Despite -fno-omit-frame-pointer the compiler may omit the frame pointer,
often for relatively simple leaf functions. (To give a specific example,
the case I've run into this with is _pci_hide_device() and gcc 8.
Interestingly the even more simple neighboring iommu_has_feature() does
get a frame pointer set up, around just a single instruction. But this
may be a result of the size-of-asm() effects discussed elsewhere.)
Log the top-of-stack value if it looks valid _or_ if RIP looks invalid.
Also annotate all stack trace entries with a marker, to indicate their
origin:
R: register state
F: frame pointer based
S: raw stack contents
Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
v3: Tag stack entries consistently, but differently than in v2.
v2: Re-base over changes to earlier patch.
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -433,7 +433,7 @@ static void _show_trace(unsigned long sp
{
addr = *stack++;
if ( is_active_kernel_text(addr) )
- printk(" [<%p>] %pS\n", _p(addr), _p(addr));
+ printk(" [<%p>] S %pS\n", _p(addr), _p(addr));
}
}
@@ -476,7 +476,7 @@ static void _show_trace(unsigned long sp
addr = frame[1];
}
- printk(" [<%p>] %pS\n", _p(addr), _p(addr));
+ printk(" [<%p>] F %pS\n", _p(addr), _p(addr));
low = (unsigned long)&frame[2];
}
@@ -505,21 +505,26 @@ static void show_trace(const struct cpu_
*/
if ( is_active_kernel_text(regs->rip) ||
!is_active_kernel_text(tos) )
- printk(" [<%p>] %pS\n", _p(regs->rip), _p(regs->rip));
- else if ( fault )
+ printk(" [<%p>] R %pS\n", _p(regs->rip), _p(regs->rip));
+
+ if ( fault )
{
printk(" [Fault on access]\n");
return;
}
+
/*
- * Else RIP looks bad but the top of the stack looks good. Perhaps we
- * followed a wild function pointer? Lets assume the top of the stack is a
+ * If RIP looks bad or the top of the stack looks good, log the top of
+ * stack as well. Perhaps we followed a wild function pointer, or we're
+ * in a function without frame pointer, or in a function prologue before
+ * the frame pointer gets set up? Let's assume the top of the stack is a
* return address; print it and skip past so _show_trace() doesn't print
* it again.
*/
- else
+ if ( !is_active_kernel_text(regs->rip) ||
+ is_active_kernel_text(tos) )
{
- printk(" [<%p>] %pS\n", _p(tos), _p(tos));
+ printk(" [<%p>] S %pS\n", _p(tos), _p(tos));
sp++;
}
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