Patchwork AArch64: Allow additional sizes in prologue

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Submitter Alan Hayward
Date Aug. 5, 2019, 12:41 p.m.
Message ID <20190805124152.26127-1-alan.hayward@arm.com>
Download mbox | patch
Permalink /patch/33964/
State New
Headers show

Comments

Alan Hayward - Aug. 5, 2019, 12:41 p.m.
When saving registers to the stack at the start of a function, not all state
needs to be saved. For example, only the first 64bits of float registers need
saving.  However, a program may choose to store extra state if it wishes,
there is nothing preventing it doing so.

The aarch64_analyze_prologue will error if it detects extra state being
stored.  Relex this restriction.

Tested via aarch64-prologue test.

gdb/ChangeLog:

2019-08-05  Alan Hayward  <alan.hayward@arm.com>

	* aarch64-tdep.c (aarch64_analyze_prologue): Allow any valid
	register sizes.

gdb/testsuite/ChangeLog:

2019-08-05  Alan Hayward  <alan.hayward@arm.com>

	* gdb.arch/aarch64-prologue.c: New test.
	* gdb.arch/aarch64-prologue.exp: New file.
---
 gdb/aarch64-tdep.c                          | 28 ++-----
 gdb/testsuite/gdb.arch/aarch64-prologue.c   | 83 +++++++++++++++++++++
 gdb/testsuite/gdb.arch/aarch64-prologue.exp | 36 +++++++++
 3 files changed, 127 insertions(+), 20 deletions(-)
 create mode 100644 gdb/testsuite/gdb.arch/aarch64-prologue.c
 create mode 100644 gdb/testsuite/gdb.arch/aarch64-prologue.exp
Tom Tromey - Aug. 5, 2019, 5:43 p.m.
>>>>> "Alan" == Alan Hayward <Alan.Hayward@arm.com> writes:

Alan> When saving registers to the stack at the start of a function, not all state
Alan> needs to be saved. For example, only the first 64bits of float registers need
Alan> saving.  However, a program may choose to store extra state if it wishes,
Alan> there is nothing preventing it doing so.

Alan> The aarch64_analyze_prologue will error if it detects extra state being
Alan> stored.  Relex this restriction.

I don't know anything about AArch64, so I can't really comment on the
content of the patch, but I did happen to see a nit:

Alan>  	  stack.store (pv_add_constant (regs[rn],
Alan>  					inst.operands[1].addr.offset.imm),
Alan> -		       is64 ? 8 : 4, regs[rt]);
Alan> +					size, regs[rt]);

...this addition looked mis-indented to me.

Tom
Alan Hayward - Aug. 6, 2019, 8:58 a.m.
> On 5 Aug 2019, at 18:43, Tom Tromey <tom@tromey.com> wrote:
> 
>>>>>> "Alan" == Alan Hayward <Alan.Hayward@arm.com> writes:
> 
> Alan> When saving registers to the stack at the start of a function, not all state
> Alan> needs to be saved. For example, only the first 64bits of float registers need
> Alan> saving.  However, a program may choose to store extra state if it wishes,
> Alan> there is nothing preventing it doing so.
> 
> Alan> The aarch64_analyze_prologue will error if it detects extra state being
> Alan> stored.  Relex this restriction.
> 
> I don't know anything about AArch64, so I can't really comment on the
> content of the patch, but I did happen to see a nit:
> 
> Alan>  	  stack.store (pv_add_constant (regs[rn],
> Alan>  					inst.operands[1].addr.offset.imm),
> Alan> -		       is64 ? 8 : 4, regs[rt]);
> Alan> +					size, regs[rt]);
> 
> ...this addition looked mis-indented to me.

