Messages in this thread Patch in this message | | | Date | Tue, 12 Aug 2014 11:31:07 +0200 | From | Denys Vlasenko <> | Subject | Re: [PATCH 4/5] x86: entry_64.S: always allocate complete "struct pt_regs" |
| |
On 08/11/2014 05:13 PM, H. Peter Anvin wrote: > On 08/11/2014 08:08 AM, Jan Beulich wrote: >>> No, in *human language*. What does the DW_CFA_def_cfa_expression >>> actually aim to accomplish? If you don't know the innards of the DWARF >>> spec, the whole thing might as well be Hungarian. >> >> Just like the other DW_CFA_def_cfa_* ones it sets the current >> frame address (CFA), just not via one of the pre-canned shortcuts, >> but via an expression (in the case here de-referencing the stack >> pointer to read the top of stack, and then adding the necessary >> offset). So it indeed is similar enough to other .cfi_* annotations we >> use without further comments. >> > > Actually, what you had inside the parenteses there is actually a > half-decent comment. I'm going to pretend the rest of this wasn't posted.
Jan, Pater, does this look correct _and_ human-understandable?
--- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -652,10 +652,14 @@ END(interrupt) cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp CFI_DEF_CFA_REGISTER rsi pushq %rsi + /* + * For debugger: + * "CFA (Current Frame Address) is the value on stack + offset" + */ CFI_ESCAPE 0x0f /* DW_CFA_def_cfa_expression */, 6, \ - 0x77 /* DW_OP_breg7 */, 0, \ + 0x77 /* DW_OP_breg7 (rsp) */, 0, \ 0x06 /* DW_OP_deref */, \ - 0x08 /* DW_OP_const1u */, SS+8-RBP, \ + 0x08 /* DW_OP_const1u */, SIZEOF_PTREGS-RBP, \ 0x22 /* DW_OP_plus */ /* We entered an interrupt context - irqs are off: */ TRACE_IRQS_OFF
| |