Re: [PATCH v3] mips: dl-machine-reject-phdr: Get rid of alloca.

["Ying Huang" <ying.huang@oss.cipunited.com>]

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Hi,

I have tested this patch on my lab, the resutls of make and make check all were good.

And make check did not introduce new XFAILS.

The environment is:

gcc 12.2.0, binutils 2.40, mips64el-linux-gnuabi64


Thanks,

Ying


在 2023/8/30 03:30, Joe Simmons-Talbott via Libc-alpha 写道:
> Ping.
>
> On Mon, Jun 26, 2023 at 09:16:21AM -0400, Joe Simmons-Talbott wrote:
>> Read directly into the mips_abiflags struct rather than reading the
>> entire segment and using alloca when the passed buffer is not big enough.
>>
>> Checked with build-many-glibcs.py on mips-linux-gnu
>> ---
>> Changes to v2:
>>   * Rather than use a scratch buffer use the mips_abiflags struct itself
>>     for reading since we're now just reading that much data and not the
>>     whole segment.
>>
>>  sysdeps/mips/dl-machine-reject-phdr.h | 26 ++++++++++----------------
>>  1 file changed, 10 insertions(+), 16 deletions(-)
>>
>> diff --git a/sysdeps/mips/dl-machine-reject-phdr.h b/sysdeps/mips/dl-machine-reject-phdr.h
>> index 104b590661..b784697fc1 100644
>> --- a/sysdeps/mips/dl-machine-reject-phdr.h
>> +++ b/sysdeps/mips/dl-machine-reject-phdr.h
>> @@ -161,7 +161,7 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
>>    Lmid_t nsid;
>>    int in_abi = -1;
>>    struct abi_req in_req;
>> -  Elf_MIPS_ABIFlags_v0 *mips_abiflags = NULL;
>> +  Elf_MIPS_ABIFlags_v0 mips_abiflags;
>>    bool perfect_match = false;
>>  #if _MIPS_SIM == _ABIO32
>>    unsigned int cur_mode = -1;
>> @@ -176,25 +176,19 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
>>    /* Read the attributes section.  */
>>    if (ph != NULL)
>>      {
>> -      ElfW(Addr) size = ph->p_filesz;
>> +      ElfW(Addr) size = sizeof (Elf_MIPS_ABIFlags_v0);
>>  
>> -      if (ph->p_offset + size <= len)
>> -	mips_abiflags = (Elf_MIPS_ABIFlags_v0 *) (buf + ph->p_offset);
>> -      else
>> -	{
>> -	  mips_abiflags = alloca (size);
>> -	  __lseek (fd, ph->p_offset, SEEK_SET);
>> -	  if (__libc_read (fd, (void *) mips_abiflags, size) != size)
>> -	    REJECT ("   unable to read PT_MIPS_ABIFLAGS\n");
>> -	}
>> -
>> -      if (size < sizeof (Elf_MIPS_ABIFlags_v0))
>> +      if (ph->p_filesz < size)
>>  	REJECT ("   contains malformed PT_MIPS_ABIFLAGS\n");
>>  
>> -      if (__glibc_unlikely (mips_abiflags->flags2 != 0))
>> -	REJECT ("   unknown MIPS.abiflags flags2: %u\n", mips_abiflags->flags2);
>> +      __lseek (fd, ph->p_offset, SEEK_SET);
>> +      if (__libc_read (fd, (void *) &mips_abiflags, size) != size)
>> +	REJECT ("   unable to read PT_MIPS_ABIFLAGS\n");
>> +
>> +      if (__glibc_unlikely (mips_abiflags.flags2 != 0))
>> +	REJECT ("   unknown MIPS.abiflags flags2: %u\n", mips_abiflags.flags2);
>>  
>> -      in_abi = mips_abiflags->fp_abi;
>> +      in_abi = mips_abiflags.fp_abi;
>>      }
>>  
>>    /* ANY is compatible with anything.  */
>> -- 
>> 2.39.2
>>