Thanks.
I probably missed that because the correct formatting looks horrible:

	  stack.store (pv_add_constant (regs[rn],
					inst.operands[1].addr.offset.imm),
		       size, regs[rt]);

Instead, I can update it to the following

	  stack.store (
	    pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm),
	    size, regs[rt]);


> 
> Tom
Richard Earnshaw (lists) - Aug. 6, 2019, 9:56 a.m.
On 06/08/2019 09:58, Alan Hayward wrote:
> 
> 
>> On 5 Aug 2019, at 18:43, Tom Tromey <tom@tromey.com> wrote:
>>
>>>>>>> "Alan" == Alan Hayward <Alan.Hayward@arm.com> writes:
>>
>> Alan> When saving registers to the stack at the start of a function, not all state
>> Alan> needs to be saved. For example, only the first 64bits of float registers need
>> Alan> saving.  However, a program may choose to store extra state if it wishes,
>> Alan> there is nothing preventing it doing so.
>>
>> Alan> The aarch64_analyze_prologue will error if it detects extra state being
>> Alan> stored.  Relex this restriction.
>>
>> I don't know anything about AArch64, so I can't really comment on the
>> content of the patch, but I did happen to see a nit:
>>
>> Alan>  	  stack.store (pv_add_constant (regs[rn],
>> Alan>  					inst.operands[1].addr.offset.imm),
>> Alan> -		       is64 ? 8 : 4, regs[rt]);
>> Alan> +					size, regs[rt]);
>>
>> ...this addition looked mis-indented to me.
> 
> Thanks.
> I probably missed that because the correct formatting looks horrible:
> 
> 	  stack.store (pv_add_constant (regs[rn],
> 					inst.operands[1].addr.offset.imm),
> 		       size, regs[rt]);
> 
> Instead, I can update it to the following
> 
> 	  stack.store (
> 	    pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm),
> 	    size, regs[rt]);
> 

I think the coding convention in that case is to write:


	  stack.store
             (pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm),
	     size, regs[rt]);

R.

>>
>> Tom
>
Alan Hayward - Aug. 6, 2019, 12:18 p.m.
> On 6 Aug 2019, at 10:56, Richard Earnshaw (lists) <Richard.Earnshaw@arm.com> wrote:
> 
> On 06/08/2019 09:58, Alan Hayward wrote:
>>> On 5 Aug 2019, at 18:43, Tom Tromey <tom@tromey.com> wrote:
>>> 
>>>>>>>> "Alan" == Alan Hayward <Alan.Hayward@arm.com> writes:
>>> 
>>> Alan> When saving registers to the stack at the start of a function, not all state
>>> Alan> needs to be saved. For example, only the first 64bits of float registers need
>>> Alan> saving.  However, a program may choose to store extra state if it wishes,
>>> Alan> there is nothing preventing it doing so.
>>> 
>>> Alan> The aarch64_analyze_prologue will error if it detects extra state being
>>> Alan> stored.  Relex this restriction.
>>> 
>>> I don't know anything about AArch64, so I can't really comment on the
>>> content of the patch, but I did happen to see a nit:
>>> 
>>> Alan>  	  stack.store (pv_add_constant (regs[rn],
>>> Alan>  					inst.operands[1].addr.offset.imm),
>>> Alan> -		       is64 ? 8 : 4, regs[rt]);
>>> Alan> +					size, regs[rt]);
>>> 
>>> ...this addition looked mis-indented to me.
>> Thanks.
>> I probably missed that because the correct formatting looks horrible:
>> 	  stack.store (pv_add_constant (regs[rn],
>> 					inst.operands[1].addr.offset.imm),
>> 		       size, regs[rt]);
>> Instead, I can update it to the following
>> 	  stack.store (
>> 	    pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm),
>> 	    size, regs[rt]);
> 
> I think the coding convention in that case is to write:
> 
> 
> 	  stack.store
>            (pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm),
> 	     size, regs[rt]);
> 
> R.

Ok, will use that way.

Alan.
Tom Tromey - Aug. 6, 2019, 1:52 p.m.
>>>>> "Alan" == Alan Hayward <Alan.Hayward@arm.com> writes:

Alan> I probably missed that because the correct formatting looks horrible:

Alan> 	  stack.store (pv_add_constant (regs[rn],
Alan> 					inst.operands[1].addr.offset.imm),
Alan> 		       size, regs[rt]);

This is a pretty normal style you'd see in gdb.

Alan> Instead, I can update it to the following

Alan> 	  stack.store (
Alan> 	    pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm),
Alan> 	    size, regs[rt]);

gdb doesn't normally use the trailing open paren style like that.

