Re: [tcf-dev] Errors from get_regs_PC are not handled

["Ragnerstam, Andreas" <andreas.ragnerstam@xxxxxxxxx>]

Hi, Eugene,

 

I noticed that my change lead to other problems when doing other symbol lookups.

My problem was that the behavior on Linux and Windows was different. Because during the Windows lookup I have two readers, one for ELF and one for PE. Even though I am reading an ELF file it enters the PE reader, then that fails because it cannot read memory. So I wanted the same behavior on Linux as on Windows. But you can probably ignore this, I will work around it in another way.

 

Thanks,

Andreas

 

From: tcf-dev-bounces@xxxxxxxxxxx [mailto:tcf-dev-bounces@xxxxxxxxxxx] On Behalf Of Eugene Tarassov
Sent: Thursday, November 3, 2016 7:20 PM
To: TCF Development <tcf-dev@xxxxxxxxxxx>
Subject: Re: [tcf-dev] Errors from get_regs_PC are not handled

 

Hi Andreas,

 

In some cases, we do want PC access error to be ignored. Planting a breakpoint would be one example – address of a sane breakpoint should be same regardless of current PC.

 

I cannot tell if such change would cause a regression. Why exactly this is a problem?

 

Regards,

Eugene

 

From: tcf-dev-bounces@xxxxxxxxxxx [mailto:tcf-dev-bounces@xxxxxxxxxxx] On Behalf Of Ragnerstam, Andreas
Sent: Thursday, November 03, 2016 5:49 AM
To: 'tcf-dev@xxxxxxxxxxx'
Subject: [tcf-dev] Errors from get_regs_PC are not handled

 

Hi,

 

I  have run into a case when get_regs_PC goes wrong, but the get_sym_context in symbols_elf.c does not notice this error so code keeps on running. The problem I run into is running this function (which calls context_read_reg) with a context that is not active. This will make get_regs_PC return 0 with errno set to ERR_NOT_ACTIVE. After running a while errno will be cleared and this error will never be discovered.

 

The following patch for symbols_elf.c would solve my problem:

         }

         sym_ip = get_regs_PC(ctx);

+        if (errno != 0)

+                return -1;

         if (cache_miss_count() > cnt) {

             /* The value of the PC (0) is incorrect. */

 

But I see that everywhere get_regs_PC is used there is no error check. Is this intentional? Is this function supposed to always work correctly?

 

Thanks,

Andreas

 

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