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From: Nikola Veljkovic <Nikola.Veljkovic@imgtec.com>
To: "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>
Cc: "ralf@linux-mips.org" <ralf@linux-mips.org>,
	Chris Dearman <Chris.Dearman@imgtec.com>,
	Raghu Gandham <Raghu.Gandham@imgtec.com>,
	Miodrag Dinic <Miodrag.Dinic@imgtec.com>,
	Petar Jovanovic <Petar.Jovanovic@imgtec.com>,
	Lazar Trsic <Lazar.Trsic@imgtec.com>
Subject: [PATCH] MIPS: personality syscall discrepancy on mips64-o32/n32
Date: Tue, 18 Aug 2015 10:25:31 +0000	[thread overview]
Message-ID: <19CDB9880DBFC241860D925D8FAA94A00342EAB8@BADAG02.ba.imgtec.org> (raw)

There is a discrepancy in the personality() syscall on mips64.

For a 32bit process (o32 or n32) sys_32_personality() [1] is called, which
converts PER_LINUX32 -> PER_LINUX:

ret = sys_personality(p);
if (ret != -1 && (ret & PER_MASK) == PER_LINUX32)  // personality macro applied
   ret = (ret & ~PER_MASK) | PER_LINUX;            // to make it clearer

This is different than what Intel and ARM are doing. They directly invoke
sys_personality(). On Android, this causes a bionic test to fail for mips, as it
expects PER_LINUX32 but receives PER_LINUX, when ran on mips64 core.

The code itself comes from older kernel versions (2.4), where it was also used
by other architectures [2], [3], [4]. However, since kernel 2.6 other archs are
invoking sys_personality() directly, for all ABIs.

Is there any reason why we should do PER_LINUX32 -> PER_LINUX on mips? Also, if
we do change this for o32, should we change it for n32, as well? There is no n32
support for Android, so it would have to be tested elsewhere.

Tested changing only o32 on Android, there were no regressions:

diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index ab93427..b94ee4e 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -358,7 +358,7 @@ sys_call_table:
        sys     sys_fchdir              1
        sys     sys_bdflush             2
        sys     sys_sysfs               3       /* 4135 */
-       sys     sys_32_personality      1
+       sys     sys_personality         1
        sys     sys_ni_syscall          0       /* for afs_syscall */
        sys     sys_setfsuid            1
        sys     sys_setfsgid            1
--

[1] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/mips/kernel/linux32.c#n122
[2] http://git.linux-mips.org/cgit/ralf/linux.git/tree/include/asm-mips64/elf.h?h=linux-2.4#n124
[3] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/x86_64/ia32/sys_ia32.c?h=linux-2.4#n1974
[4] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/ia64/ia32/sys_ia32.c?h=linux-2.4#n4005
--
Nikola Veljkovic
From Markos.Chandras@imgtec.com Tue Aug 18 14:56:12 2015
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Date:   Tue, 18 Aug 2015 13:56:05 +0100
From:   Markos Chandras <markos.chandras@imgtec.com>
To:     Nikola Veljkovic <Nikola.Veljkovic@imgtec.com>
CC:     "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>,
        "ralf@linux-mips.org" <ralf@linux-mips.org>,
        Chris Dearman <Chris.Dearman@imgtec.com>,
        Raghu Gandham <Raghu.Gandham@imgtec.com>,
        "Miodrag Dinic" <Miodrag.Dinic@imgtec.com>,
        Petar Jovanovic <Petar.Jovanovic@imgtec.com>,
        Lazar Trsic <Lazar.Trsic@imgtec.com>
Subject: Re: [PATCH] MIPS: personality syscall discrepancy on mips64-o32/n32
Message-ID: <20150818125605.GA25978@mchandras-linux.le.imgtec.org>
References: <19CDB9880DBFC241860D925D8FAA94A00342EAB8@BADAG02.ba.imgtec.org>
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On Tue, Aug 18, 2015 at 10:25:31AM +0000, Nikola Veljkovic wrote:
> There is a discrepancy in the personality() syscall on mips64.
> 
> For a 32bit process (o32 or n32) sys_32_personality() [1] is called, which
> converts PER_LINUX32 -> PER_LINUX:
> 
> ret = sys_personality(p);
> if (ret != -1 && (ret & PER_MASK) == PER_LINUX32)  // personality macro applied
>    ret = (ret & ~PER_MASK) | PER_LINUX;            // to make it clearer
> 
> This is different than what Intel and ARM are doing. They directly invoke
> sys_personality(). On Android, this causes a bionic test to fail for mips, as it
> expects PER_LINUX32 but receives PER_LINUX, when ran on mips64 core.
> 
> The code itself comes from older kernel versions (2.4), where it was also used
> by other architectures [2], [3], [4]. However, since kernel 2.6 other archs are
> invoking sys_personality() directly, for all ABIs.
> 
> Is there any reason why we should do PER_LINUX32 -> PER_LINUX on mips? Also, if
> we do change this for o32, should we change it for n32, as well? There is no n32
> support for Android, so it would have to be tested elsewhere.
> 
> Tested changing only o32 on Android, there were no regressions:
> 
> diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> index ab93427..b94ee4e 100644
> --- a/arch/mips/kernel/scall64-o32.S
> +++ b/arch/mips/kernel/scall64-o32.S
> @@ -358,7 +358,7 @@ sys_call_table:
>         sys     sys_fchdir              1
>         sys     sys_bdflush             2
>         sys     sys_sysfs               3       /* 4135 */
> -       sys     sys_32_personality      1
> +       sys     sys_personality         1
>         sys     sys_ni_syscall          0       /* for afs_syscall */
>         sys     sys_setfsuid            1
>         sys     sys_setfsgid            1
> --
> 
> [1] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/mips/kernel/linux32.c#n122
> [2] http://git.linux-mips.org/cgit/ralf/linux.git/tree/include/asm-mips64/elf.h?h=linux-2.4#n124
> [3] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/x86_64/ia32/sys_ia32.c?h=linux-2.4#n1974
> [4] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/ia64/ia32/sys_ia32.c?h=linux-2.4#n4005
> --
> Nikola Veljkovic

