Re: [PATCH][gdb/testsuite] Fix gdb.dwarf2/dw2-dir-file-name.exp

[will schmidt <will_schmidt@vnet.ibm.com>]

On Tue, 2022-08-16 at 08:43 +0100, Luis Machado wrote:
> On 8/15/22 20:12, will schmidt wrote:
> > On Mon, 2022-08-15 at 09:54 -0700, Carl Love wrote:
> > > Tom:
> > > 
> > > OK, I took a look at how the test used to work and how it is now
> > > working and I see what the issue is.
> > > 
> > > PowerPC has two entry points, local and global.  The test used to set
> > > the breakpoint for the function at the local entry point.  With your
> > > changes, the breakpoint is now being set at the global breakpoint
> > > which
> > > is before the local breakpoint.  The function is actually entered at
> > > the local breakpoint thus gdb never "sees" the breakpoint that was
> > > set.
> > > Specfically, here is the objdump for the test:
> > > 
> > > 00000000100006e0 <compdir_missing__ldir_missing__file_basename>:
> > >      100006e0:   02 10 40
> > > 3c     lis     r2,4098                      <- Global entry point
> > >      100006e4:   00 7f 42 38     addi    r2,r2,32512
> > >      100006e8:   f8 ff e1 fb     std     r31,-8(r1)
> > >      100006ec:   d1 ff 21 f8     stdu    r1,-48(r1)
> > >      100006f0:   78 0b 3f 7c     mr      r31,r1
> > >      100006f4:   00 00 00
> > > 60     nop                                  <- Local entry point
> > >      100006f8:   28 81 22 39     addi    r9,r2,-32472
> > >      100006fc:   00 00 29 81     lwz     r9,0(r9)
> > >      10000700:   01 00 49 39     addi    r10,r9,1
> > >      10000704:   00 00 00 60     nop
> > >      10000708:   28 81 22 39     addi    r9,r2,-32472
> > >      1000070c:   00 00 49 91     stw     r10,0(r9)
> > >      10000710:   30 00 3f 38     addi    r1,r31,48
> > >      10000714:   f8 ff e1 eb     ld      r31,-8(r1)
> > >      10000718:   20 00 80 4e     blr
> > > 
> > > When I look at the output before the patch, we see:
> > > 
> > >     Breakpoint 2, 0x00000000100006f4 in
> > > compdir_missing__ldir_missing__file_basename () at tmp-dw2-dir-file-
> > > name.c:999
> > > 
> > >     (gdb) PASS: gdb.dwarf2/dw2-dir-file-name.exp:
> > > compdir_missing__ldir_missing__file_basename: continue to breakpoint:
> > > compdir_missing__ldir_missing__file_basename
> > >     set filename-display absolute
> > > 
> > > 
> > > Note the breakpoint 2 address is 0x00000000100006f4 which is on the
> > > NOP.  Instructions at addresses 0x100006e0 to 100006f0 are part of
> > > the
> > > code when the function is called via the global entry point.  So
> > > previously, the breakpoint was set at local entry point.
> > > 
> > > With the patch, we now see:
> > > 
> > >     Breakpoint 2 at 0x100006e0: file tmp-dw2-dir-file-name.c, line
> > > 999.
> > >     (gdb) continue
> > > 
> > >     Continuing.
> > >     [Inferior 1 (process 2520351) exited normally]
> > >     (gdb) FAIL: gdb.dwarf2/dw2-dir-file-name.exp:
> > > compdir_missing__ldir_missing__file_basename: continue to breakpoint:
> > > compdir_missing__ldir_missing__file_basename (the program exited)
> > > 
> > > Now we note that the breakpoint 2 is set at 0x100006e0 which is the
> > > global entry point.
> > > 
> > > It looks to me that we need to make sure we set the breakpoint at the
> > > local address.
> > > 
> > > Off hand, I am not sure how to get your changes to "proc
> > > gdb_continue_to_breakpoint" to select the local entry point not the
> > > global entry point.  Perhaps Ulrich has some ideas???
> > 
> >  From a glance that the patch that updated dw2-dir-file-name.exp;
> > ( commit cd919f5533cc8aa495acd75a6f059e5fcf2e6af9 )
> > the change there was effectively
> > 
> > -       gdb_breakpoint $func
> > +       gdb_breakpoint *$func
> > 
> > with assorted regexp changes to match.
> > 
> > The patch description goes into detail, but I interpret the gist of it
> > as avoiding the aarch64 architecture prologue skipper, since that
> > prologue skipper does something wrong, with entanglements in the line
> > table info.
> 
> Though the aarch64 prologue skipper is indeed mistaken here, Tom's patch only
> makes the test less reliant on whatever prologue skippers do and instead just
> got for a breakpoint straight at the entry point.

