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perf dwarf-aux: Add die_get_cfa()

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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.

Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20240117062657.985479-8-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Namhyung Kim 2024-01-16 22:26:55 -08:00
parent 5f7cdde843
commit 6fed025f11
2 changed files with 82 additions and 1 deletions
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68
tools/perf/util/dwarf-aux.c
View File

@ -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

15
tools/perf/util/dwarf-aux.h
View File

@ -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 */