Hi,

I am not sure what the implication will be to userland with that change...

I presume you also need to fix the n32 case and then completely remove the sys_32_personality
syscall from linux32.c. Moreover, I think you also need to fix the arch/mips/include/asm/elf.h
code to set LINUX32 for O32 and n32 (for both 32b and 64b kernels.)

If you are going to submit a new patch, can you please create a proper git patch
(using git format-patch) and include your Signed-off-by line as well? Thank you

-- 
markos

WARNING: multiple messages have this Message-ID
From: Nikola Veljkovic <Nikola.Veljkovic@imgtec.com>
To: "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>
Cc: "ralf@linux-mips.org" <ralf@linux-mips.org>,
	Chris Dearman <Chris.Dearman@imgtec.com>,
	Raghu Gandham <Raghu.Gandham@imgtec.com>,
	Miodrag Dinic <Miodrag.Dinic@imgtec.com>,
	Petar Jovanovic <Petar.Jovanovic@imgtec.com>,
	Lazar Trsic <Lazar.Trsic@imgtec.com>
Subject: [PATCH] MIPS: personality syscall discrepancy on mips64-o32/n32
Date: Tue, 18 Aug 2015 10:25:31 +0000	[thread overview]
Message-ID: <19CDB9880DBFC241860D925D8FAA94A00342EAB8@BADAG02.ba.imgtec.org> (raw)
Message-ID: <20150818102531.82F0NmGjNm4bbJNUzVkaNhkXlX_FZXCa8DgXGt_dZrw@z> (raw)

There is a discrepancy in the personality() syscall on mips64.

For a 32bit process (o32 or n32) sys_32_personality() [1] is called, which
converts PER_LINUX32 -> PER_LINUX:

ret = sys_personality(p);
if (ret != -1 && (ret & PER_MASK) == PER_LINUX32)  // personality macro applied
   ret = (ret & ~PER_MASK) | PER_LINUX;            // to make it clearer

This is different than what Intel and ARM are doing. They directly invoke
sys_personality(). On Android, this causes a bionic test to fail for mips, as it
expects PER_LINUX32 but receives PER_LINUX, when ran on mips64 core.

The code itself comes from older kernel versions (2.4), where it was also used
by other architectures [2], [3], [4]. However, since kernel 2.6 other archs are
invoking sys_personality() directly, for all ABIs.

Is there any reason why we should do PER_LINUX32 -> PER_LINUX on mips? Also, if
we do change this for o32, should we change it for n32, as well? There is no n32
support for Android, so it would have to be tested elsewhere.

Tested changing only o32 on Android, there were no regressions:

diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index ab93427..b94ee4e 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -358,7 +358,7 @@ sys_call_table:
        sys     sys_fchdir              1
        sys     sys_bdflush             2
        sys     sys_sysfs               3       /* 4135 */
-       sys     sys_32_personality      1
+       sys     sys_personality         1
        sys     sys_ni_syscall          0       /* for afs_syscall */
        sys     sys_setfsuid            1
        sys     sys_setfsgid            1
--

[1] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/mips/kernel/linux32.c#n122
[2] http://git.linux-mips.org/cgit/ralf/linux.git/tree/include/asm-mips64/elf.h?h=linux-2.4#n124
[3] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/x86_64/ia32/sys_ia32.c?h=linux-2.4#n1974
[4] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/ia64/ia32/sys_ia32.c?h=linux-2.4#n4005
--
Nikola Veljkovic

             reply	other threads:[~2015-08-18 10:25 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-08-18 10:25 Nikola Veljkovic [this message]
2015-08-18 10:25 ` [PATCH] MIPS: personality syscall discrepancy on mips64-o32/n32 Nikola Veljkovic
2015-08-18 12:56 ` Markos Chandras
2015-08-20 14:46   ` Nikola Veljkovic
2015-08-20 14:46     ` Nikola Veljkovic
2015-11-12 16:25     ` Ralf Baechle
2015-11-12 19:50       ` Nikola Veljkovic
2015-11-12 19:50         ` Nikola Veljkovic

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