Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [3.13.y-ckt stable] Patch "ARC: make sure instruction_pointer() returns unsigned value" has been added to staging queue | Date | Thu, 6 Aug 2015 13:37:03 -0700 |
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This is a note to let you know that I have just added a patch titled
ARC: make sure instruction_pointer() returns unsigned value
to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue
This patch is scheduled to be released in version 3.13.11-ckt25.
If you, or anyone else, feels it should not be added to this tree, please reply to this email.
For more information about the 3.13.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks. -Kamal
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From 7d8aeaab15e7b8d2da62c63599e61143d2252939 Mon Sep 17 00:00:00 2001 From: Alexey Brodkin <abrodkin@synopsys.com> Date: Mon, 13 Jul 2015 10:25:17 +0300 Subject: ARC: make sure instruction_pointer() returns unsigned value
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 <abrodkin@synopsys.com> Cc: arc-linux-dev@synopsys.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/arc/include/asm/ptrace.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h index 1bfeec2..2a58af7 100644 --- a/arch/arc/include/asm/ptrace.h +++ b/arch/arc/include/asm/ptrace.h @@ -63,7 +63,7 @@ struct callee_regs { long r25, r24, r23, r22, r21, r20, r19, r18, r17, r16, r15, r14, 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 */ -- 1.9.1
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