb Wolfgang Denk:
Alexander Holler wrote:
So you I will look forward to checks for NULL pointers and similiar in all C standard functions implemented in u-boot to circumvent tons of possible real world bugs in all callers of strcpy, strlen, mem* and whatever.
If you think a bit about this, you may find it more difficult than you expect. Keep in mind that on most systems supported by U-Boot code like
int *p = (int *)0;
print("*p = %d\n", *p);
is perfectly legal and supposed to work without any problems - because 0 is a legal address, and it makes perfect senze that commands like "md" or "cp" can be used to access it. In the result, strcpy(), strlen(), mem*() and whatever must beable to work on address 0 likeon any other address, too.
I've never seen a valid use of strcpy() with a null-pointer in real world programs, which we are talking about, except in bugs.
i'm lazy and type "0" all the time for loading files, copying memory, displaying things, etc... in u-boot. i dont feel like retraining my finger muscle memory if i dont have to ;). -mike
Am 24.05.2011 05:47, schrieb Mike Frysinger:
I've never seen a valid use of strcpy() with a null-pointer in real world programs, which we are talking about, except in bugs.
i'm lazy and type "0" all the time for loading files, copying memory, displaying things, etc... in u-boot. i dont feel like retraining my finger muscle memory if i dont have to ;). -mike
Using a 4 should be better for your finger.
Alexander
On Tue, 24 May 2011 00:22:49 +0200 Wolfgang Denk wd@denx.de wrote:
Dear Alexander Holler,
In message 4DDADBB6.30607@ahsoftware.de you wrote:
So you I will look forward to checks for NULL pointers and similiar in all C standard functions implemented in u-boot to circumvent tons of possible real world bugs in all callers of strcpy, strlen, mem* and whatever.
If you think a bit about this, you may find it more difficult than you expect. Keep in mind that on most systems supported by U-Boot code like
int *p = (int *)0;
print("*p = %d\n", *p);
is perfectly legal and supposed to work without any problems -
Might want to pass -fno-delete-null-pointer-checks...
As for memcpy/memmove, if in U-Boot it's to be legal to pass overlapping regions to memcpy(), why have separate implementations (not to mention bcopy...)?
-Scott
Dear Scott Wood,
In message 20110524143749.0b508c66@schlenkerla.am.freescale.net you wrote:
Might want to pass -fno-delete-null-pointer-checks...
Thanks for pointing out.
As for memcpy/memmove, if in U-Boot it's to be legal to pass overlapping regions to memcpy(), why have separate implementations (not to mention bcopy...)?
Define "legal"? Legal as in "everything that is not explicitly forbidden"? Legal as in "any code that does not exwecute the HCF instruction"?
The man page says: "The memory areas should not overlap. Use memmove(3) if the memory areas do overlap." I have nothing to add here.
As for the different implementations: well, U-Boot imported tons of code from different sources, using different interfaces and library functions. Where needed, the missing library functions got added.
Cleanup patches are always welcome.
Best regards,
Wolfgang Denk
Hello Wolfgang
Am 23.05.2011 11:03, schrieb Matthias Weisser:
In some cases (e.g. bootm with a elf payload which is already at the right position) there is a in place copy of data to the same address. Catching this saves some ms while booting.
What about this patch? As the initial submission of the patch was inside the merge window (see http://patchwork.ozlabs.org/patch/90725/) I would like to see the current version of this patch (see http://patchwork.ozlabs.org/patch/96841/) in the upcoming release.
Sorry for the broken reference in patchwork. I try my best next time.
If the community decides to NACK the patch I would be happy if you could accept http://patchwork.ozlabs.org/patch/79325/
Thanks Matthias
Am 14.06.2011 08:18, schrieb Matthias Weißer:
Hello Wolfgang
Am 23.05.2011 11:03, schrieb Matthias Weisser:
In some cases (e.g. bootm with a elf payload which is already at the right position) there is a in place copy of data to the same address. Catching this saves some ms while booting.
What about this patch? As the initial submission of the patch was inside the merge window (see http://patchwork.ozlabs.org/patch/90725/) I would like to see the current version of this patch (see http://patchwork.ozlabs.org/patch/96841/) in the upcoming release.
Sorry for the broken reference in patchwork. I try my best next time.
If the community decides to NACK the patch I would be happy if you could accept http://patchwork.ozlabs.org/patch/79325/
Ping?
Thanks Matthias
Dear Wolfgang
Am 14.06.2011 08:18, schrieb Matthias Weißer:
Am 23.05.2011 11:03, schrieb Matthias Weisser:
In some cases (e.g. bootm with a elf payload which is already at the right position) there is a in place copy of data to the same address. Catching this saves some ms while booting.
What about this patch? As the initial submission of the patch was inside the merge window (see http://patchwork.ozlabs.org/patch/90725/) I would like to see the current version of this patch (see http://patchwork.ozlabs.org/patch/96841/) in the upcoming release.
May I kindly ask you if http://patchwork.ozlabs.org/patch/96841/ can go in as the merge window is now open again?
Thanks Matthias
Dear Matthias Weisser,
In message 1306141435-24001-1-git-send-email-weisserm@arcor.de you wrote:
In some cases (e.g. bootm with a elf payload which is already at the right position) there is a in place copy of data to the same address. Catching this saves some ms while booting.
Signed-off-by: Matthias Weisser weisserm@arcor.de
Changes since V1:
- Made subject more informative
- Removed the optimization from bcopy as bcopy is not used anywhere
lib/string.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
Applied, thanks.
Best regards,
Wolfgang Denk
participants (7)
-
Albert ARIBAUD -
Alexander Holler -
Matthias Weisser -
Matthias Weißer
-
Mike Frysinger -
Scott Wood -
Wolfgang Denk