I don't have the code up in front of me, I'll punt to Carl to point out
where things are, if necessary.. :-) 

For PowerPC, as described in the
ELFv2 ABI, that entry point is the global entry point (GEP).  We also
have (and use as much as possible) a local entry point (LEP).  Code to
update the TOC pointer (R2) exists between the two entry points, so
when a local function calls this function, the TOC set-up is skipped. 
This was a significant part of the new ABI.

And though I was hung up on
the GEP/LEP gunk, I recognize the prologue skipping code also skips therest of the, um, prologue. 

It is perfectly fine to set a breakpoint between the two entry points,
or anywhere within the prologue, we just can't expect it to hit
anything between the entry points unless we are called via the global
entry point.

So for instance ... 

Dump of assembler code for function parse_size:
   0x000000000000091c <+0>:	addis   r2,r12,2   << GEP,*parse_size
   0x0000000000000920 <+4>:	addi    r2,r2,30180
   0x0000000000000924 <+8>:	mflr    r0         << LEP
   0x0000000000000928 <+12>:	std     r0,16(r1)
   0x000000000000092c <+16>:	std     r31,-8(r1)
   0x0000000000000930 <+20>:	stdu    r1,-144(r1)
   0x0000000000000934 <+24>:	mr      r31,r1
   0x0000000000000938 <+28>:	std     r3,104(r31) << End of Prologue.
   0x000000000000093c <+32>:	li      r9,1        << start

(gdb) break parse_size
Breakpoint 1 at 0x93c: file get_page_size.c, line
11.
(gdb) break *parse_size
Breakpoint 2 at 0x91c: file get_page_size.c,
line 9.
(gdb) break * 0x000000000000091c
Note: breakpoint 2 also set at
pc 0x91c.
Breakpoint 3 at 0x91c: file get_page_size.c, line 9.

