From: Nathan_Lynch@mentor•com (Nathan Lynch)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v7 7/9] ARM: add vdso user-space code
Date: Sat, 28 Jun 2014 10:19:53 -0500 [thread overview]
Message-ID: <53AEDD19.80808@mentor.com> (raw)
In-Reply-To: <20140628095314.GC32514@n2100.arm.linux.org.uk>
On 06/28/2014 04:53 AM, Russell King - ARM Linux wrote:
> On Sun, Jun 22, 2014 at 10:11:56PM -0500, Nathan Lynch wrote:
>> Place vdso-related user-space code in arch/arm/kernel/vdso/.
>>
>> It is almost completely written in C with some assembly helpers to
>> load the data page address, sample the counter, and fall back to
>> system calls when necessary.
>>
>> If CONFIG_ARM_ARCH_TIMER is not enabled, the vdso cannot service
>> high-resolution clocks and falls back to syscalls. Low-resolution
>> clocks e.g. CLOCK_REALTIME_COARSE can be serviced regardless.
>>
>> Of particular note is that a post-processing step ("vdsomunge") is
>> necessary to produce a shared object which is architecturally allowed
>> to be used by both soft- and hard-float EABI programs.
>>
>> The 2012 edition of the ARM ABI defines Tag_ABI_VFP_args = 3 "Code is
>> compatible with both the base and VFP variants; the user did not
>> permit non-variadic functions to pass FP parameters/results."
>> Unfortunately current toolchains do not support this tag, which is
>> ideally what we would use.
>>
>> The best available option is to ensure that both EF_ARM_ABI_FLOAT_SOFT
>> and EF_ARM_ABI_FLOAT_HARD are unset in the ELF header's e_flags,
>> indicating that the shared object is "old" and should be accepted for
>> backward compatibility's sake. While binutils < 2.24 appear to
>> produce a vdso.so with both flags clear, 2.24 always sets
>> EF_ARM_ABI_FLOAT_SOFT, with no way to inhibit this behavior. So we
>> have to fix things up with a custom post-processing step.
>>
>> In fact, the VDSO code in glibc does much less validation (including
>> checking these flags) than the code for handling conventional
>> file-backed shared libraries, so this is a bit moot unless glibc's
>> VDSO code becomes more strict.
>>
>> Signed-off-by: Nathan Lynch <nathan_lynch@mentor•com>
>> ---
>> arch/arm/kernel/asm-offsets.c | 5 +
>> arch/arm/kernel/vdso/.gitignore | 1 +
>> arch/arm/kernel/vdso/Makefile | 59 +++++++
>> arch/arm/kernel/vdso/checkundef.sh | 9 +
>> arch/arm/kernel/vdso/datapage.S | 15 ++
>> arch/arm/kernel/vdso/vdso.S | 35 ++++
>> arch/arm/kernel/vdso/vdso.lds.S | 88 ++++++++++
>> arch/arm/kernel/vdso/vdsomunge.c | 193 +++++++++++++++++++++
>> arch/arm/kernel/vdso/vgettimeofday.c | 320 +++++++++++++++++++++++++++++++++++
>> 9 files changed, 725 insertions(+)
>> create mode 100644 arch/arm/kernel/vdso/.gitignore
>> create mode 100644 arch/arm/kernel/vdso/Makefile
>> create mode 100755 arch/arm/kernel/vdso/checkundef.sh
>> create mode 100644 arch/arm/kernel/vdso/datapage.S
>> create mode 100644 arch/arm/kernel/vdso/vdso.S
>> create mode 100644 arch/arm/kernel/vdso/vdso.lds.S
>> create mode 100644 arch/arm/kernel/vdso/vdsomunge.c
>> create mode 100644 arch/arm/kernel/vdso/vgettimeofday.c
>
> One change I would like to see (to stop the directory tree getting soo
> deep) is to move this to arch/arm/vdso - just like x86 is arch/x86/vdso.
> Was there a pressing reason to have it in arch/arm/kernel ?
