[PATCH v3][Binutils][GAS] arm: Use DWARF numbering convention for pseudo-register representation
Victor Do Nascimento
victor.donascimento@arm.com
Fri Jul 29 15:40:49 GMT 2022
Hi all,
This patch modifies the internal `struct reg_entry' numbering of DWARF
pseudo-registers to match values assigned in DWARF standards (see "4.1
DWARF register names" in [1]) and amends the unwinder .save
directive-processing code to correctly handle mixed register-type save
directives.
The mechanism for splitting the register list is re-written to comply
with register ordering on push statements, being that registers are
stored on the stack in numerical order, with the lowest numbered
register at the lowest address [2].
Consequently, the parsing of the hypothetical directive
.save{r4-r7, r10, ra_auth_core, lr}
has been changed such as rather than producing
.save{r4-r7, r10}
.save{ra_auth_code}
.save{lr}
as was the case with previous implementation, now produces:
.save{lr}
.save{ra_auth_code}
.save{r4-r7, r10}
Tested for arm-none-eabi on x86_64 and aarch64 hosts.
Best regards,
Victor
[1] <https://github.com/ARM-software/abi-aa/blob/main/aadwarf32/aadwarf32.rst>
[2] <https://developer.arm.com/documentation/dui0473/j/arm-and-thumb-instructions/push>
gas/Changelog:
* config/tc-arm.c (REG_RA_AUTH_CODE): New.
(parse_dot_save): Likewise.
(parse_reg_list): Remove obsolete code.
(reg_names): Set ra_auth_code to 143.
(s_arm_unwind_save): Handle core and pseudo-register lists via
parse_dot_save.
(s_arm_unwind_save_mixed): Deleted.
(s_arm_unwind_save_pseudo): Handle one register at a time.
* testsuite/gas/arm/unwind-pacbti-m-readelf.d: Fix test.
* testsuite/gas/arm/unwind-pacbti-m.d: Likewise.
---
gas/config/tc-arm.c | 160 ++++++++++--------
.../gas/arm/unwind-pacbti-m-readelf.d | 4 +-
gas/testsuite/gas/arm/unwind-pacbti-m.d | 2 +-
3 files changed, 96 insertions(+), 70 deletions(-)
diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index 2e6d175482e..f2e7f73cc2d 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -742,6 +742,7 @@ const char * const reg_expected_msgs[] =
#define REG_SP 13
#define REG_LR 14
#define REG_PC 15
+#define REG_RA_AUTH_CODE 143
/* ARM instructions take 4bytes in the object file, Thumb instructions
take 2: */
@@ -1943,21 +1944,6 @@ parse_reg_list (char ** strp, enum reg_list_els etype)
reg = arm_reg_parse (&str, rt);
- /* Skip over allowed registers of alternative types in mixed-type
- register lists. */
- if (reg == FAIL && rt == REG_TYPE_PSEUDO
- && ((reg = arm_reg_parse (&str, REG_TYPE_RN)) != FAIL))
- {
- cur_reg = reg;
- continue;
- }
- else if (reg == FAIL && rt == REG_TYPE_RN
- && ((reg = arm_reg_parse (&str, REG_TYPE_PSEUDO)) != FAIL))
- {
- cur_reg = reg;
- continue;
- }
-
if (etype == REGLIST_CLRM)
{
if (reg == REG_SP || reg == REG_PC)
@@ -4139,7 +4125,6 @@ s_arm_unwind_fnstart (int ignored ATTRIBUTE_UNUSED)
unwind.sp_restored = 0;
}
-
/* Parse a handlerdata directive. Creates the exception handling table entry
for the function. */
@@ -4297,15 +4282,19 @@ s_arm_unwind_personality (int ignored ATTRIBUTE_UNUSED)
/* Parse a directive saving pseudo registers. */
static void
