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[Libunwind-devel] [PATCH] Implement DWARF DW_CFA_val_expression for x86_
From: |
Tim Deegan |
Subject: |
[Libunwind-devel] [PATCH] Implement DWARF DW_CFA_val_expression for x86_64 |
Date: |
Mon, 20 Jan 2014 12:41:29 +0100 |
User-agent: |
Mutt/1.5.22 (2013-10-16) |
Ubuntu's libc-bin (2.15-0ubuntu20.2) on x86_64 uses DW_CFA_val_expression
in describing the pthread spinlock operations __lll_unlock_wake() and
__lll_lock_wait(). libunwind 1.1 doesn't understand that opcode and
so backtraces from those operations are truncated.
This changeset adds basic support for it, by adding a new type to
dwarf_loc_t that describes the register's actual contents rather than
its location. I've only implemented the new type for x86_64, and
stubbed it out for all other architectures -- it looks like a lot
of that code is duplicated so oughtn't to be that hard, but I don't
have test cases for them.
Tested that DW_CFA_val_expression works on x86_64 (by using
https://code.google.com/p/gperftools/ on a lock-heavy program).
Build-tested on x86, x86_64 and arm. The unit tests don't pass for me
on any of those archs, but this cset doesn't break anything that was
passing before.
Signed-off-by: Tim Deegan <address@hidden>
---
include/dwarf.h | 2 ++
include/libunwind_i.h | 5 +++++
include/tdep-x86_64/libunwind_i.h | 18 ++++++++++++++++--
src/dwarf/Gparser.c | 29 ++++++++++++++++++++++++++---
4 files changed, 49 insertions(+), 5 deletions(-)
diff --git a/include/dwarf.h b/include/dwarf.h
index 7800567..fba91f9 100644
--- a/include/dwarf.h
+++ b/include/dwarf.h
@@ -165,6 +165,7 @@ typedef enum
DW_CFA_offset_extended_sf = 0x11,
DW_CFA_def_cfa_sf = 0x12,
DW_CFA_def_cfa_offset_sf = 0x13,
+ DW_CFA_val_expression = 0x16,
DW_CFA_lo_user = 0x1c,
DW_CFA_MIPS_advance_loc8 = 0x1d,
DW_CFA_GNU_window_save = 0x2d,
@@ -224,6 +225,7 @@ typedef enum
DWARF_WHERE_CFAREL, /* register saved at CFA-relative
address */
DWARF_WHERE_REG, /* register saved in another register */
DWARF_WHERE_EXPR, /* register saved */
+ DWARF_WHERE_EXPR_VAL, /* register has computed value */
}
dwarf_where_t;
diff --git a/include/libunwind_i.h b/include/libunwind_i.h
index 0be551f..892e39c 100644
--- a/include/libunwind_i.h
+++ b/include/libunwind_i.h
@@ -351,6 +351,11 @@ static inline void invalidate_edi (struct elf_dyn_info
*edi)
# define tdep_get_func_addr(as,addr,v) (*(v) = addr, 0)
#endif
+#ifndef DWARF_VAL_LOC
+# define DWARF_IS_VAL_LOC(l) 0
+# define DWARF_VAL_LOC(c,v) DWARF_NULL_LOC
+#endif
+
#define UNW_ALIGN(x,a) (((x)+(a)-1UL)&~((a)-1UL))
#endif /* libunwind_i_h */
diff --git a/include/tdep-x86_64/libunwind_i.h
b/include/tdep-x86_64/libunwind_i.h
index 8c9cd05..23da05d 100644
--- a/include/tdep-x86_64/libunwind_i.h
+++ b/include/tdep-x86_64/libunwind_i.h
@@ -109,25 +109,33 @@ dwarf_get_uc(const struct dwarf_cursor *cursor)
# define DWARF_IS_NULL_LOC(l) (DWARF_GET_LOC (l) == 0)
# define DWARF_LOC(r, t) ((dwarf_loc_t) { .val = (r) })
# define DWARF_IS_REG_LOC(l) 0
+# define DWARF_IS_MEM_LOC(l) 1
+# define DWARF_IS_VAL_LOC(l) 0
# define DWARF_REG_LOC(c,r) (DWARF_LOC((unw_word_t) \
x86_64_r_uc_addr(dwarf_get_uc(c), (r)), 0))
# define DWARF_MEM_LOC(c,m) DWARF_LOC ((m), 0)
# define DWARF_FPREG_LOC(c,r) (DWARF_LOC((unw_word_t) \
x86_64_r_uc_addr(dwarf_get_uc(c), (r)), 0))
+# define DWARF_VAL_LOC(c,v) DWARF_NULL_LOC
+
#else /* !UNW_LOCAL_ONLY */
# define DWARF_LOC_TYPE_FP (1 << 0)
# define DWARF_LOC_TYPE_REG (1 << 1)
+# define DWARF_LOC_TYPE_VAL (1 << 2)
# define DWARF_NULL_LOC DWARF_LOC (0, 0)
# define DWARF_IS_NULL_LOC(l) \
({ dwarf_loc_t _l = (l); _l.val == 0 && _l.type == 0; })