No pressing reason. I think I was just following the example of non-x86
architectures. I can move it to arch/arm/vdso.
next prev parent reply other threads:[~2014-06-28 15:19 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-23 3:11 [PATCH v7 0/9] ARM: VDSO Nathan Lynch
2014-06-23 3:11 ` [PATCH v7 1/9] clocksource: arm_arch_timer: change clocksource name if CP15 unavailable Nathan Lynch
2014-06-23 3:11 ` [PATCH v7 2/9] clocksource: arm_arch_timer: enable counter access for 32-bit ARM Nathan Lynch
2014-06-23 3:11 ` [PATCH v7 3/9] ARM: arch_timer: remove unused functions Nathan Lynch
2014-06-23 3:11 ` [PATCH v7 4/9] arm64: " Nathan Lynch
2014-06-23 3:11 ` [PATCH v7 5/9] ARM: place sigpage at a random offset above stack Nathan Lynch
2014-06-23 3:11 ` [PATCH v7 6/9] ARM: miscellaneous vdso infrastructure, preparation Nathan Lynch
2014-06-30 10:11 ` Arnd Bergmann
2014-06-30 12:27 ` Nathan Lynch
2014-06-30 13:06 ` Arnd Bergmann
2014-06-23 3:11 ` [PATCH v7 7/9] ARM: add vdso user-space code Nathan Lynch
2014-06-28 9:53 ` Russell King - ARM Linux
2014-06-28 10:03 ` Russell King - ARM Linux
2014-06-30 15:56 ` Andy Lutomirski
2014-06-28 15:19 ` Nathan Lynch [this message]
2014-06-28 15:26 ` Russell King - ARM Linux
2014-06-28 16:13 ` Nathan Lynch
2014-06-28 18:12 ` Russell King - ARM Linux
2014-06-28 19:45 ` Nathan Lynch
2014-06-28 20:11 ` Russell King - ARM Linux
2014-06-28 21:35 ` Nathan Lynch
2014-06-29 8:34 ` Russell King - ARM Linux
2014-06-29 15:48 ` Nathan Lynch
2014-06-29 16:07 ` Russell King - ARM Linux
2014-06-29 23:04 ` Nathan Lynch
2014-06-30 21:33 ` Andy Lutomirski
2014-06-30 15:59 ` Andy Lutomirski
2014-06-30 16:50 ` Nathan Lynch
2014-06-30 21:29 ` Andy Lutomirski
2014-07-01 9:00 ` Will Deacon
2014-07-01 13:34 ` Nathan Lynch
2014-07-01 14:11 ` Andy Lutomirski
2014-07-01 13:28 ` Nathan Lynch
2014-07-01 14:56 ` Andy Lutomirski
2014-06-23 3:11 ` [PATCH v7 8/9] ARM: vdso initialization, mapping, and synchronization Nathan Lynch
2014-06-30 21:37 ` Andy Lutomirski
2014-07-01 9:03 ` Will Deacon
2014-07-01 14:11 ` Nathan Lynch
2014-07-01 14:15 ` Will Deacon
2014-07-01 14:17 ` Andy Lutomirski
2014-07-01 17:27 ` Christopher Covington
2014-07-02 14:40 ` Will Deacon
2014-07-02 15:54 ` Andy Lutomirski
2014-07-02 16:18 ` Nathan Lynch
2014-07-02 16:27 ` Will Deacon
2014-07-02 16:47 ` Andy Lutomirski
2014-07-02 17:24 ` Will Deacon
2014-07-02 18:34 ` Andy Lutomirski
2014-07-02 18:54 ` Will Deacon
2014-07-22 0:14 ` Andy Lutomirski
2014-07-22 8:13 ` Will Deacon
2014-07-01 14:01 ` Nathan Lynch
2014-07-01 14:09 ` Andy Lutomirski
2014-07-01 14:14 ` Russell King - ARM Linux
2014-06-23 3:11 ` [PATCH v7 9/9] ARM: add CONFIG_VDSO Kconfig and Makefile bits Nathan Lynch
2014-06-27 8:51 ` [PATCH v7 0/9] ARM: VDSO Jan Glauber
2014-06-27 8:57 ` Russell King - ARM Linux
2014-06-27 9:41 ` Ard Biesheuvel
2014-06-27 9:46 ` Russell King - ARM Linux
2014-06-27 17:01 ` Nathan Lynch
2014-06-28 9:42 ` Russell King - ARM Linux
2014-06-28 9:55 ` Russell King - ARM Linux
2014-06-28 14:49 ` Russell King - ARM Linux
2014-06-30 7:27 ` Arnd Bergmann
2014-06-30 7:43 ` Arnd Bergmann
2014-06-30 18:27 ` Nathan Lynch
2014-06-27 16:00 ` Nathan Lynch
2014-06-30 16:03 ` Andy Lutomirski
2014-06-30 8:12 ` Ard Biesheuvel
2014-07-01 16:34 ` Nathan Lynch
2014-07-01 20:08 ` Ard Biesheuvel
2014-07-01 22:44 ` Russell King - ARM Linux
2014-06-30 14:40 ` Will Deacon
2014-06-30 15:42 ` Nathan Lynch
2014-06-30 21:56 ` Andy Lutomirski
2014-07-01 9:04 ` Will Deacon
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