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SubjectRe: [PATCH 21/23] arm64: ilp32: introduce ilp32-specific handlers for sigframe and ucontext
From
Date
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@huawei.com>
>> 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@huawei.com>
>> ---
>> 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
>>
>>

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