[PATCH] elf: fix pldd on targets that map objects above 2^63 [BZ #34641]

[Stian Halseth]

Hi,

On Thu, 2026-09-17 at 10:33 +0200, Florian Weimer wrote:
> * Stian Halseth:
> 
> > > The process_vm_readv was not added at same time on all ABIs.
> > > Although
> > > for mostly kABI it was done on 3.2, for arm32 compat (aarch64
> > > kernel)
> > > it was done on 3.7, on hppa at 3.9.
> > > 
> > > Maybe we can just lseek/read:
> > > 
> > >   static ssize_t
> > >   pread_mem (int fd, void *buf, size_t nbytes, uint64_t addr)
> > >   {
> > >     if (lseek (fd, (off_t) addr, SEEK_SET) == (off_t) -1)
> > >       return -1;
> > >   
> > >     return read (fd, buf, nbytes);
> > >   }
> > > 
> > 
> > Right, I missed that, and you're right. I have tested your
> > suggestion.
> > It works and is much cleaner. Sending patch v2 now.
> 
> Isn't it a kernel bug that lseek works, but not pread?
> 

Looks that way. /proc/PID/mem is marked FOP_UNSIGNED_OFFSET.
mem_lseek honors it, but ksys_pread64 rejects a negative position
unconditionally (fs/read_write.c: "if (pos < 0) return -EINVAL;"),
without consulting that flag. 
So pread and lseek disagree on the same descriptor.

For this patch, I think we just have to work around it, but I will look
into the kernel issue as well.


> Thanks,
> Florian
> 
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