-s_arm_unwind_save_pseudo (long range)
+s_arm_unwind_save_pseudo (int regno)
{
valueT op;
- if (range & (1 << 12))
+ switch (regno)
{
+ case REG_RA_AUTH_CODE:
/* Opcode for restoring RA_AUTH_CODE. */
op = 0xb4;
add_unwind_opcode (op, 1);
+ break;
+ default:
+ as_bad (_("Unknown register no. encountered: %d\n"), regno);
}
}
@@ -4375,6 +4364,81 @@ s_arm_unwind_save_core (long range)
}
}
+/* Implement correct handling of .save lists enabling the split into
+sublists where necessary, while preserving correct sublist ordering. */
+
+static void
+parse_dot_save (char **str_p, int prev_reg)
+{
+ long core_regs = 0;
+ int reg;
+ int in_range = 0;
+
+ if (**str_p == ',')
+ *str_p += 1;
+ if (**str_p == '}')
+ {
+ *str_p += 1;
+ return;
+ }
+
+ while ((reg = arm_reg_parse (str_p, REG_TYPE_RN)) != FAIL)
+ {
+ if (!in_range)
+ {
+ if (core_regs & (1 << reg))
+ as_tsktsk (_("Warning: duplicated register (r%d) in register list"),
+ reg);
+ else if (reg <= prev_reg)
+ as_tsktsk (_("Warning: register list not in ascending order"));
+
+ core_regs |= (1 << reg);
+ prev_reg = reg;
+ if (skip_past_char (str_p, '-') != FAIL)
+ in_range = 1;
+ else if (skip_past_comma (str_p) == FAIL)
+ first_error (_("bad register list"));
+ }
+ else
+ {
+ int i;
+ if (reg <= prev_reg)
+ first_error (_("bad range in register list"));
+ for (i = prev_reg + 1; i <= reg; i++)
+ {
+ if (core_regs & (1 << i))
+ as_tsktsk (_("Warning: duplicated register (r%d) in register list"),
+ i);
+ else
+ core_regs |= 1 << i;
+ }
+ in_range = 0;
+ }
+ }
+ if (core_regs)
+ {
+ /* Higher register numbers go in higher memory addresses. When splitting
+ a list, right-most sublist should therefore be .saved first: use
+ recursion for this. */
+ parse_dot_save (str_p, reg);
+ /* We're back from recursion, so emit .save insn for sublist. */
+ s_arm_unwind_save_core (core_regs);
+ return;
+ }
+ /* Handle pseudo-regs, under assumption these are emitted singly. */
+ else if ((reg = arm_reg_parse (str_p, REG_TYPE_PSEUDO)) != FAIL)
+ {
+ /* Recurse for remainder of input. Note: No assumption is made regarding
+ which register in core register set holds pseudo-register, thus it's
+ not considered in ordering check beyond ensuring it's not sandwiched
+ between 2 consecutive registers. */
+ parse_dot_save (str_p, prev_reg + 1);
+ s_arm_unwind_save_pseudo (reg);
+ return;
+ }
+ else
+ as_bad (BAD_SYNTAX);
+}
/* Parse a directive saving FPA registers. */
@@ -4716,39 +4780,13 @@ s_arm_unwind_save_mmxwcg (void)
ignore_rest_of_line ();
}
-/* Convert range and mask_range into a sequence of s_arm_unwind_core
- and s_arm_unwind_pseudo operations. We assume that mask_range will
- not have consecutive bits set, or that one operation per bit is
- acceptable. */
-
-static void
-s_arm_unwind_save_mixed (long range, long mask_range)
-{
- while (mask_range)
- {
- long mask_bit = mask_range & -mask_range;
- long subrange = range & (mask_bit - 1);
-
- if (subrange)
- s_arm_unwind_save_core (subrange);
-
- s_arm_unwind_save_pseudo (mask_bit);
- range &= ~subrange;
- mask_range &= ~mask_bit;
- }
-
- if (range)
- s_arm_unwind_save_core (range);
-}
-
/* Parse an unwind_save directive.
