Re: [uClinux-dev] [PATCH] NOMMU: use copy_*_user_page() in access_process_vm()
Jie Zhang wrote:
> On 11/25/2009 02:16 PM, Jamie Lokier wrote:
> >Mike Frysinger wrote:
> >>From: Jie Zhang
> >>
> >>The mmu code uses the copy_*_user_page() variants in access_process_vm()
> >>rather than copy_*_user() as the former includes an icache flush. This is
> >>important when doing things like setting software breakpoints with gdb.
> >>So switch the nommu code over to do the same.
> >
> >Reasonable, but it's a bit subtle don't you think?
> >How about a one-line comment saying why it's using copy_*_user_page()?
> >
> >(If it was called copy_*_user_flush_icache() I wouldn't say anything,
> >but it isn't).
> >
> But I think it's well known in Linux kernel developers that
> copy_to_user_page and copy_from_user_page should do cache flushing. It's
> documented in Documentation/cachetlb.txt. I don't think it's necessary
> to replicate it here.
You're right, however I now think the commit message is misleading.
Since this is the *only place in the entire kernel* where these
functions are used (plus the mmu equivalent), I'm not sure I'd agree
about well known, and the name could be better (copy_*_user_ptrace()),
but I agree now, it doesn't need a comment.
It was the talk of icache flush which bothered me, as I (wrongly)
assumed copy_*_user_page() was used elsewhere, without knowledge of
icache vs non-icache differences - which are often the responsibility
of userspace to get right, so often the kernel does not care.
In fact, it's not just icache. copy_*_user_page() has to do some
*data* cache flushing too, on some architecures. For example, see
arch/sparc/include/asm/cacheflush_64.h:
#define copy_to_user_page(vma, page, vaddr, dst, src, len) \
do {\
flush_cache_page(vma, vaddr, page_to_pfn(page));\
memcpy(dst, src, len); \
flush_ptrace_access(vma, page, vaddr, src, len, 0); \
} while (0)
#define copy_from_user_page(vma, page, vaddr, dst, src, len)\
do {\
flush_cache_page(vma, vaddr, page_to_pfn(page));\
memcpy(dst, src, len); \
flush_ptrace_access(vma, page, vaddr, dst, len, 1); \
} while (0)
I'm not sure why I don't see the same dcache flushing on ARM, so I
wonder if the ARM implementation of these buggy.
Anyway, that means the commit message is a little misleading, saying
it's for the icache flush. It is for whatever icache and dcache
flushes are needed for a ptrace access.
Which is why, given they are only used for ptrace (have just grepped),
I'm inclined to think it'd be clearer to rename the functions to
copy_*_user_ptrace(). And make your no-mmu change of course :-)
Any thoughts on the rename?
-- Jamie
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Re: [uClinux-dev] [PATCH] NOMMU: use copy_*_user_page() in access_process_vm()
On Wed, Nov 25, 2009 at 06:49, Jamie Lokier wrote:
> Jie Zhang wrote:
>> On 11/25/2009 02:16 PM, Jamie Lokier wrote:
>> >Mike Frysinger wrote:
>> >>From: Jie Zhang
>> >>
>> >>The mmu code uses the copy_*_user_page() variants in access_process_vm()
>> >>rather than copy_*_user() as the former includes an icache flush. This is
>> >>important when doing things like setting software breakpoints with gdb.
>> >>So switch the nommu code over to do the same.
>> >
>> >Reasonable, but it's a bit subtle don't you think?
>> >How about a one-line comment saying why it's using copy_*_user_page()?
>> >
>> >(If it was called copy_*_user_flush_icache() I wouldn't say anything,
>> >but it isn't).
>> >
>> But I think it's well known in Linux kernel developers that
>> copy_to_user_page and copy_from_user_page should do cache flushing. It's
>> documented in Documentation/cachetlb.txt. I don't think it's necessary
>> to replicate it here.
>
> You're right, however I now think the commit message is misleading.
>
> Since this is the *only place in the entire kernel* where these
> functions are used (plus the mmu equivalent), I'm not sure I'd agree
> about well known, and the name could be better (copy_*_user_ptrace()),
> but I agree now, it doesn't need a comment.
>
> It was the talk of icache flush which bothered me, as I (wrongly)
> assumed copy_*_user_page() was used elsewhere, without knowledge of
> icache vs non-icache differences - which are often the responsibility
> of userspace to get right, so often the kernel does not care.
>
> In fact, it's not just icache. copy_*_user_page() has to do some
> *data* cache flushing too, on some architecures. For example, see
> arch/sparc/include/asm/cacheflush_64.h:
>
> #define copy_to_user_page(vma, page, vaddr, dst, src, len) \
> do { \
> flush_cache_page(vma, vaddr, page_to_pfn(page)); \
> memcpy(dst, src, len); \
> flush_ptrace_access(vma, page, vaddr, src, len, 0); \
> } while (0)
>
> #define copy_from_user_page(vma, page, vaddr, dst, src, len) \
> do { \
> flush_cache_page(vma, vaddr, page_to_pfn(page)); \
> memcpy(dst, src, len); \
> flush_ptrace_access(vma, page, vaddr, dst, len, 1); \
> } while (0)
>
> I'm not sure why I don't see the same dcache flushing on ARM, so I
> wonder if the ARM implementation of these buggy.
