Messages in this thread Patch in this message |  | | | From | Paolo 'Blaisorblade' Giarrusso <> | | Subject | [PATCH 03/11] uml: fix signal code x86-64 [for 2.6.15] | | Date | Wed, 26 Oct 2005 00:01:18 +0200 |
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
The problems in this area came to light while fixing a compile failure with GCC 4, in commit bcb01b8a67476e6f748086e626df8424cc27036d. I went comparing this code with x86_64 frame construction (which we should ABI compatible with) and resync'ed the code a bit.
It isn't yet perfect, because we don't yet save floating point context. But that will come later.
Please give a critical eye, even because things currently have no reported misbehaviour, and this code is complex enough.
CC: Andi Kleen <ak@suse.de> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> --- arch/um/sys-x86_64/signal.c | 19 ++++++++++++++++--- 1 files changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/um/sys-x86_64/signal.c b/arch/um/sys-x86_64/signal.c --- a/arch/um/sys-x86_64/signal.c +++ b/arch/um/sys-x86_64/signal.c @@ -164,6 +164,7 @@ struct rt_sigframe #define round_down(m, n) (((m) / (n)) * (n)) +/* Taken from arch/x86_64/kernel/signal.c:setup_rt_frame(). */ int setup_signal_stack_si(unsigned long stack_top, int sig, struct k_sigaction *ka, struct pt_regs * regs, siginfo_t *info, sigset_t *set) @@ -173,9 +174,21 @@ int setup_signal_stack_si(unsigned long int err = 0; struct task_struct *me = current; - frame = (struct rt_sigframe __user *) - round_down(stack_top - sizeof(struct rt_sigframe), 16) - 8; - frame = (struct rt_sigframe *) ((unsigned long) frame - 128); + /* Leave space on the stack for the Red Zone, and for saving FP + * registers, even if this doesn't happen. We don't have a way to test + * used_math(), so we do that inconditionally. + * + * XXX: RED-PEN: currently, we're using a Red Zone also for any + * alternate stack set up by sigaltstack(), which x86-64 doesn't do + * (because there shouldn't be any code executing there). This could + * cause failures if user setup a too little alternate stack.*/ + + fp = (struct rt_sigframe *) round_down(stack_top - 128 - + sizeof(struct _fpstate), 16); + + /* Now leave the space for the rest of signal frame. */ + frame = (void __user *) round_down((unsigned long) fp - + sizeof(struct rt_sigframe), 16) - 8; if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate))) goto out; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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