Messages in this thread Patch in this message |  | | Date | Fri, 7 Feb 2003 19:50:58 +0000 | From | Russell King <> | Subject | Re: [PATCH] Restore module support. |
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On Fri, Feb 07, 2003 at 10:43:19AM -0800, Luck, Tony wrote: > > (2) has the disadvantage that its touching non-architecture specific > > code, but this is the option I'd prefer due to the obvious performance > > advantage. However, I'm afraid that it isn't worth the effort to fix > > up vmalloc and /proc/kcore. vmalloc fix appears simple, but /proc/kcore > > has issues (anyone know what KCORE_BASE is all about?) > > KCORE_BASE is my fault ... it was an attempt to fix the "modules > below PAGE_OFFSET" problem for the ia64 port. For a few nanoseconds > the code just here looked like this: > > #if VMALLOC_START < PAGE_OFFSET > #define KCORE_BASE VMALLOC_START > #else > #define KCORE_BASE PAGE_OFFSET > #endif
Ah, ok. What I'm thinking of is something like the following (untested and probably improperly thought out patch...):
--- orig/fs/proc/kcore.c Sat Nov 2 18:58:18 2002 +++ linux/fs/proc/kcore.c Fri Feb 7 19:48:35 2003 @@ -99,7 +99,10 @@ } #else /* CONFIG_KCORE_AOUT */ +#ifndef KCORE_BASE #define KCORE_BASE PAGE_OFFSET +#define in_vmlist_region(x) ((x) >= VMALLOC_START && (x) < VMALLOC_END) +#endif #define roundup(x, y) ((((x)+((y)-1))/(y))*(y)) @@ -394,7 +397,7 @@ tsz = buflen; while (buflen) { - if ((start >= VMALLOC_START) && (start < VMALLOC_END)) { + if (in_vmlist_region(start)) { char * elf_buf; struct vm_struct *m; unsigned long curstart = start; An architecture could then define KCORE_BASE and in_vmlist_region() alongside their VMALLOC_START definition if they needed to change them.
> There was some discussion on a better way to do this, by adding the > kernel itself to the vmlist, and eliminating all the special case code. > I took a brief look at this, but realised that there were all sorts > of ugly race conditions with /proc/kcore if a module is loaded/unloaded > after some process has read the Elf header.
Well, only root can debug using /proc/kcore, and I'd suggest the best answer to that problem is "if it hurts, don't do that." I don't think you should prevent modules from being unloaded just because you have /proc/kcore open.
-- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html
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