From: Alexey Brodkin <abrodkin@xxxxxxxxxxxx> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== 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@xxxxxxxxxxxx> Cc: arc-linux-dev@xxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- 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 1bfeec2c0558..2a58af7a2e3a 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 */ -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html