[2/2] Improve arm_skip_prologue by using arm_analyze_prologue
Commit Message
Hi,
I see many fails in dw2-dir-file-name.exp on arm target when test
case is compiled with -marm, however, these fails are disappeared when
test case is compiled with -mthumb.
The difference of pass and fail shown below is that "0x000085d4 in" isn't
printed out, but test case expects to see it.
-Breakpoint 2, compdir_missing__ldir_missing__file_basename () at tmp-dw2-dir-file-name.c:999^M
-(gdb) FAIL: gdb.dwarf2/dw2-dir-file-name.exp: compdir_missing__ldir_missing__file_basename: continue to breakpoint: compdir_missing__ldir_missing__file_basename
+Breakpoint 2, 0x000085d4 in compdir_missing__ldir_missing__file_basename () at tmp-dw2-dir-file-name.c:999^M
+(gdb) PASS: gdb.dwarf2/dw2-dir-file-name.exp: compdir_missing__ldir_missing__file_basename: continue to breakpoint: compdir_missing__ldir_missing__file_basename
This difference is caused by setting breakpoint at the first instruction
in the function (actually, the first instruction in prologue, at [1]),
so that frame_show_address returns false, and print_frame doesn't print the
address.
0x00008620 <+0>: push {r11} ; (str r11, [sp, #-4]!) <--[1]
0x00008624 <+4>: add r11, sp, #0
0x00008628 <+8>: ldr r3, [pc, #24] ; 0x8648 <compdir_missing__ldir_missing__file_basename+40>
0x0000862c <+12>: ldr r3, [r3]
0x00008630 <+16>: add r3, r3, #1
0x00008634 <+20>: ldr r2, [pc, #12] ; 0x8648 <compdir_missing__ldir_missing__file_basename+40>
Then, it must be the arm_skip_prologue's fault that unable to skip
instructions in prologue. At the end of arm_skip_prologue, it matches
several instructions, such as "str r(0123),[r11,#-nn]" and
"str r(0123),[sp,#nn]", but "push {r11}" isn't handled.
These instruction matching code in arm_skip_prologue, which can be regarded
as leftover of development for many years, should be merged to
arm_analyze_prologue and use arm_analyze_prologue in arm_skip_prologue.
Here is the something like the history of arm_{skip,scan,analyze}_prologue.
Around 2002, there are arm_skip_prologue and arm_scan_prologue, but code are
duplicated to some extent. When match an instruction, both functions should
be modified, for example in Michael Snyder's patch
https://sourceware.org/ml/gdb-patches/2002-05/msg00205.html and Michael
expressed the willingness to merge both into one. Daniel added code call
thumb_analyze_prologue in arm_skip_prologue in 2006, but didn't handle its
counterpart arm_analyze_prologue, which is added in 2010
<https://sourceware.org/ml/gdb-patches/2010-03/msg00820.html>
however, the instructions matching at the bottom of arm_skip_prologue wasn't
cleaned up. This patch is to merge them into arm_analyze_prologue.
Note 1: I recall some one opened a PR for these fails, but I can't find
it in bugzilla.
Note 2: This patch should also fix PR 14261, but I don't have a CLANG to
test it.
gdb:
2014-11-30 Yao Qi <yao@codesourcery.com>
* arm-tdep.c (arm_skip_prologue): Remove unused local variable
'skip_pc'. Remove code skipping prologue instructions, use
arm_analyze_prologue instead.
(arm_analyze_prologue): Stop the scanning for unrecognized
instruction when skipping prologue.
---
gdb/arm-tdep.c | 75 ++++++++++------------------------------------------------
1 file changed, 12 insertions(+), 63 deletions(-)
@@ -1388,7 +1388,6 @@ arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
unsigned long inst;
- CORE_ADDR skip_pc;
CORE_ADDR func_addr, limit_pc;
/* See if we can determine the end of the prologue via the symbol table.
@@ -1462,65 +1461,8 @@ arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
/* Check if this is Thumb code. */
if (arm_pc_is_thumb (gdbarch, pc))
return thumb_analyze_prologue (gdbarch, pc, limit_pc, NULL);
-
- for (skip_pc = pc; skip_pc < limit_pc; skip_pc += 4)
- {
- inst = read_memory_unsigned_integer (skip_pc, 4, byte_order_for_code);
-
- /* "mov ip, sp" is no longer a required part of the prologue. */
- if (inst == 0xe1a0c00d) /* mov ip, sp */
- continue;
-
- if ((inst & 0xfffff000) == 0xe28dc000) /* add ip, sp #n */
- continue;
-
- if ((inst & 0xfffff000) == 0xe24dc000) /* sub ip, sp #n */
- continue;
-
- /* Some prologues begin with "str lr, [sp, #-4]!". */
- if (inst == 0xe52de004) /* str lr, [sp, #-4]! */
- continue;
-
- if ((inst & 0xfffffff0) == 0xe92d0000) /* stmfd sp!,{a1,a2,a3,a4} */
- continue;
-
- if ((inst & 0xfffff800) == 0xe92dd800) /* stmfd sp!,{fp,ip,lr,pc} */
- continue;
-
- /* Any insns after this point may float into the code, if it makes
- for better instruction scheduling, so we skip them only if we
- find them, but still consider the function to be frame-ful. */
-
- /* We may have either one sfmfd instruction here, or several stfe
- insns, depending on the version of floating point code we
- support. */
- if ((inst & 0xffbf0fff) == 0xec2d0200) /* sfmfd fn, <cnt>, [sp]! */
- continue;
-
- if ((inst & 0xffff8fff) == 0xed6d0103) /* stfe fn, [sp, #-12]! */
- continue;
-
- if ((inst & 0xfffff000) == 0xe24cb000) /* sub fp, ip, #nn */
- continue;
-
- if ((inst & 0xfffff000) == 0xe24dd000) /* sub sp, sp, #nn */
- continue;
-
- if ((inst & 0xffffc000) == 0xe54b0000 /* strb r(0123),[r11,#-nn] */
- || (inst & 0xffffc0f0) == 0xe14b00b0 /* strh r(0123),[r11,#-nn] */
- || (inst & 0xffffc000) == 0xe50b0000) /* str r(0123),[r11,#-nn] */
- continue;
-
- if ((inst & 0xffffc000) == 0xe5cd0000 /* strb r(0123),[sp,#nn] */
- || (inst & 0xffffc0f0) == 0xe1cd00b0 /* strh r(0123),[sp,#nn] */
- || (inst & 0xffffc000) == 0xe58d0000) /* str r(0123),[sp,#nn] */
- continue;
-
- /* Un-recognized instruction; stop scanning. */
- break;
- }
-
- return skip_pc; /* End of prologue. */
+ else
+ return arm_analyze_prologue (gdbarch, pc, limit_pc, NULL);
}
/* *INDENT-OFF* */
@@ -1905,10 +1847,17 @@ arm_analyze_prologue (struct gdbarch *gdbarch,
continue;
else
{
- /* The optimizer might shove anything into the prologue,
- so we just skip what we don't recognize. */
+ /* The optimizer might shove anything into the prologue, if
+ we build up cache (cache != NULL) from scanning prologue,
+ we just skip what we don't recognize and scan further to
+ make cache as complete as possible. However, if we skip
+ prologue, we'll stop immediately on unrecognized
+ instruction. */
unrecognized_pc = current_pc;
- continue;
+ if (cache != NULL)
+ continue;
+ else
+ break;
}
}