Thanks,
-Will

> 
> It is a void function with void return type, so no much going on. Maybe it needs
> to be adapted somewhat to the PowerPC case?
> 
> 
> > The powerpc prologue skipper (wherever it is) was presumably handling
> > the local/global entry points properly.  Since the test now species a
> > specific address (*$func), the prologue skipper is no longer involved.
> 
> How does powerpc handle a breakpoint at a particular address?
> 
> > The patch should probably be reverted, but I defer to others if I've
> > misunderstood part of this issue..
> > 
> > Thanks
> > -Will
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > >                       Carl Love
> > > 
> > > 
> > > On Mon, 2022-08-15 at 09:01 -0700, Carl Love wrote:
> > > 
> > > > Looks like the patch was applied last Friday.  We are now seeing
> > > > 129
> > > > test failures related to this commit on PowerPC.  The failures are
> > > > seen
> > > > on Power 8, 9 and 10.
> > > > 
> > > > Here is an initial bit of the failures:
> > > > 
> > > > ...
> > > > Breakpoint 2 at 0x100006e0: file tmp-dw2-dir-file-name.c, line 999.
> > > > (gdb) continue
> > > > Continuing.
> > > > [Inferior 1 (process 2520351) exited normally]
> > > > (gdb) FAIL: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: continue to
> > > > breakpoint:
> > > > compdir_missing__ldir_missing__file_basename (the program exited)
> > > > set filename-display absolute
> > > > (gdb) PASS: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: set filename-display
> > > > absolute
> > > > expect: /home/carll/GDB/build-
> > > > current/gdb/testsuite/outputs/gdb.dwarf2/dw2-dir-file-name/dw2-dir-
> > > > file-name.d/rdir/tmp-dw2-dir-file-name.c
> > > > frame
> > > > No stack.
> > > > (gdb) FAIL: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: absolute
> > > > set filename-display basename
> > > > (gdb) PASS: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: set filename-display
> > > > basename
> > > > expect: tmp-dw2-dir-file-name.c
> > > > frame
> > > > No stack.
> > > > (gdb) FAIL: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: basename
> > > > set filename-display relative
> > > > (gdb) PASS: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: set filename-display
> > > > relative
> > > > expect: tmp-dw2-dir-file-name.c
> > > > frame
> > > > No stack.
> > > > (gdb) FAIL: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_basename: relative
> > > > set directories
> > > > (gdb) PASS: gdb.dwarf2/dw2-dir-file-name.exp:
> > > > compdir_missing__ldir_missing__file_relative: set directories
> > > > break *compdir_missing__ldir_missing__file_relative
> > > > Breakpoint 3 at 0x10000728: file fdir/tmp-dw2-dir-file-name.c, line
> > > > 999.
> > > > (gdb) continue
> > > > The program is not being run.
> > > > 
> > > > etc.
> > > > 
> > > > 		=== gdb Summary ===
> > > > 
> > > > # of expected passes		129
> > > > # of unexpected failures	128
> > > > 
> > > > I have not had time yet to try and dig into the failures to figure
> > > > out
> > > > the cause.  I will take a look at the failures to see what is going
> > > > on.
> > > > 
> > > > Anyway, just wanted to let you know what I am seeing on PowerPC.
> > > > 
> > > >                                  Carl
> > > > 
> > > > On Fri, 2022-08-12 at 10:33 +0100, Luis Machado via Gdb-patches
> > > > wrote:
> > > > > On 8/11/22 12:58, Tom de Vries wrote:
> > > > > > Hi,
> > > > > > 
> > > > > > When running test-case gdb.dwarf2/dw2-dir-file-name.exp on
> > > > > > x86_64-
> > > > > > linux, we
> > > > > > have:
> > > > > > ...
> > > > > > (gdb) break compdir_missing__ldir_missing__file_basename^M
> > > > > > Breakpoint 2 at 0x4004c4: file tmp-dw2-dir-file-name.c, line
> > > > > > 999.^M
