Messages in this thread Patch in this message | | | From | Jiri Olsa <> | Subject | [RFC 09/23] x86_64: Store userspace rsp in system_call fastpath | Date | Tue, 19 Jun 2012 17:48:00 +0200 |
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hi, I'd need help with this change.. basically it works, but I guess I could alter the FIXUP_TOP_OF_STACK macro as well, so the rsp is not initialized twice in slowpath.
But it seems quite complex.. so not really sure at the moment ;)
ideas?
thanks, jirka
--- Storing the userspace rsp into the pt_regs struct for the system_call fastpath (syscall instruction handler).
Following part of the pt_regs is allocated on stack: (via KERNEL_STACK_OFFSET)
unsigned long ip; unsigned long cs; unsigned long flags; unsigned long sp; unsigned long ss;
but only ip is actually saved for fastpath.
For perf post unwind we need at least ip and sp to be able to start the unwind, so storing the old_rsp value to the sp.
Signed-off-by: Jiri Olsa <jolsa@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Roland McGrath <roland@hack.frob.com> --- arch/x86/kernel/entry_64.S | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 111f6bb..0444917 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -516,6 +516,11 @@ GLOBAL(system_call_after_swapgs) SAVE_ARGS 8,0 movq %rax,ORIG_RAX-ARGOFFSET(%rsp) movq %rcx,RIP-ARGOFFSET(%rsp) +#ifdef CONFIG_PERF_EVENTS + /* We need rsp in fast path for perf post unwind. */ + movq PER_CPU_VAR(old_rsp), %rcx + movq %rcx,RSP-ARGOFFSET(%rsp) +#endif CFI_REL_OFFSET rip,RIP-ARGOFFSET testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz tracesys -- 1.7.7.6
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