The die_get_cfa() is to get frame base register and offset at the given
instruction address (pc). This info will be used to locate stack
variables which have location expression using DW_OP_fbreg.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/dwarf-aux.c | 68 ++++++++++++++++++++++++++++++++++++-
tools/perf/util/dwarf-aux.h | 15 ++++++++
2 files changed, 82 insertions(+), 1 deletion(-)
@@ -1407,7 +1407,73 @@ Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr pc,
*offset = data.offset;
return result;
}
-#endif
+#endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
+
+#ifdef HAVE_DWARF_CFI_SUPPORT
+static int reg_from_dwarf_op(Dwarf_Op *op)
+{
+ switch (op->atom) {
+ case DW_OP_reg0 ... DW_OP_reg31:
+ return op->atom - DW_OP_reg0;
+ case DW_OP_breg0 ... DW_OP_breg31:
+ return op->atom - DW_OP_breg0;
+ case DW_OP_regx:
+ case DW_OP_bregx:
+ return op->number;
+ default:
+ break;
+ }
+ return -1;
+}
+
+static int offset_from_dwarf_op(Dwarf_Op *op)
+{
+ switch (op->atom) {
+ case DW_OP_reg0 ... DW_OP_reg31:
+ case DW_OP_regx:
+ return 0;
+ case DW_OP_breg0 ... DW_OP_breg31:
+ return op->number;
+ case DW_OP_bregx:
+ return op->number2;
+ default:
+ break;
+ }
+ return -1;
+}
+
+/**
+ * die_get_cfa - Get frame base information
+ * @dwarf: a Dwarf info
+ * @pc: program address
+ * @preg: pointer for saved register
+ * @poffset: pointer for saved offset
+ *
+ * This function gets register and offset for CFA (Canonical Frame Address)
+ * by searching the CIE/FDE info. The CFA usually points to the start address
+ * of the current stack frame and local variables can be located using an offset
+ * from the CFA. The @preg and @poffset will be updated if it returns 0.
+ */
+int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset)
+{
+ Dwarf_CFI *cfi;
+ Dwarf_Frame *frame = NULL;
+ Dwarf_Op *ops = NULL;
+ size_t nops;
+
+ cfi = dwarf_getcfi(dwarf);
+ if (cfi == NULL)
+ return -1;
+
+ if (!dwarf_cfi_addrframe(cfi, pc, &frame) &&
+ !dwarf_frame_cfa(frame, &ops, &nops) && nops == 1) {
+ *preg = reg_from_dwarf_op(ops);
+ *poffset = offset_from_dwarf_op(ops);
+ return 0;
+ }
+ return -1;
+}
+#endif /* HAVE_DWARF_CFI_SUPPORT */
/*
* die_has_loclist - Check if DW_AT_location of @vr_die is a location list
@@ -177,4 +177,19 @@ static inline Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die __maybe_unu
#endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
+#ifdef HAVE_DWARF_CFI_SUPPORT
+
+/* Get the frame base information from CFA */
+int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset);
+
+#else /* HAVE_DWARF_CFI_SUPPORT */
+
+static inline int die_get_cfa(Dwarf *dwarf __maybe_unused, u64 pc __maybe_unused,
+ int *preg __maybe_unused, int *poffset __maybe_unused)
+{
+ return -1;
+}
+
+#endif /* HAVE_DWARF_CFI_SUPPORT */
+
#endif /* _DWARF_AUX_H */