Re: [PATCH] ARM: module: Add ".ref.text" to arm unwind tables
From: Laura Abbott
Date: Thu May 14 2015 - 17:23:56 EST
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++)
--
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