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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 2/2] Xen/x86: Improve information from domain_crash_synchronous
As it currently stands, the string "domain_crash_sync called from entry.S" is
not helpful at identifying why the domain was crashed, and a debug build of
Xen doesn't help the matter
This patch improves the information printed, by pointing to where the crash
decision was made.
Specific improvements include:
* Moving the ascii string "domain_crash_sync called from entry.S\n" away from
some semi-hot code cache lines.
* Moving the printk into C code (especially as this_cpu() is miserable to use
in assembly code)
* Undo the previous confusing situation of having the
domain_crash_synchronous() as a macro in C code, yet a global symbol in
assembly code.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
Changes in v2:
* Remove incorrect .globl's for {compat_,}create_bounce_frame
* Tweak printed string format
* Introduce and use UNLIKELY_ENTRY_LABEL() to save open-coding it
* Use __UNLIKELY_END() now it is available
* Remove redundant ud2's from the unlikely codepath - being preceded by a
jmp rather than a call, there was no way they could actually be executed
---
xen/arch/x86/traps.c | 12 +++++++++
xen/arch/x86/x86_64/compat/entry.S | 11 ++++++---
xen/arch/x86/x86_64/entry.S | 48 ++++++++++++++++++------------------
xen/include/asm-x86/asm_defns.h | 4 +++
xen/include/xen/sched.h | 7 ++++++
5 files changed, 54 insertions(+), 28 deletions(-)
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 50fb6ba..bc0d513 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -3748,6 +3748,18 @@ unsigned long do_get_debugreg(int reg)
return -EINVAL;
}
+void asm_domain_crash_synchronous(unsigned long addr)
+{
+ if ( addr == 0 )
+ addr = this_cpu(last_extable_addr);
+
+ printk("domain_crash_sync called from entry.S\n"
+ " fault at %p: ", _p(addr));
+ print_symbol("%s\n", addr);
+
+ __domain_crash_synchronous();
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/x86/x86_64/compat/entry.S
b/xen/arch/x86/x86_64/compat/entry.S
index c0afe2c..4ec1df7 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -329,7 +329,10 @@ UNLIKELY_END(compat_bounce_failsafe)
movzwl TRAPBOUNCE_cs(%rdx),%eax
/* Null selectors (0-3) are not allowed. */
testl $~3,%eax
- jz domain_crash_synchronous
+UNLIKELY_START(z, compat_bounce_null_selector)
+ lea UNLIKELY_ENTRY_LABEL(compat_bounce_null_selector)(%rip), %rdi
+ jmp asm_domain_crash_synchronous /* Does not return */
+__UNLIKELY_END(compat_bounce_null_selector)
movl %eax,UREGS_cs+8(%rsp)
movl TRAPBOUNCE_eip(%rdx),%eax
movl %eax,UREGS_rip+8(%rsp)
@@ -339,10 +342,10 @@ UNLIKELY_END(compat_bounce_failsafe)
xorl %edi,%edi
jmp .Lft13
.previous
- _ASM_EXTABLE(.Lft1, domain_crash_synchronous)
+ _ASM_EXTABLE(.Lft1, dom_crash_sync_extable)
_ASM_EXTABLE(.Lft2, compat_crash_page_fault)
_ASM_EXTABLE(.Lft3, compat_crash_page_fault_4)
- _ASM_EXTABLE(.Lft4, domain_crash_synchronous)
+ _ASM_EXTABLE(.Lft4, dom_crash_sync_extable)
_ASM_EXTABLE(.Lft5, compat_crash_page_fault_4)
_ASM_EXTABLE(.Lft6, compat_crash_page_fault_8)
_ASM_EXTABLE(.Lft7, compat_crash_page_fault)
@@ -363,7 +366,7 @@ compat_crash_page_fault:
.Lft14: mov %edi,%fs
movl %esi,%edi
call show_page_walk
- jmp domain_crash_synchronous
+ jmp dom_crash_sync_extable
.section .fixup,"ax"
.Lfx14:
xorl %edi,%edi
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index f64e871..d44a6c1 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -370,7 +370,10 @@ create_bounce_frame:
sbb %ecx,%ecx # In +ve address space? Then okay.
cmpq %rax,%rsi
adc %ecx,%ecx # Above Xen private area? Then okay.