Tom

Patch

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index e23cc3f956..1926e54c3c 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -384,8 +384,7 @@  aarch64_analyze_prologue (struct gdbarch *gdbarch,
 	{
 	  unsigned rt = inst.operands[0].reg.regno;
 	  unsigned rn = inst.operands[1].addr.base_regno;
-	  int is64
-	    = (aarch64_get_qualifier_esize (inst.operands[0].qualifier) == 8);
+	  int size = aarch64_get_qualifier_esize (inst.operands[0].qualifier);
 
 	  gdb_assert (aarch64_num_of_operands (inst.opcode) == 2);
 	  gdb_assert (inst.operands[0].type == AARCH64_OPND_Rt);
@@ -394,7 +393,7 @@  aarch64_analyze_prologue (struct gdbarch *gdbarch,
 
 	  stack.store (pv_add_constant (regs[rn],
 					inst.operands[1].addr.offset.imm),
-		       is64 ? 8 : 4, regs[rt]);
+					size, regs[rt]);
 	}
       else if ((inst.opcode->iclass == ldstpair_off
 		|| (inst.opcode->iclass == ldstpair_indexed
@@ -406,6 +405,7 @@  aarch64_analyze_prologue (struct gdbarch *gdbarch,
 	  unsigned rt2;
 	  unsigned rn = inst.operands[2].addr.base_regno;
 	  int32_t imm = inst.operands[2].addr.offset.imm;
+	  int size = aarch64_get_qualifier_esize (inst.operands[0].qualifier);
 
 	  gdb_assert (inst.operands[0].type == AARCH64_OPND_Rt
 		      || inst.operands[0].type == AARCH64_OPND_Ft);
@@ -427,17 +427,12 @@  aarch64_analyze_prologue (struct gdbarch *gdbarch,
 	  rt2 = inst.operands[1].reg.regno;
 	  if (inst.operands[0].type == AARCH64_OPND_Ft)
 	    {
-	      /* Only bottom 64-bit of each V register (D register) need
-		 to be preserved.  */
-	      gdb_assert (inst.operands[0].qualifier == AARCH64_OPND_QLF_S_D);
 	      rt1 += AARCH64_X_REGISTER_COUNT;
 	      rt2 += AARCH64_X_REGISTER_COUNT;
 	    }
 
-	  stack.store (pv_add_constant (regs[rn], imm), 8,
-		       regs[rt1]);
-	  stack.store (pv_add_constant (regs[rn], imm + 8), 8,
-		       regs[rt2]);
+	  stack.store (pv_add_constant (regs[rn], imm), size, regs[rt1]);
+	  stack.store (pv_add_constant (regs[rn], imm + size), size, regs[rt2]);
 
 	  if (inst.operands[2].addr.writeback)
 	    regs[rn] = pv_add_constant (regs[rn], imm);
@@ -454,21 +449,14 @@  aarch64_analyze_prologue (struct gdbarch *gdbarch,
 	  unsigned int rt = inst.operands[0].reg.regno;
 	  int32_t imm = inst.operands[1].addr.offset.imm;
 	  unsigned int rn = inst.operands[1].addr.base_regno;
-	  bool is64
-	    = (aarch64_get_qualifier_esize (inst.operands[0].qualifier) == 8);
+	  int size = aarch64_get_qualifier_esize (inst.operands[0].qualifier);
 	  gdb_assert (inst.operands[0].type == AARCH64_OPND_Rt
 		      || inst.operands[0].type == AARCH64_OPND_Ft);
 
 	  if (inst.operands[0].type == AARCH64_OPND_Ft)
-	    {
-	      /* Only bottom 64-bit of each V register (D register) need
-		 to be preserved.  */
-	      gdb_assert (inst.operands[0].qualifier == AARCH64_OPND_QLF_S_D);
-	      rt += AARCH64_X_REGISTER_COUNT;
-	    }
+	    rt += AARCH64_X_REGISTER_COUNT;
 
