Re: [PATCH 0/3] MIPS vdso and signal delivery optimization (v2)

[David Daney <ddaney@caviumnetworks.com>]

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On 02/18/2010 06:02 PM, David Daney wrote:
> Well this patch set does cause gdb to no longer be able to generate
> stack traces from signal handlers, but that just means gdb needs to be
> fixed. We will work on that next.

Attached is the corresponding gdb patch.  I will push it into the 
upstream gdb.

David Daney


>
> libgcc can unwind through signal handlers both with and without the patch.
>
> David Daney
>
>
> On 02/18/2010 04:13 PM, David Daney wrote:
>> This patch set creates a vdso and moves the signal
>> trampolines to it from their previous home on the stack.
>>
>> In the original patch set:
>> http://www.linux-mips.org/cgi-bin/mesg.cgi?a=linux-mips&i=49EE3B0F.3040506%40caviumnetworks.com
>>
>>
>> I stated:
>>
>> Tested with a 64-bit kernel on a Cavium Octeon cn3860 where I have the
>> following results from lmbench2:
>>
>> Before:
>> n64 - Signal handler overhead: 14.517 microseconds
>> n32 - Signal handler overhead: 14.497 microseconds
>> o32 - Signal handler overhead: 16.637 microseconds
>>
>> After:
>>
>> n64 - Signal handler overhead: 7.935 microseconds
>> n32 - Signal handler overhead: 7.334 microseconds
>> o32 - Signal handler overhead: 8.628 microsecond
>>
>> All that is still true.
>>
>> Improvements from the first version:
>>
>> * Compiles and runs in 32-bit kernels (on qemu at least).
>>
>> * Updated for linux-queue based 2.6.33-rc8
>>
>> David Daney (3):
>> MIPS: Add SYSCALL to uasm.
>> MIPS: Preliminary vdso.
>> MIPS: Move signal trampolines off of the stack.
>>
>> arch/mips/include/asm/abi.h | 6 +-
>> arch/mips/include/asm/elf.h | 4 +
>> arch/mips/include/asm/mmu.h | 5 +-
>> arch/mips/include/asm/mmu_context.h | 2 +-
>> arch/mips/include/asm/processor.h | 11 +++-
>> arch/mips/include/asm/uasm.h | 1 +
>> arch/mips/include/asm/vdso.h | 29 +++++++++
>> arch/mips/kernel/Makefile | 2 +-
>> arch/mips/kernel/signal-common.h | 5 --
>> arch/mips/kernel/signal.c | 86 ++++++---------------------
>> arch/mips/kernel/signal32.c | 55 ++++-------------
>> arch/mips/kernel/signal_n32.c | 26 ++------
>> arch/mips/kernel/syscall.c | 6 ++-
>> arch/mips/kernel/vdso.c | 112 +++++++++++++++++++++++++++++++++++
>> arch/mips/mm/uasm.c | 19 +++++-
>> 15 files changed, 226 insertions(+), 143 deletions(-)
>> create mode 100644 arch/mips/include/asm/vdso.h
>> create mode 100644 arch/mips/kernel/vdso.c
>>
>>
>
>


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Index: gdb/mips-linux-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/mips-linux-tdep.c,v
retrieving revision 1.81
diff -u -p -r1.81 mips-linux-tdep.c
--- gdb/mips-linux-tdep.c	1 Jan 2010 07:31:37 -0000	1.81
+++ gdb/mips-linux-tdep.c	19 Feb 2010 21:58:32 -0000
@@ -797,7 +797,7 @@ static const struct tramp_frame mips_lin
 
    struct sigframe {
      u32 sf_ass[4];            [argument save space for o32]
-     u32 sf_code[2];           [signal trampoline]
+     u32 sf_code[2];           [signal trampoline or fill]
      struct sigcontext sf_sc;
      sigset_t sf_mask;
    };
@@ -827,7 +827,7 @@ static const struct tramp_frame mips_lin
 
    struct rt_sigframe {
      u32 rs_ass[4];            [argument save space for o32]
-     u32 rs_code[2]            [signal trampoline]
+     u32 rs_code[2]            [signal trampoline or fill]
      struct siginfo rs_info;
      struct ucontext rs_uc;
    };
@@ -871,7 +871,7 @@ mips_linux_o32_sigframe_init (const stru
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   int ireg, reg_position;
-  CORE_ADDR sigcontext_base = func - SIGFRAME_CODE_OFFSET;
+  CORE_ADDR sigcontext_base = get_frame_sp (this_frame);
   const struct mips_regnum *regs = mips_regnum (gdbarch);
   CORE_ADDR regs_base;
 
@@ -1038,7 +1038,7 @@ mips_linux_n32n64_sigframe_init (const s
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   int ireg, reg_position;
-  CORE_ADDR sigcontext_base = func - SIGFRAME_CODE_OFFSET;
+  CORE_ADDR sigcontext_base =  get_frame_sp (this_frame);
   const struct mips_regnum *regs = mips_regnum (gdbarch);
 
   if (self == &mips_linux_n32_rt_sigframe)