- jg domain_crash_synchronous
+UNLIKELY_START(g, create_bounce_frame_bad_sp)
+ lea UNLIKELY_ENTRY_LABEL(create_bounce_frame_bad_sp)(%rip), %rdi
+ jmp asm_domain_crash_synchronous /* Does not return */
+__UNLIKELY_END(create_bounce_frame_bad_sp)
movb TRAPBOUNCE_flags(%rdx),%cl
subq $40,%rsi
movq UREGS_ss+8(%rsp),%rax
@@ -429,26 +432,26 @@ UNLIKELY_END(bounce_failsafe)
movq $FLAT_KERNEL_CS,UREGS_cs+8(%rsp)
movq TRAPBOUNCE_eip(%rdx),%rax
testq %rax,%rax
- jz domain_crash_synchronous
+UNLIKELY_START(z, create_bounce_frame_bad_bounce_ip)
+ lea UNLIKELY_ENTRY_LABEL(create_bounce_frame_bad_bounce_ip)(%rip),
%rdi
+ jmp asm_domain_crash_synchronous /* Does not return */
+__UNLIKELY_END(create_bounce_frame_bad_bounce_ip)
movq %rax,UREGS_rip+8(%rsp)
ret
- _ASM_EXTABLE(.Lft2, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft3, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft4, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft5, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft6, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft7, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft8, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft9, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft10, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft11, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft12, domain_crash_synchronous)
- _ASM_EXTABLE(.Lft13, domain_crash_synchronous)
-
-domain_crash_synchronous_string:
- .asciz "domain_crash_sync called from entry.S\n"
-
-ENTRY(domain_crash_synchronous)
+ _ASM_EXTABLE(.Lft2, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft3, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft4, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft5, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft6, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft7, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft8, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft9, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft10, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft11, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft12, dom_crash_sync_extable)
+ _ASM_EXTABLE(.Lft13, dom_crash_sync_extable)
+
+ENTRY(dom_crash_sync_extable)
# Get out of the guest-save area of the stack.
GET_STACK_BASE(%rax)
leaq STACK_CPUINFO_FIELD(guest_cpu_user_regs)(%rax),%rsp
@@ -459,11 +462,8 @@ ENTRY(domain_crash_synchronous)
setz %al
leal (%rax,%rax,2),%eax
orb %al,UREGS_cs(%rsp)
- # printk(domain_crash_synchronous_string)
- leaq domain_crash_synchronous_string(%rip),%rdi
- xorl %eax,%eax
- call printk
- jmp __domain_crash_synchronous
+ xorl %edi,%edi
+ jmp asm_domain_crash_synchronous /* Does not return */
/* No special register assumptions. */
ENTRY(ret_from_intr)
diff --git a/xen/include/asm-x86/asm_defns.h b/xen/include/asm-x86/asm_defns.h
index 25032d5..34034f3 100644
--- a/xen/include/asm-x86/asm_defns.h
+++ b/xen/include/asm-x86/asm_defns.h
@@ -35,10 +35,14 @@ void ret_from_intr(void);
#ifdef __ASSEMBLY__
#define UNLIKELY_START(cond, tag) \
+ .Lunlikely.entry.tag: \
j##cond .Lunlikely.tag; \
.subsection 1; \
.Lunlikely.tag:
+#define UNLIKELY_ENTRY_LABEL(tag) \
+ .Lunlikely.entry.tag
+
#define UNLIKELY_DONE(cond, tag) \
j##cond .Llikely.tag
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index ae6a3b8..8e66d6b 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -541,6 +541,13 @@ void __domain_crash_synchronous(void)
__attribute__((noreturn));
__domain_crash_synchronous(); \
} while (0)
+/*
+ * Called from assembly code, with an optional address to help indicate why
+ * the crash occured. If addr is 0, look up address from last extable
+ * redirection.
+ */
+void asm_domain_crash_synchronous(unsigned long addr)
__attribute__((noreturn));
+
#define set_current_state(_s) do { current->state = (_s); } while (0)
void scheduler_init(void);
int sched_init_vcpu(struct vcpu *v, unsigned int processor);
--
1.7.10.4
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