Re: [PATCH] ARM: module: Add ".ref.text" to arm unwind tables

[vigneshr]

Gentle reminder for review comments.

> Forgot to add Maintainers. Adding them now.
>
>> On 05/13/2015 08:20 AM, Vignesh Radhakrishnan wrote:
>>> Functions inside kernel modules that use __ref
>>> will end up being placed in .ARM.exidx.ref.text
>>> section by gcc.
>>>
>>> Currently we don't consider adding these functions
>>> to arm unwind tables.
>>>
>>> Hence, if we turn slub debug on by default we end up
>>> with the messages of this sort:
>>>
>>> 	unwind: Index not found bf0011e0
>>>
>>> This is because slub debug saves stack trace of
>>> allocation's and free's. Therefore, we end up seeing
>>> a flood of these messages in dmesg since its not
>>> able to locate these functions.
>>>
>>> Fix this by adding .ref.text section to arm unwind tables.
>>>
>>
>> With this patch, I go from
>>
>>   ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 63 at drivers/misc/test.c:12
>> that_function+0x10/0x2c
>> [test]()
>> Modules linked in: test(P+)
>> CPU: 0 PID: 63 Comm: insmod Tainted: P                4.1.0-rc2+ #28
>> Hardware name: ARM-Versatile PB
>> [<c001a590>] (unwind_backtrace) from [<c0017b84>] (show_stack+0x10/0x14)
>> [<c0017b84>] (show_stack) from [<c0022370>]
>> (warn_slowpath_common+0x78/0xb0)
>> [<c0022370>] (warn_slowpath_common) from [<c0022444>]
>> (warn_slowpath_null+0x1c/0x24)
>> [<c0022444>] (warn_slowpath_null) from [<bf000048>]
>> (that_function+0x10/0x2c [test])
>> unwind: Index not found bf000048
>> ---[ end trace 3e24f8edd90f3b27 ]---
>>
>> to
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 63 at drivers/misc/test.c:12
>> that_function+0x10/0x2c
>> [test]()
>> Modules linked in: test(P+)
>> CPU: 0 PID: 63 Comm: insmod Tainted: P                4.1.0-rc2+ #30
>> Hardware name: ARM-Versatile PB
>> [<c001a5d0>] (unwind_backtrace) from [<c0017b84>] (show_stack+0x10/0x14)
>> [<c0017b84>] (show_stack) from [<c0022770>]
>> (warn_slowpath_common+0x78/0xb0)
>> [<c0022770>] (warn_slowpath_common) from [<c0022844>]
>> (warn_slowpath_null+0x1c/0x24)
>> [<c0022844>] (warn_slowpath_null) from [<bf000048>]
>> (that_function+0x10/0x2c [test])
>> [<bf000048>] (that_function [test]) from [<bf002010>]
>> (awesome_module+0x10/0x1c [test])
>> [<bf002010>] (awesome_module [test]) from [<c0009710>]
>> (do_one_initcall+0x80/0x1dc)
>> [<c0009710>] (do_one_initcall) from [<c02d14e0>]
>> (do_init_module+0x58/0x1a8)
>> [<c02d14e0>] (do_init_module) from [<c0063940>]
>> (load_module+0x170c/0x1c38)
>> [<c0063940>] (load_module) from [<c0063f38>]
>> (SyS_init_module+0xcc/0x124)
>> [<c0063f38>] (SyS_init_module) from [<c0014900>]
>> (ret_fast_syscall+0x0/0x30)
>> ---[ end trace 554c9ff461eb2505 ]---
>>
>> Tested-by: Laura Abbott <labbott@xxxxxxxxxx>
>>
>>> Signed-off-by: Vignesh Radhakrishnan <vigneshr@xxxxxxxxxxxxxx>
>>> ---
>>>   arch/arm/include/asm/module.h | 1 +
>>>   arch/arm/kernel/module.c      | 4 ++++
>>>   2 files changed, 5 insertions(+)
>>>
>>> diff --git a/arch/arm/include/asm/module.h
>>> b/arch/arm/include/asm/module.h
>>> index ed690c4..17640c9 100644
>>> --- a/arch/arm/include/asm/module.h
>>> +++ b/arch/arm/include/asm/module.h
>>> @@ -14,6 +14,7 @@ enum {
>>>   	ARM_SEC_DEVEXIT,
>>>   	ARM_SEC_HOT,
>>>   	ARM_SEC_UNLIKELY,
>>> +	ARM_SEC_REF,
>>>   	ARM_SEC_MAX,
>>>   };
>>>
>>> diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
>>> index 2e11961..846b888 100644
>>> --- a/arch/arm/kernel/module.c
>>> +++ b/arch/arm/kernel/module.c
>>> @@ -308,6 +308,8 @@ int module_finalize(const Elf32_Ehdr *hdr, const
>>> Elf_Shdr *sechdrs,
>>>   			maps[ARM_SEC_UNLIKELY].unw_sec = s;
>>>   		else if (strcmp(".ARM.exidx.text.hot", secname) == 0)
>>>   			maps[ARM_SEC_HOT].unw_sec = s;
>>> +		else if (strcmp(".ARM.exidx.ref.text", secname) == 0)
>>> +			maps[ARM_SEC_REF].unw_sec = s;
>>>   		else if (strcmp(".init.text", secname) == 0)
>>>   			maps[ARM_SEC_INIT].txt_sec = s;
>>>   		else if (strcmp(".text", secname) == 0)
>>> @@ -318,6 +320,8 @@ int module_finalize(const Elf32_Ehdr *hdr, const
>>> Elf_Shdr *sechdrs,
>>>   			maps[ARM_SEC_UNLIKELY].txt_sec = s;
>>>   		else if (strcmp(".text.hot", secname) == 0)
>>>   			maps[ARM_SEC_HOT].txt_sec = s;
>>> +		else if (strcmp(".ref.text", secname) == 0)
>>> +			maps[ARM_SEC_REF].txt_sec = s;
>>>   	}
>>>
>>>   	for (i = 0; i < ARM_SEC_MAX; i++)
>>>
>>
>>
>
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of the Code Aurora Forum, hosted by The Linux Foundation.
> again
>
>
>
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