Commit-ID: e4754e9a25ce70ee45e89a9c916ac69a2fc2d44e
Gitweb: http://git.kernel.org/tip/e4754e9a25ce70ee45e89a9c916ac69a2fc2d44e
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Thu, 6 Jan 2011 15:22:47 +0100
Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CommitDate: Thu, 6 Jan 2011 15:22:47 +0100
x86: Fix rbp saving in pt_regs on irq entry
>From the x86_64 low level interrupt handlers, the frame pointer is
saved in pt_regs in the wrong place, in the offset of rbx.
rbx is not part of the irq partial saved registers, so it's not
critical, but later code that uses get_irq_regs() to get the
interrupted frame pointer instead get a stale rbx value, causing
unwinding code to fail miserably.
One noticeable impact is the breakage of the stack unwinding from
perf software clock events (cpu-clock, task-clock).
This patch simply fixes up the saving of rbp to be in pt_regs::rbp
instead of pt_regs::rbx
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
Reported-by: Soeren Sandmann Pedersen <sandmann@xxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
---
arch/x86/kernel/entry_64.S | 31 +++++++++++++++++++------------
1 files changed, 19 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e3ba417..fc3cac6 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)
@@ -782,7 +786,8 @@ END(interrupt)
/* 0(%rsp): ~(interrupt number) */
.macro interrupt func
- subq $ORIG_RAX-ARGOFFSET+8, %rsp
+ /* reserve pt_regs for scratch regs and rbp */
+ subq $ORIG_RAX-RBP, %rsp
CFI_ADJUST_CFA_OFFSET ORIG_RAX-ARGOFFSET+8
call save_args
PARTIAL_FRAME 0
@@ -808,6 +813,8 @@ ret_from_intr:
TRACE_IRQS_OFF
decl PER_CPU_VAR(irq_count)
leaveq
+ /* we did not save rbx, restore only from ARGOFFSET */
+ addq $8, %rsp
CFI_RESTORE rbp
CFI_DEF_CFA_REGISTER rsp
CFI_ADJUST_CFA_OFFSET -8
--
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