Re: [PATCH 21/23] arm64: ilp32: introduce ilp32-specific handlers for sigframe and ucontext

[Zhangjian (Bamvor)]

Hi,

On 2016/6/13 1:44, Yury Norov wrote:
> Hi Bamvor,
>
> Sorry, I missed this patch.
>
> On Sat, Jun 04, 2016 at 07:34:32PM +0800, Zhangjian (Bamvor) wrote:
> > Hi,
> >
> > I found an issue of unwind with the following code. The correct backtrace
> > should be:
> > (gdb) where
> > #0 0x004004d0 in my_sig (sig=11) at test_force3.c:16
> > #1 <signal handler called>
> > #2 func2 (num=0) at test_force3.c:22
> > #3 0x00400540 in func1 (num=1) at test_force3.c:28
> > #4 0x00400574 in main (argc=1, argv=0xffd7bc04) at test_force3.c:33
> >
> > Without my patch, the backtrace is:
> > (gdb) where
> > #0 0x00400490 in my_sig (sig=11) at test_force3.c:16
> > #1 <signal handler called>
> > #2 0x004004e4 in main (argc=1, argv=0xffe6f8f4) at test_force3.c:33
> >
> > With my patch which fix the wrong frame pointer(setup_return calculate the offset
> > of fp through ilp32_sigframe instead of sigfreame), the backtrace is:
> > (gdb) where
> > #0 0x00400490 in my_sig (sig=11) at test_force3.c:16
> > #1 <signal handler called>
> > #2 func1 () at test_force3.c:28
> > #3 0x004004e4 in main (argc=1, argv=0xffe6f8f4) at test_force3.c:33
> >
> > I am not sure there is still some issue in kernel. But it seem that the gdb of ilp32
> > does not work correctly when unwind without framepointer.
> >
> > The test code is:
> >
> >  From 7e364a765097f57aed2d73f94c1688c2e7343e79 Mon Sep 17 00:00:00 2001
> > From: Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>
> > Date: Sat, 4 Jun 2016 14:30:05 +0800
> > Subject: [PATCH] arm64: ilp32: fix for wrong fp offset when calculate the
> >   new fp
> >
> > ILP32 define its own sigframe(ilp32_sigframe) because of the
> > difference uc_context. setup_return do not use ilp32 specific
> > sigframe to calculate the new offset of fp which lead to wrong
> > fp in signal handler. At this circumstance, gdb backtrace will miss
> > one item:
> > (gdb) where
> >
> > It should be:
> > (gdb) where
> >
> > The test code is as follows:
> >
> > void my_sig(int sig)
> > {
> >          printf("sig=%d\n", sig);
> >          *(int *)0 = 0x0;
> > }
> >
> > void func2(int num)
> > {
> >          printf("%s: %d\n", __FUNCTION__, num);
> >          *(int *)0 = 0x0;
> >          func2(num-1);
> > }
> >
> > void func1(int num)
> > {
> >          printf("%s\n", __FUNCTION__);
> >          func2(num - 1);
> > }
> >
> > int main(int argc, char **argv)
> > {
> >          signal(11, my_sig);
> >          func1(argc);
> >          return 0;
> > }
> >
> > This patch fix this by passing the correct offset of fp to
> > setup_return.
> > Test pass on both ILP32 and LP64 in aarch64 EE.
> >
> > Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>
> > ---
> >   arch/arm64/include/asm/signal_common.h | 3 ++-
> >   arch/arm64/kernel/signal.c             | 9 +++++----
> >   arch/arm64/kernel/signal_ilp32.c       | 4 ++--
> >   3 files changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/signal_common.h b/arch/arm64/include/asm/signal_common.h
> > index de93c71..a5d7b63 100644
> > --- a/arch/arm64/include/asm/signal_common.h
> > +++ b/arch/arm64/include/asm/signal_common.h
> > @@ -29,6 +29,7 @@ int setup_sigcontex(struct sigcontext __user *uc_mcontext,
> >   		    struct pt_regs *regs);
> >   int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sf);
> >   void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
> > -			void __user *frame, off_t sigframe_off, int usig);
> > +			void __user *frame, off_t sigframe_off, off_t fp_off,
> > +			int usig);
> >
> >   #endif /* __ASM_SIGNAL_COMMON_H */
> > diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
> > index 038bebe..e66a6e9 100644
> > --- a/arch/arm64/kernel/signal.c
> > +++ b/arch/arm64/kernel/signal.c
> > @@ -256,14 +256,14 @@ static struct rt_sigframe __user *get_sigframe(struct ksignal *ksig,
> >   }
> >
> >   void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
> > -			 void __user *frame, off_t sigframe_off, int usig)
> > +			 void __user *frame, off_t sigframe_off, off_t fp_off,
> > +			 int usig)
> >   {
> >   	__sigrestore_t sigtramp;
> >
> >   	regs->regs[0] = usig;
> >   	regs->sp = (unsigned long)frame;
> > -	regs->regs[29] = regs->sp + sigframe_off +
> > -		offsetof(struct sigframe, fp);
> > +	regs->regs[29] = regs->sp + sigframe_off + fp_off;
>
> I think you are right here. The only nitpick is what for we send 2
> offsets just to add one to another inside setup_return()?
> We can do like this:
>
>          void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
>          			 void __user *frame, off_t fp_off, int usig)
>          {
>          	__sigrestore_t sigtramp;
>
>          	regs->regs[0] = usig;
>          	regs->sp = (unsigned long)frame;
>          	regs->regs[29] = regs->sp + fp_off;
>                  [...]
>          }
>
> Where fp_off calculation is done by caller.
>
> 	setup_return(regs, &ksig->ka, frame,
> 		offsetof(struct rt_sigframe, sig) + offsetof(struct sigframe, fp),
>                  usig);
>
> For me it's more clear to understand what happens with this approach.
> I don't think struct rt_sigframe will grow, but we can even introduce
> some helper for it:
>          #define RT_SIGFRAME_FP_POS (offsetof(struct rt_sigframe, sig) + offsetof(struct sigframe, fp))
>
> If no objections, I'll apply your patch with my fix in next series.
Sure. Thanks.