# define DWARF_LOC(r, t) ((dwarf_loc_t) { .val = (r), .type = (t) })
# define DWARF_IS_REG_LOC(l) (((l).type & DWARF_LOC_TYPE_REG) != 0)
# define DWARF_IS_FP_LOC(l) (((l).type & DWARF_LOC_TYPE_FP) != 0)
+# define DWARF_IS_MEM_LOC(l) ((l).type == 0)
+# define DWARF_IS_VAL_LOC(l) (((l).type & DWARF_LOC_TYPE_VAL) != 0)
# define DWARF_REG_LOC(c,r) DWARF_LOC((r), DWARF_LOC_TYPE_REG)
# define DWARF_MEM_LOC(c,m) DWARF_LOC ((m), 0)
# define DWARF_FPREG_LOC(c,r) DWARF_LOC((r), (DWARF_LOC_TYPE_REG \
| DWARF_LOC_TYPE_FP))
+# define DWARF_VAL_LOC(c,v) DWARF_LOC ((v), DWARF_LOC_TYPE_VAL)
#endif /* !UNW_LOCAL_ONLY */
@@ -158,9 +166,12 @@ dwarf_get (struct dwarf_cursor *c, dwarf_loc_t loc,
unw_word_t *val)
if (DWARF_IS_REG_LOC (loc))
return (*c->as->acc.access_reg) (c->as, DWARF_GET_LOC (loc), val,
0, c->as_arg);
- else
+ if (DWARF_IS_MEM_LOC (loc))
return (*c->as->acc.access_mem) (c->as, DWARF_GET_LOC (loc), val,
0, c->as_arg);
+ assert(DWARF_IS_VAL_LOC (loc));
+ *val = DWARF_GET_LOC (loc);
+ return 0;
}
static inline int
@@ -172,9 +183,12 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc,
unw_word_t val)
if (DWARF_IS_REG_LOC (loc))
return (*c->as->acc.access_reg) (c->as, DWARF_GET_LOC (loc), &val,
1, c->as_arg);
- else
+ if (DWARF_IS_MEM_LOC (loc))
return (*c->as->acc.access_mem) (c->as, DWARF_GET_LOC (loc), &val,
1, c->as_arg);
+ assert(DWARF_IS_VAL_LOC (loc));
+ loc = DWARF_VAL_LOC(c, val);
+ return 0;
}
#define tdep_getcontext_trace UNW_ARCH_OBJ(getcontext_trace)
diff --git a/src/dwarf/Gparser.c b/src/dwarf/Gparser.c
index b251e31..82a6129 100644
--- a/src/dwarf/Gparser.c
+++ b/src/dwarf/Gparser.c
@@ -334,6 +334,21 @@ run_cfi_program (struct dwarf_cursor *c,
dwarf_state_record_t *sr,
*addr += len;
break;
+ case DW_CFA_val_expression:
+ if ((ret = read_regnum (as, a, addr, ®num, arg)) < 0)
+ goto fail;
+
+ /* Save the address of the DW_FORM_block for later evaluation. */
+ set_reg (sr, regnum, DWARF_WHERE_EXPR_VAL, *addr);
+
+ if ((ret = dwarf_read_uleb128 (as, a, addr, &len, arg)) < 0)
+ goto fail;
+
+ Debug (15, "CFA_val_expression r%lu @ 0x%lx [%lu bytes]\n",
+ (long) regnum, (long) addr, (long) len);
+ *addr += len;
+ break;
+
case DW_CFA_GNU_args_size:
if ((ret = dwarf_read_uleb128 (as, a, addr, &val, arg)) < 0)
goto fail;
@@ -685,7 +700,7 @@ create_state_record_for (struct dwarf_cursor *c,
dwarf_state_record_t *sr,
static inline int
eval_location_expr (struct dwarf_cursor *c, unw_addr_space_t as,
unw_accessors_t *a, unw_word_t addr,
- dwarf_loc_t *locp, void *arg)
+ dwarf_loc_t *locp, void *arg, int is_val)
{
int ret, is_register;
unw_word_t len, val;
@@ -700,6 +715,8 @@ eval_location_expr (struct dwarf_cursor *c,
unw_addr_space_t as,
if (is_register)
*locp = DWARF_REG_LOC (c, dwarf_to_unw_regnum (val));
+ else if (is_val)
+ *locp = DWARF_VAL_LOC (c, val);
else
*locp = DWARF_MEM_LOC (c, val);
@@ -753,7 +770,7 @@ apply_reg_state (struct dwarf_cursor *c, struct
dwarf_reg_state *rs)
assert (rs->reg[DWARF_CFA_REG_COLUMN].where == DWARF_WHERE_EXPR);
addr = rs->reg[DWARF_CFA_REG_COLUMN].val;
- if ((ret = eval_location_expr (c, as, a, addr, &cfa_loc, arg)) < 0)
+ if ((ret = eval_location_expr (c, as, a, addr, &cfa_loc, arg, 0)) < 0)
return ret;
/* the returned location better be a memory location... */
if (DWARF_IS_REG_LOC (cfa_loc))
@@ -782,7 +799,13 @@ apply_reg_state (struct dwarf_cursor *c, struct
dwarf_reg_state *rs)
case DWARF_WHERE_EXPR:
addr = rs->reg[i].val;
- if ((ret = eval_location_expr (c, as, a, addr, c->loc + i, arg)) < 0)
+ if ((ret = eval_location_expr (c, as, a, addr, c->loc + i, arg, 0)) <
0)
+ return ret;
+ break;
+
+ case DWARF_WHERE_EXPR_VAL:
+ addr = rs->reg[i].val;
+ if ((ret = eval_location_expr (c, as, a, addr, c->loc + i, arg, 1)) <
0)
return ret;
break;
}
--
1.8.3.2
- [Libunwind-devel] [PATCH] Implement DWARF DW_CFA_val_expression for x86_64,
Tim Deegan <=