Date:	Wed, 10 Jun 2015 13:33:34 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	vigneshr@...eaurora.org
Cc:	a.ryabinin@...sung.com, akpm@...ux-foundation.org,
	adech.fo@...il.com, Laura Abbott <labbott@...hat.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: module: Add ".ref.text" to arm unwind tables

On Wed, Jun 10, 2015 at 12:25:54PM -0000, vigneshr@...eaurora.org wrote:
> Gentle reminder for review comments.

I don't see anything wrong with the patch... but it needs to find its
way into the patch system to be applied, so it doesn't get forgotten.
Please add it there along with Laura's attributation.  Thanks.

> > 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@...hat.com>
> >>
> >>> Signed-off-by: Vignesh Radhakrishnan <vigneshr@...eaurora.org>
> >>> ---
> >>>   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
> >
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >
> 
> 

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