If the argument is non-zero, this is a .vsave directive. */
static void
s_arm_unwind_save (int arch_v6)
{
- char *peek, *mask_peek;
- long range, mask_range;
+ char *peek;
struct reg_entry *reg;
bool had_brace = false;
@@ -4756,7 +4794,7 @@ s_arm_unwind_save (int arch_v6)
as_bad (MISSING_FNSTART);
/* Figure out what sort of save we have. */
- peek = mask_peek = input_line_pointer;
+ peek = input_line_pointer;
if (*peek == '{')
{
@@ -4788,20 +4826,13 @@ s_arm_unwind_save (int arch_v6)
case REG_TYPE_PSEUDO:
case REG_TYPE_RN:
- mask_range = parse_reg_list (&mask_peek, REGLIST_PSEUDO);
- range = parse_reg_list (&input_line_pointer, REGLIST_RN);
-
- if (range == FAIL || mask_range == FAIL)
- {
- as_bad (_("expected register list"));
- ignore_rest_of_line ();
- return;
- }
-
- demand_empty_rest_of_line ();
-
- s_arm_unwind_save_mixed (range, mask_range);
- return;
+ {
+ if (had_brace)
+ input_line_pointer++;
+ parse_dot_save (&input_line_pointer, -1);
+ demand_empty_rest_of_line ();
+ return;
+ }
case REG_TYPE_VFD:
if (arch_v6)
@@ -23993,12 +24024,8 @@ static const struct reg_entry reg_names[] =
/* XScale accumulator registers. */
REGNUM(acc,0,XSCALE), REGNUM(ACC,0,XSCALE),
- /* DWARF ABI defines RA_AUTH_CODE to 143. It also reserves 134-142 for future
- expansion. RA_AUTH_CODE here is given the value 143 % 134 to make it easy
- for tc_arm_regname_to_dw2regnum to translate to DWARF reg number using
- 134 + reg_number should the range 134 to 142 be used for more pseudo regs
- in the future. This also helps fit RA_AUTH_CODE into a bitmask. */
- REGDEF(ra_auth_code,12,PSEUDO),
+ /* DWARF ABI defines RA_AUTH_CODE to 143. */
+ REGDEF(ra_auth_code,143,PSEUDO),
};
#undef REGDEF
#undef REGNUM
@@ -27905,7 +27932,6 @@ create_unwind_entry (int have_data)
return 0;
}
-
/* Initialize the DWARF-2 unwind information for this procedure. */
void
diff --git a/gas/testsuite/gas/arm/unwind-pacbti-m-readelf.d b/gas/testsuite/gas/arm/unwind-pacbti-m-readelf.d
index d8d647bb7f0..c40544a5a94 100644
--- a/gas/testsuite/gas/arm/unwind-pacbti-m-readelf.d
+++ b/gas/testsuite/gas/arm/unwind-pacbti-m-readelf.d
@@ -10,11 +10,11 @@ Unwind section '.ARM.exidx' at offset 0x60 contains 1 entry:
0x0 <foo>: @0x0
Compact model index: 1
- 0x84 0x00 pop {r14}
0xb4 pop {ra_auth_code}
0x84 0x00 pop {r14}
- 0xb4 pop {ra_auth_code}
0xa3 pop {r4, r5, r6, r7}
0xb4 pop {ra_auth_code}
+ 0x84 0x00 pop {r14}
+ 0xb4 pop {ra_auth_code}
0xa8 pop {r4, r14}
0xb0 finish
diff --git a/gas/testsuite/gas/arm/unwind-pacbti-m.d b/gas/testsuite/gas/arm/unwind-pacbti-m.d
index d178e4c0a44..b021c007b33 100644
--- a/gas/testsuite/gas/arm/unwind-pacbti-m.d
+++ b/gas/testsuite/gas/arm/unwind-pacbti-m.d
@@ -8,4 +8,4 @@
.*: file format.*
Contents of section .ARM.extab:
- 0000 (00840281 b40084b4 b0a8b4a3|81028400 b48400b4 a3b4a8b0) 00000000 .*
+ 0000 (84b40281 84b4a300 b0a8b400|8102b484 00a3b484 00b4a8b0) 00000000 .*
--
2.36.1
More information about the Binutils
mailing list