[PATCH] NOMMU: Add '[stack]' label to /proc/pid/maps output
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From: Mike Frysinger on 1 Jun 2010 17:00 On Tue, Jun 1, 2010 at 15:07, Linus Torvalds wrote: > On Tue, 1 Jun 2010, David Howells wrote: >> Add support to the NOMMU /proc/pid/maps file to show which mapping is the stack >> of the original thread after execve. This is largely based on the MMU code. > > Umm? The MMU code that we _reverted_? to be fair, this patch was written a few kernel revisions ago and you're referring to commit merged a few weeks ago ... > It turns out to be totally useless, since people put stacks in various > different places, and the values the kernel does see end up not even being > the "real" stack top. > > See commit 34441427aab4bdb3069a4ffcda69a99357abcb2e. > > Just don't do it. but i dont think we're talking the same thing. that commit refers to [threadstack]. afaict, [stack] is still in there. -mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Mike Frysinger on 4 Jun 2010 19:10
On Fri, Jun 4, 2010 at 16:48, Andrew Morton wrote: > On Tue, 01 Jun 2010 19:59:37 +0100 David Howells wrote: >> From: Mike Frysinger <vapier(a)gentoo.org> >> >> Add support to the NOMMU /proc/pid/maps file to show which mapping is the stack >> of the original thread after execve. This is largely based on the MMU code. >> Subsidiary thread stacks are not indicated. >> >> For FDPIC, we now get: >> >> root:/> cat /proc/self/maps >> 02064000-02067ccc rw-p 0004d000 00:01 22 /bin/busybox >> 0206e000-0206f35c rw-p 00006000 00:01 295 /lib/ld-uClibc.so.0 >> 025f0000-025f6f0c r-xs 00000000 00:01 295 /lib/ld-uClibc.so.0 >> 02680000-026ba6b0 r-xs 00000000 00:01 297 /lib/libc.so.0 >> 02700000-0274d384 r-xs 00000000 00:01 22 /bin/busybox >> 02816000-02817000 rw-p 00000000 00:00 0 >> 02848000-0284c0d8 rw-p 00000000 00:00 0 >> 02860000-02880000 rw-p 00000000 00:00 0 [stack] >> >> The semi-downside here is that for FLAT, we get: >> >> root:/> cat /proc/155/maps >> 029f0000-029f9000 rwxp 00000000 00:00 0 [stack] >> >> The reason being that FLAT combines a whole lot of stuff into one map >> (including the stack). But this isn't any worse than the current output (which >> is nothing), so screw it. > > So it's a non-back-compatible change which can a) break nommu-only > userspace and b) unbreak mmu-tested userspace which gets run on nommu. i dont see how it breaks anything really. any code that parses the maps file has to account for an optional label in the maps output. i guess if someone wrote some code that does something special with "[stack]", then behavior would change with FLAT files, but that's pretty unlikely i would think. plus, FLAT is not ELF and as such, its layout in memory is highly unlike any existing ELF layout. so someone would already have to be writing a custom handler for FLAT files which means they account for the "one blob is everything" layout. -mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |