[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 2/2] x86/traps: widen condition for logging top-of-stack
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 non-frame-pointer-based stack trace entries with a question mark, to signal clearly that any one of them may not actually be part of the call stack. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -431,7 +431,7 @@ 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>] ? %pS\n", _p(addr), _p(addr)); } } @@ -502,21 +502,25 @@ 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)); + + if ( !sp ) + 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? Lets 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 ( sp ) + if ( !is_active_kernel_text(regs->rip) || + is_active_kernel_text(tos) ) { - printk(" [<%p>] %pS\n", _p(tos), _p(tos)); + printk(" [<%p>] ? %pS\n", _p(tos), _p(tos)); sp++; } - if ( !sp ) - return; - _show_trace((unsigned long)sp, regs->rbp); printk("\n"); _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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