Regards

Bamvor
> >   	regs->pc = (unsigned long)ka->sa.sa_handler;
> >
> >   	if (ka->sa.sa_flags & SA_RESTORER)
> > @@ -294,7 +294,8 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
> >   	err |= setup_sigframe(&frame->sig, regs, set);
> >   	if (err == 0) {
> >   		setup_return(regs, &ksig->ka, frame,
> > -			offsetof(struct rt_sigframe, sig), usig);
> > +			offsetof(struct rt_sigframe, sig),
> > +			offsetof(struct sigframe, fp), usig);
> >   		if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
> >   			err |= copy_siginfo_to_user(&frame->info, &ksig->info);
> >   			regs->regs[1] = (unsigned long)&frame->info;
> > diff --git a/arch/arm64/kernel/signal_ilp32.c b/arch/arm64/kernel/signal_ilp32.c
> > index a8ea73e..9030f14 100644
> > --- a/arch/arm64/kernel/signal_ilp32.c
> > +++ b/arch/arm64/kernel/signal_ilp32.c
> > @@ -147,7 +147,6 @@ static struct ilp32_rt_sigframe __user *ilp32_get_sigframe(struct ksignal *ksig,
> >   	struct ilp32_rt_sigframe __user *frame;
> >
> >   	sp = sp_top = sigsp(regs->sp, ksig);
> > -
> >   	sp = (sp - sizeof(struct ilp32_rt_sigframe)) & ~15;
> >   	frame = (struct ilp32_rt_sigframe __user *)sp;
> >
> > @@ -183,7 +182,8 @@ int ilp32_setup_rt_frame(int usig, struct ksignal *ksig,
> >   	err |= setup_ilp32_sigframe(&frame->sig, regs, set);
> >   	if (err == 0) {
> >   		setup_return(regs, &ksig->ka, frame,
> > -			     offsetof(struct ilp32_rt_sigframe, sig), usig);
> > +			     offsetof(struct ilp32_rt_sigframe, sig),
> > +			     offsetof(struct ilp32_sigframe, fp), usig);
> >   		regs->regs[1] = (unsigned long)&frame->info;
> >   		regs->regs[2] = (unsigned long)&frame->sig.uc;
> >   	}
> > --
> > 1.8.4.5
> >
> > Regards
> >
> > Bamvor