> > > > > > (gdb) continue^M
> > > > > > Continuing.^M
> > > > > > ^M
> > > > > > Breakpoint 2, 0x00000000004004c4 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
> > > > > > ...
> > > > > > 
> > > > > > When trying to set a breakpoint on
> > > > > > compdir_missing__ldir_missing__file_basename, the architecture-
> > > > > > specific
> > > > > > prologue skipper starts at 0x4004c0 and skips past two insns,
> > > > > > to
> > > > > > 0x4004c4:
> > > > > > ...
> > > > > > 00000000004004c0
> > > > > > <compdir_missing__ldir_missing__file_basename>:
> > > > > >     4004c0: 55                      push   %rbp
> > > > > >     4004c1: 48 89 e5                mov    %rsp,%rbp
> > > > > >     4004c4: 8b 05 72 1b 20
> > > > > > 00       mov    0x201b72(%rip),%eax        # 60203c <v>
> > > > > >     4004ca: 83 c0 01                add    $0x1,%eax
> > > > > >     4004cd: 89 05 69 1b 20
> > > > > > 00       mov    %eax,0x201b69(%rip)        # 60203c <v>
> > > > > >     4004d3: 90                      nop
> > > > > >     4004d4: 5d                      pop    %rbp
> > > > > >     4004d5: c3                      ret
> > > > > > ...
> > > > > > 
> > > > > > And because the line table info is rudamentary:
> > > > > > ...
> > > > > > CU: tmp-dw2-dir-file-name.c:
> > > > > > File name                    Line number    Starting
> > > > > > address    View    Stmt
> > > > > > tmp-dw2-dir-file-
> > > > > > name.c              999            0x4004c0               x
> > > > > > tmp-dw2-dir-file-
> > > > > > name.c             1000            0x4004d6               x
> > > > > > tmp-dw2-dir-file-name.c                -            0x4004d6
> > > > > > ...
> > > > > > the address does not fall at an actual line, so the breakpoint
> > > > > > is
> > > > > > shown with
> > > > > > address, both when setting it and hitting it.
> > > > > > 
> > > > > > when running the test-case with aarch64-linux, we have
> > > > > > similarly:
> > > > > > ...
> > > > > > (gdb) break compdir_missing__ldir_missing__file_basename^M
> > > > > > Breakpoint 2 at 0x400618: file tmp-dw2-dir-file-name.c, line
> > > > > > 999.^M
> > > > > > ...
> > > > > > due to the architecture-specific prologue skipper starting at
> > > > > > 0x400610 and
> > > > > > skipping past two insns, to 0x400618:
> > > > > > ...
> > > > > > 0000000000400610
> > > > > > <compdir_missing__ldir_missing__file_basename>:
> > > > > >     400610:       90000100        adrp    x0, 420000 <
> > > > > > __libc_start_main@GLIBC_2.17>
> > > > > >     400614:       9100b000        add     x0, x0, #0x2c
> > > > > >     400618:       b9400000        ldr     w0, [x0]
> > > > > >     40061c:       11000401        add     w1, w0, #0x1
> > > > > >     400620:       90000100        adrp    x0, 420000 <
> > > > > > __libc_start_main@GLIBC_2.17>
> > > > > >     400624:       9100b000        add     x0, x0, #0x2c
> > > > > >     400628:       b9000001        str     w1, [x0]
> > > > > >     40062c:       d503201f        nop
> > > > > >     400630:       d65f03c0        ret
> > > > > > ...
> > > > > > 
> > > > > > But interestingly, the aarch64 architecture-specific prologue
> > > > > > skipper is
> > > > > > wrong.  There is no prologue, and the breakpoint should be set
> > > > > > at
> > > > > > 0x400610.
> > > > > > 
> > > > > > By using "break *compdir_missing__ldir_missing__file_basename"
> > > > > > we can get the breakpoint set at 0x400610:
> > > > > > ...
> > > > > > (gdb) break *compdir_missing__ldir_missing__file_basename^M
> > > > > > Breakpoint 2 at 0x400610: file tmp-dw2-dir-file-name.c, line
> > > > > > 999.^M
> > > > > > ...
> > > > > > and make the test-case independent of prologue analysis.
> > > > > > 
> > > > > > This requires us to update the expected patterns.
