This is a note to let you know that I've just added the patch titled
ARC: make sure instruction_pointer() returns unsigned value
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arc-make-sure-instruction_pointer-returns-unsigned-value.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From f51e2f1911122879eefefa4c592dea8bf794b39c Mon Sep 17 00:00:00 2001
From: Alexey Brodkin <[email protected]>
Date: Mon, 13 Jul 2015 10:25:17 +0300
Subject: ARC: make sure instruction_pointer() returns unsigned value
From: Alexey Brodkin <[email protected]>
commit f51e2f1911122879eefefa4c592dea8bf794b39c upstream.
Currently instruction_pointer() returns pt_regs->ret and so return value
is of type "long", which implicitly stands for "signed long".
While that's perfectly fine when dealing with 32-bit values if return
value of instruction_pointer() gets assigned to 64-bit variable sign
extension may happen.
And at least in one real use-case it happens already.
In perf_prepare_sample() return value of perf_instruction_pointer()
(which is an alias to instruction_pointer() in case of ARC) is assigned
to (struct perf_sample_data)->ip (which type is "u64").
And what we see if instuction pointer points to user-space application
that in case of ARC lays below 0x8000_0000 "ip" gets set properly with
leading 32 zeros. But if instruction pointer points to kernel address
space that starts from 0x8000_0000 then "ip" is set with 32 leadig
"f"-s. I.e. id instruction_pointer() returns 0x8100_0000, "ip" will be
assigned with 0xffff_ffff__8100_0000. Which is obviously wrong.
In particular that issuse broke output of perf, because perf was unable
to associate addresses like 0xffff_ffff__8100_0000 with anything from
/proc/kallsyms.
That's what we used to see:
----------->8----------
6.27% ls [unknown] [k] 0xffffffff8046c5cc
2.96% ls libuClibc-0.9.34-git.so [.] memcpy
2.25% ls libuClibc-0.9.34-git.so [.] memset
1.66% ls [unknown] [k] 0xffffffff80666536
1.54% ls libuClibc-0.9.34-git.so [.] 0x000224d6
1.18% ls libuClibc-0.9.34-git.so [.] 0x00022472
----------->8----------
With that change perf output looks much better now:
----------->8----------
8.21% ls [kernel.kallsyms] [k] memset
3.52% ls libuClibc-0.9.34-git.so [.] memcpy
2.11% ls libuClibc-0.9.34-git.so [.] malloc
1.88% ls libuClibc-0.9.34-git.so [.] memset
1.64% ls [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore
1.41% ls [kernel.kallsyms] [k] __d_lookup_rcu
----------->8----------
Signed-off-by: Alexey Brodkin <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Vineet Gupta <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/arc/include/asm/ptrace.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -83,7 +83,7 @@ struct callee_regs {
long r13;
};
-#define instruction_pointer(regs) ((regs)->ret)
+#define instruction_pointer(regs) (unsigned long)((regs)->ret)
#define profile_pc(regs) instruction_pointer(regs)
/* return 1 if user mode or 0 if kernel mode */
Patches currently in stable-queue which might be from [email protected] are
queue-3.10/arc-make-sure-instruction_pointer-returns-unsigned-value.patch
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