-	  stack.store (pv_add_constant (regs[rn], imm),
-		       is64 ? 8 : 4, regs[rt]);
+	  stack.store (pv_add_constant (regs[rn], imm), size, regs[rt]);
 	  if (inst.operands[1].addr.writeback)
 	    regs[rn] = pv_add_constant (regs[rn], imm);
 	}
diff --git a/gdb/testsuite/gdb.arch/aarch64-prologue.c b/gdb/testsuite/gdb.arch/aarch64-prologue.c
new file mode 100644
index 0000000000..aa664f704f
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/aarch64-prologue.c
@@ -0,0 +1,83 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2019 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+
+extern void excessiveprologue ();
+
+void
+innerfunc ()
+{
+  printf ("inner\n");
+}
+
+/* excessiveprologue saves to the stack in multiple ways.  */
+
+asm ("\t.section .gnu.sgstubs,\"ax\",%progbits\n"
+     "\t.global excessiveprologue\n"
+     "\t.type excessiveprologue, %function\n"
+     "excessiveprologue:\n"
+     "\tstp	x29, x30, [sp, #-208]!\n"
+     "\tmov	x29, sp\n"
+     "\tstp	w0,w1,[sp,16]\n"
+     "\tstp	x2,x3,[sp,24]\n"
+     "\tstr	w4,[sp,40]\n"
+     "\tstr	x5,[sp,48]\n"
+     "\tstur	w6,[sp,52]\n"
+     "\tstur	x7,[sp,56]\n"
+     "\tstp	s0,s1,[sp,64]\n"
+     "\tstp	d2,d3,[sp,72]\n"
+     "\tstp	q4,q5,[sp,96]\n"
+     "\tstr	b6,[sp,128]\n"
+     "\tstr	h7,[sp,132]\n"
+     "\tstr	s8,[sp,136]\n"
+     "\tstr	d9,[sp,140]\n"
+     "\tstr	q10,[sp,148]\n"
+     "\tstur	b11,[sp,164]\n"
+     "\tstur	h12,[sp,160]\n"
+     "\tstur	s13,[sp,172]\n"
+     "\tstur	d14,[sp,176]\n"
+     "\tstur	q15,[sp,184]\n"
+     "\tbl innerfunc\n"
+     "\tldp	w0,w1,[sp,16]\n"
+     "\tldp	x2,x3,[sp,24]\n"
+     "\tldr	w4,[sp,40]\n"
+     "\tldr	x5,[sp,48]\n"
+     "\tldur	w6,[sp,52]\n"
+     "\tldur	x7,[sp,56]\n"
+     "\tldp	s0,s1,[sp,64]\n"
+     "\tldp	d2,d3,[sp,72]\n"
+     "\tldp	q4,q5,[sp,96]\n"
+     "\tldr	b6,[sp,128]\n"
+     "\tldr	h7,[sp,132]\n"
+     "\tldr	s8,[sp,136]\n"
+     "\tldr	d9,[sp,140]\n"
+     "\tldr	q10,[sp,148]\n"
+     "\tldur	b11,[sp,164]\n"
+     "\tldur	h12,[sp,160]\n"
+     "\tldur	s13,[sp,172]\n"
+     "\tldur	d14,[sp,176]\n"
+     "\tldur	q15,[sp,184]\n"
+     "\tldp	x29, x30, [sp], #208\n"
+     "ret\n");
+
+int
+main (void)
+{
+  excessiveprologue ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.arch/aarch64-prologue.exp b/gdb/testsuite/gdb.arch/aarch64-prologue.exp
new file mode 100644
index 0000000000..e31261ad25
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/aarch64-prologue.exp
@@ -0,0 +1,36 @@ 
+# Copyright 2019 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This file is part of the gdb testsuite.
+
+if {![is_aarch64_target]} {
+    verbose "Skipping ${gdb_test_file_name}."
+    return 1
+}
+
+standard_testfile
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile {nodebug}]} {
+    return -1
+}
+
+if ![runto_main] {
+   untested "could not run to main"
+   return -1
+}
+
+# Ensure gdb can break at excessiveprologue then continue.
+gdb_breakpoint "excessiveprologue"
+gdb_continue_to_breakpoint "excessiveprologue"
+gdb_continue_to_end "excessiveprologue" "continue" 1