From: Jurij Smakov <jurij@wooyd.org>
To: sparclinux@vger.kernel.org
Subject: Re: longjmp question
Date: Sat, 08 Oct 2011 12:55:35 +0000 [thread overview]
Message-ID: <20111008125534.GA5065@wooyd.org> (raw)
In-Reply-To: <20111007232209.GA11892@wooyd.org>
On Sat, Oct 08, 2011 at 02:43:55AM -0400, David Miller wrote:
> From: Jurij Smakov <jurij@wooyd.org>
> Date: Sat, 8 Oct 2011 00:22:10 +0100
>
> > #define RW_FP [%fp + 0x48]
>
> Let's just do away with this value entirely and do this the
> safest way possible, since this is the slow path:
>
> diff --git a/sysdeps/sparc/sparc32/__longjmp.S b/sysdeps/sparc/sparc32/__longjmp.S
> index a5453b4..70e8e29 100644
> --- a/sysdeps/sparc/sparc32/__longjmp.S
> +++ b/sysdeps/sparc/sparc32/__longjmp.S
> @@ -22,7 +22,6 @@
> #include <jmpbuf-offsets.h>
> #define ENV(base,reg) [%base + (reg * 4)]
> #define ST_FLUSH_WINDOWS 3
> -#define RW_FP [%fp + 0x48]
>
> ENTRY(__longjmp)
> /* Store our arguments in global registers so we can still
> @@ -55,6 +54,7 @@ LOC(loop):
> ld ENV(g1,JB_SP), %o0 /* Delay slot: extract target SP. */
>
> LOC(thread):
> + save %sp, -96, %sp
> /*
> * Do a "flush register windows trap". The trap handler in the
> * kernel writes all the register windows to their stack slots, and
> @@ -67,15 +67,13 @@ LOC(thread):
> #ifdef PTR_DEMANGLE
> ld ENV(g1,JB_PC), %g5 /* Set return PC. */
> ld ENV(g1,JB_SP), %g1 /* Set saved SP on restore below. */
> - PTR_DEMANGLE2 (%o7, %g5, %g4)
> + PTR_DEMANGLE2 (%i7, %g5, %g4)
> PTR_DEMANGLE2 (%fp, %g1, %g4)
> #else
> - ld ENV(g1,JB_PC), %o7 /* Set return PC. */
> + ld ENV(g1,JB_PC), %i7 /* Set return PC. */
> ld ENV(g1,JB_SP), %fp /* Set saved SP on restore below. */
> #endif
> - sub %fp, 64, %sp /* Allocate a register frame. */
> - st %g3, RW_FP /* Set saved FP on restore below. */
> - retl
> + jmp %i7 + 8
> restore %g2, 0, %o0 /* Restore values from above register frame. */
I don't really see anything in the code which would ensure that after
we execute this restore, fp is going to be set to target fp value
(available as ENV(g1,JB_FP) or g3. It might be the responsibility of
the unwinding part, but then it would not explain why such code was
explicitly present in the old version.
Best regards,
--
Jurij Smakov jurij@wooyd.org
Key: http://www.wooyd.org/pgpkey/ KeyID: C99E03CC
next prev parent reply other threads:[~2011-10-08 12:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-07 23:22 longjmp question Jurij Smakov
2011-10-07 23:42 ` David Miller
2011-10-08 6:43 ` David Miller
2011-10-08 12:55 ` Jurij Smakov [this message]
2011-10-08 19:22 ` David Miller
2011-10-12 21:22 ` Jurij Smakov
2011-10-12 22:09 ` David Miller
2011-10-12 22:17 ` David Miller
2011-10-12 23:06 ` David Miller
2011-10-12 23:21 ` Jurij Smakov
2011-10-12 23:42 ` David Miller
2011-10-13 22:06 ` Jurij Smakov
2011-10-13 22:35 ` David Miller
2011-10-14 23:06 ` Jurij Smakov
2011-10-14 23:26 ` David Miller
2011-10-16 17:07 ` Jurij Smakov
2011-10-17 0:56 ` David Miller
2011-10-18 20:46 ` Jurij Smakov
2011-10-18 20:53 ` David Miller
2011-10-22 9:00 ` Jurij Smakov
2011-10-22 9:05 ` David Miller
2011-10-22 9:43 ` Jurij Smakov
2011-10-22 22:54 ` David Miller
2011-10-23 13:47 ` Jurij Smakov
2011-10-23 20:35 ` David Miller
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