>
> Anyway, that means the commit message is a little misleading, saying
> it's for the icache flush. It is for whatever icache and dcache
> flushes are needed for a ptrace access.
>
> Which is why, given they are only used for ptrace (have just grepped),
> I'm inclined to think it'd be clearer to rename the functions to
> copy_*_user_ptrace(). And make your no-mmu change of course :-)
> Any thoughts on the rename?
these are all good points, but i think unrelated to the patch in
question ;). they can be done as a follow up.
-mike
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RE: [uClinux-dev] Controlling GPIO on coldfire
> Hi Dan, > > Dan Snyder wrote: > > I am attempting to use the hardware encryption support provided by the 5271 > > and am running into this problem. (Access Error Exception when attempting > > to read/write from userspace). How can I modify the kernel to allow access > > to 0x4000 through 0x401b009f ? > > Section 11.4 of the 5271 RM seems to be what you are looking for. > It describes the access control implemented on this part. > > > > I have been poking through the kernel headers for hours now and I am still > > clueless. > > You probably won't find anything associated with this in the headers, > since the kernel doesn't generally support any of these types of > features. > > > > I believe I need to add the address range to > > /arch/m68knommu/platform/527x/config.c but I am not sure if this is correct > > or exactly how to do so. > > config.c would be an ok place to set this. I suspect you want > to add something like: > > writeb(0x04, 0x4030) > > which sets the GPACR0 register to allows kernel and user > modes to have read/write access. > > > > Any guidance would be much appreciated. Thank you > > Regards > Greg Thank you Greg, this worked perfectly. The reference manual had confused me by its suggestion to use the MOVEC instruction to set these registers. - Dan ___ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
[uClinux-dev] Re: [PATCH] NOMMU: use copy_*_user_page() in access_process_vm()
Mike Frysinger wrote:
From: Jie Zhang
The mmu code uses the copy_*_user_page() variants in access_process_vm()
rather than copy_*_user() as the former includes an icache flush. This is
important when doing things like setting software breakpoints with gdb.
So switch the nommu code over to do the same.
Signed-off-by: Jie Zhang
Signed-off-by: Mike Frysinger
Acked-by: Greg Ungerer
mm/nommu.c |6 --
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/nommu.c b/mm/nommu.c
index 9876fa0..51ae9be 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1889,9 +1889,11 @@ int access_process_vm(struct task_struct *tsk, unsigned
long addr, void *buf, in
/* only read or write mappings where it is permitted */
if (write && vma->vm_flags & VM_MAYWRITE)
- len -= copy_to_user((void *) addr, buf, len);
+ copy_to_user_page(vma, NULL, NULL,
+ (void *) addr, buf, len);
else if (!write && vma->vm_flags & VM_MAYREAD)
- len -= copy_from_user(buf, (void *) addr, len);
+ copy_from_user_page(vma, NULL, NULL,
+ buf, (void *) addr, len);
else
len = 0;
} else {
--
Greg Ungerer -- Principal EngineerEMAIL: g...@snapgear.com
SnapGear Group, McAfee PHONE: +61 7 3435 2888
8 Gardner Close FAX: +61 7 3217 5323
Milton, QLD, 4064, AustraliaWEB: http://www.SnapGear.com
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Re: [uClinux-dev] problem with compilation uclinux-dist
Hi, thiago wrote: Hi i have a problem, i'm can't compile uclinux-dist because an error ocurred i386-linux-gcc: libgcc.a: No such file or directory make[3]: ** [lib/ld-uClibc.so] Erro 1 make[3]: Saindo do diretório `$PROJECT/uClinux-dist/uClibc' make[2]: ** [uClibc] Erro 2 make[2]: Saindo do diretório `$PROJECT/uClinux-dist/lib' make[1]: ** [all] Erro 2 make[1]: Saindo do diretório `$PROJECT/uClinux-dist/lib' make: ** [subdirs] Erro 1 help-me please Can you post more information please? What version of the uClinux-dist? What toolchain are you using? What target are you building for? What kernel version did you select? I assume you choose uClibc? Regards Greg -- Greg Ungerer -- Principal EngineerEMAIL: g...@snapgear.com SnapGear Group, McAfee PHONE: +61 7 3435 2888 8 Gardner Close FAX: +61 7 3217 5323 Milton, QLD, 4064, AustraliaWEB: http://www.SnapGear.com ___ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
Re: [uClinux-dev] Problem:Spurious Interrupt on Coldfire................
Hi Vinod, Vinod Nagare wrote: I am using a custom build board using MCF5485 and uClinux 2.4.x ported on it. I am using General Purpose Timer (GPT), which is generating interrupts to CPU and an ISR is connected to this interrupt. When the timer is configured to generate interrupt for period 100ms the ISR is invoked every 100ms and functions properly. But when I configurs timer (GPT) to generate interrupt every 10ms following message is printed on console (connected to minicom) and the system starves and ISR is not invoked. Spurious interrupt 4488788 Spurious interrupt 4289755 .. and such messages are printed continously. Please help me to solve this problem as I need an ISR to be executed every 2ms. Can you show us the code? Regards Greg Greg Ungerer -- Principal EngineerEMAIL: g...@snapgear.com SnapGear Group, McAfee PHONE: +61 7 3435 2888 8 Gardner Close FAX: +61 7 3217 5323 Milton, QLD, 4064, AustraliaWEB: http://www.SnapGear.com ___ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
