From 625dbc3b8acbefefefe27e1d7bbc6e53eb4f3f2d Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 6 Jan 2011 15:22:47 +0100 Subject: [PATCH] x86: Save rbp in pt_regs on irq entry From the x86_64 low level interrupt handlers, the frame pointer is saved right after the partial pt_regs frame. rbp is not supposed to be part of the irq partial saved registers, but it only requires to extend the pt_regs frame by 8 bytes to do so, plus a tiny stack offset fixup on irq exit. This changes a bit the semantics or get_irq_entry() that is supposed to provide only the value of caller saved registers and the cpu saved frame. However it's a win for unwinders that can walk through stack frames on top of get_irq_regs() snapshots. A noticeable impact is that it makes perf events cpu-clock and task-clock events based callchains working on x86_64. Let's then save rbp into the irq pt_regs. As a result with: perf record -e cpu-clock perf bench sched messaging perf report --stdio Before: 20.94% perf [kernel.kallsyms] [k] lock_acquire | --- lock_acquire | |--44.01%-- __write_nocancel | |--43.18%-- __read | |--6.08%-- fork | create_worker | |--0.88%-- _dl_fixup | |--0.65%-- do_lookup_x | |--0.53%-- __GI___libc_read --4.67%-- [...] After: 19.23% perf [kernel.kallsyms] [k] __lock_acquire | --- __lock_acquire | |--97.74%-- lock_acquire | | | |--21.82%-- _raw_spin_lock | | | | | |--37.26%-- unix_stream_recvmsg | | | sock_aio_read | | | do_sync_read | | | vfs_read | | | sys_read | | | system_call | | | __read | | | | | |--24.09%-- unix_stream_sendmsg | | | sock_aio_write | | | do_sync_write | | | vfs_write | | | sys_write | | | system_call | | | __write_nocancel v2: Fix cfi annotations. Reported-by: Soeren Sandmann Pedersen Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Thomas Gleixner Cc: H. Peter Anvin Cc: Arnaldo Carvalho de Melo Cc: Stephane Eranian Cc: Jan Beulich --- arch/x86/kernel/entry_64.S | 36 +++++++++++++++++++++++------------- 1 file changed, 23 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index e3ba417e8697..d3b895f375d3 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -299,17 +299,21 @@ ENDPROC(native_usergs_sysret64) ENTRY(save_args) XCPT_FRAME cld - movq_cfi rdi, RDI+16-ARGOFFSET - movq_cfi rsi, RSI+16-ARGOFFSET - movq_cfi rdx, RDX+16-ARGOFFSET - movq_cfi rcx, RCX+16-ARGOFFSET - movq_cfi rax, RAX+16-ARGOFFSET - movq_cfi r8, R8+16-ARGOFFSET - movq_cfi r9, R9+16-ARGOFFSET - movq_cfi r10, R10+16-ARGOFFSET - movq_cfi r11, R11+16-ARGOFFSET - - leaq -ARGOFFSET+16(%rsp),%rdi /* arg1 for handler */ + /* + * start from rbp in pt_regs and jump over + * return address. + */ + movq_cfi rdi, RDI+8-RBP + movq_cfi rsi, RSI+8-RBP + movq_cfi rdx, RDX+8-RBP + movq_cfi rcx, RCX+8-RBP + movq_cfi rax, RAX+8-RBP + movq_cfi r8, R8+8-RBP + movq_cfi r9, R9+8-RBP + movq_cfi r10, R10+8-RBP + movq_cfi r11, R11+8-RBP + + leaq -RBP+8(%rsp),%rdi /* arg1 for handler */ movq_cfi rbp, 8 /* push %rbp */ leaq 8(%rsp), %rbp /* mov %rsp, %ebp */ testl $3, CS(%rdi) @@ -782,8 +786,9 @@ END(interrupt) /* 0(%rsp): ~(interrupt number) */ .macro interrupt func - subq $ORIG_RAX-ARGOFFSET+8, %rsp - CFI_ADJUST_CFA_OFFSET ORIG_RAX-ARGOFFSET+8 + /* reserve pt_regs for scratch regs and rbp */ + subq $ORIG_RAX-RBP, %rsp + CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP call save_args PARTIAL_FRAME 0 call \func @@ -808,9 +813,14 @@ ret_from_intr: TRACE_IRQS_OFF decl PER_CPU_VAR(irq_count) leaveq + CFI_RESTORE rbp CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET -8 + + /* we did not save rbx, restore only from ARGOFFSET */ + addq $8, %rsp + CFI_ADJUST_CFA_OFFSET -8 exit_intr: GET_THREAD_INFO(%rcx) testl $3,CS-ARGOFFSET(%rsp) -- 2.20.1