> > > > > > 
> > > > > > The fix ensures that once the aarch64 architecture-specific
> > > > > > prologue skipper
> > > > > > will be fixed, this test-case won't start failing.
> > > > > > 
> > > > > > Tested on x86_64-linux.
> > > > > > 
> > > > > > Any comments?
> > > > > > 
> > > > > > Thanks,
> > > > > > - Tom
> > > > > > 
> > > > > > [gdb/testsuite] Fix gdb.dwarf2/dw2-dir-file-name.exp
> > > > > > 
> > > > > > ---
> > > > > >    gdb/testsuite/gdb.dwarf2/dw2-dir-file-name.exp | 8 ++++----
> > > > > >    gdb/testsuite/lib/gdb.exp                      | 7 ++++++-
> > > > > >    2 files changed, 10 insertions(+), 5 deletions(-)
> > > > > > 
> > > > > > diff --git a/gdb/testsuite/gdb.dwarf2/dw2-dir-file-name.exp
> > > > > > b/gdb/testsuite/gdb.dwarf2/dw2-dir-file-name.exp
> > > > > > index 4d3f767f597..4c4c1ff07af 100644
> > > > > > --- a/gdb/testsuite/gdb.dwarf2/dw2-dir-file-name.exp
> > > > > > +++ b/gdb/testsuite/gdb.dwarf2/dw2-dir-file-name.exp
> > > > > > @@ -396,20 +396,20 @@ proc test { func compdir filename } {
> > > > > >    	    error "not absolute"
> > > > > >    	}
> > > > > >    
> > > > > > -	gdb_breakpoint $func
> > > > > > +	gdb_breakpoint *$func
> > > > > >    	gdb_continue_to_breakpoint $func "$func \\(\\) at .*"
> > > > > >    
> > > > > >    	gdb_test_no_output "set filename-display absolute"
> > > > > >    	verbose -log "expect: ${absolute}"
> > > > > > -	gdb_test "frame" " in $func \\(\\) at [string_to_regexp
> > > > > > ${absolute}]:999" "absolute"
> > > > > > +	gdb_test "frame" "#0  $func \\(\\) at [string_to_regexp
> > > > > > ${absolute}]:999" "absolute"
> > > > > >    
> > > > > >    	gdb_test_no_output "set filename-display basename"
> > > > > >    	verbose -log "expect: [file tail $filename]"
> > > > > > -	gdb_test "frame" " in $func \\(\\) at [string_to_regexp
> > > > > > [file
> > > > > > tail $filename]]:999" "basename"
> > > > > > +	gdb_test "frame" "#0  $func \\(\\) at [string_to_regexp
> > > > > > [file
> > > > > > tail $filename]]:999" "basename"
> > > > > >    
> > > > > >    	gdb_test_no_output "set filename-display relative"
> > > > > >    	verbose -log "expect: $filename"
> > > > > > -	gdb_test "frame" " in $func \\(\\) at [string_to_regexp
> > > > > > $filename]:999" "relative"
> > > > > > +	gdb_test "frame" "#0  $func \\(\\) at [string_to_regexp
> > > > > > $filename]:999" "relative"
> > > > > >        }
> > > > > >    }
> > > > > >    
> > > > > > diff --git a/gdb/testsuite/lib/gdb.exp
> > > > > > b/gdb/testsuite/lib/gdb.exp
> > > > > > index a8f25b5f0dd..70fc019eeb9 100644
> > > > > > --- a/gdb/testsuite/lib/gdb.exp
> > > > > > +++ b/gdb/testsuite/lib/gdb.exp
> > > > > > @@ -787,9 +787,14 @@ proc gdb_continue_to_breakpoint {name
> > > > > > {location_pattern .*}} {
> > > > > >        global gdb_prompt
> > > > > >        set full_name "continue to breakpoint: $name"
> > > > > >    
> > > > > > +    set re_at_in " (at|in) "                          <-NEED
> > > > > > TO FIX TO ALWAYS GIVE local entry point for POWERPC
> > > > > > ??
> > > > > >       
> > > > > > +    if { [regexp $re_at_in $location_pattern] } {
> > > > > > +	set re_at_in " "
> > > > > > +    }
> > > > > > +
> > > > > >        set kfail_pattern "Process record does not support
> > > > > > instruction 0xfae64 at.*"
> > > > > >        gdb_test_multiple "continue" $full_name {
> > > > > > -	-re "(?:Breakpoint|Temporary breakpoint) .* (at|in)
> > > > > > $location_pattern\r\n$gdb_prompt $" {
> > > > > > +	-re "(?:Breakpoint|Temporary breakpoint)
> > > > > > .*$re_at_in$location_pattern\r\n$gdb_prompt $" {
> > > > > >    	    pass $full_name
> > > > > >    	}
> > > > > >    	-re "\[\r\n\]*(?:$kfail_pattern)\[\r\n\]+$gdb_prompt $"
> > > > > > {