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gdb: set current thread in sparc_{fetch,collect}_inferior_registers (PR gdb/27147)
PR 27147 shows that on sparc64, GDB is unable to properly unwind:
Expected result (from GDB 9.2):
#0 0x0000000000108de4 in puts ()
#1 0x0000000000100950 in hello () at gdb-test.c:4
#2 0x0000000000100968 in main () at gdb-test.c:8
Actual result (from GDB latest git):
#0 0x0000000000108de4 in puts ()
#1 0x0000000000100950 in hello () at gdb-test.c:4
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
The first failing commit is 5b6d1e4fa4 ("Multi-target support"). The cause
of the change in behavior is due to (thanks for Andrew Burgess for finding
this):
- inferior_ptid is no longer set on entry of target_ops::wait, whereas
it was set to something valid previously
- deep down in linux_nat_target::wait (see stack trace below), we fetch
the registers of the event thread
- on sparc64, fetching registers involves reading memory (in
sparc_supply_rwindow, see stack trace below)
- reading memory (target_ops::xfer_partial) relies on inferior_ptid
being set to the thread from which we want to read memory
This is where things go wrong:
#0 linux_nat_target::xfer_partial (this=0x10000fa2c40 <the_sparc64_linux_nat_target>, object=TARGET_OBJECT_MEMORY, annex=0x0, readbuf=0x7feffe3b000 "", writebuf=0x0, offset=8791798050744, len=8, xfered_len=0x7feffe3ae88) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:3697
#1 0x00000100007f5b10 in raw_memory_xfer_partial (ops=0x10000fa2c40 <the_sparc64_linux_nat_target>, readbuf=0x7feffe3b000 "", writebuf=0x0, memaddr=8791798050744, len=8, xfered_len=0x7feffe3ae88) at /home/simark/src/binutils-gdb/gdb/target.c:912
#2 0x00000100007f60e8 in memory_xfer_partial_1 (ops=0x10000fa2c40 <the_sparc64_linux_nat_target>, object=TARGET_OBJECT_MEMORY, readbuf=0x7feffe3b000 "", writebuf=0x0, memaddr=8791798050744, len=8, xfered_len=0x7feffe3ae88) at /home/simark/src/binutils-gdb/gdb/target.c:1043
#3 0x00000100007f61b4 in memory_xfer_partial (ops=0x10000fa2c40 <the_sparc64_linux_nat_target>, object=TARGET_OBJECT_MEMORY, readbuf=0x7feffe3b000 "", writebuf=0x0, memaddr=8791798050744, len=8, xfered_len=0x7feffe3ae88) at /home/simark/src/binutils-gdb/gdb/target.c:1072
#4 0x00000100007f6538 in target_xfer_partial (ops=0x10000fa2c40 <the_sparc64_linux_nat_target>, object=TARGET_OBJECT_MEMORY, annex=0x0, readbuf=0x7feffe3b000 "", writebuf=0x0, offset=8791798050744, len=8, xfered_len=0x7feffe3ae88) at /home/simark/src/binutils-gdb/gdb/target.c:1129
#5 0x00000100007f7094 in target_read_partial (ops=0x10000fa2c40 <the_sparc64_linux_nat_target>, object=TARGET_OBJECT_MEMORY, annex=0x0, buf=0x7feffe3b000 "", offset=8791798050744, len=8, xfered_len=0x7feffe3ae88) at /home/simark/src/binutils-gdb/gdb/target.c:1375
#6 0x00000100007f721c in target_read (ops=0x10000fa2c40 <the_sparc64_linux_nat_target>, object=TARGET_OBJECT_MEMORY, annex=0x0, buf=0x7feffe3b000 "", offset=8791798050744, len=8) at /home/simark/src/binutils-gdb/gdb/target.c:1415
#7 0x00000100007f69d4 in target_read_memory (memaddr=8791798050744, myaddr=0x7feffe3b000 "", len=8) at /home/simark/src/binutils-gdb/gdb/target.c:1218
#8 0x0000010000758520 in sparc_supply_rwindow (regcache=0x10000fea4f0, sp=8791798050736, regnum=-1) at /home/simark/src/binutils-gdb/gdb/sparc-tdep.c:1960
#9 0x000001000076208c in sparc64_supply_gregset (gregmap=0x10000be3190 <sparc64_linux_ptrace_gregmap>, regcache=0x10000fea4f0, regnum=-1, gregs=0x7feffe3b230) at /home/simark/src/binutils-gdb/gdb/sparc64-tdep.c:1974
#10 0x0000010000751b64 in sparc_fetch_inferior_registers (regcache=0x10000fea4f0, regnum=80) at /home/simark/src/binutils-gdb/gdb/sparc-nat.c:170
#11 0x0000010000759d68 in sparc64_linux_nat_target::fetch_registers (this=0x10000fa2c40 <the_sparc64_linux_nat_target>, regcache=0x10000fea4f0, regnum=80) at /home/simark/src/binutils-gdb/gdb/sparc64-linux-nat.c:38
#12 0x00000100008146ec in target_fetch_registers (regcache=0x10000fea4f0, regno=80) at /home/simark/src/binutils-gdb/gdb/target.c:3287
#13 0x00000100006a8c5c in regcache::raw_update (this=0x10000fea4f0, regnum=80) at /home/simark/src/binutils-gdb/gdb/regcache.c:584
#14 0x00000100006a8d94 in readable_regcache::raw_read (this=0x10000fea4f0, regnum=80, buf=0x7feffe3b7c0 "") at /home/simark/src/binutils-gdb/gdb/regcache.c:598
#15 0x00000100006a93b8 in readable_regcache::cooked_read (this=0x10000fea4f0, regnum=80, buf=0x7feffe3b7c0 "") at /home/simark/src/binutils-gdb/gdb/regcache.c:690
#16 0x00000100006b288c in readable_regcache::cooked_read<unsigned long, void> (this=0x10000fea4f0, regnum=80, val=0x7feffe3b948) at /home/simark/src/binutils-gdb/gdb/regcache.c:777
#17 0x00000100006a9b44 in regcache_cooked_read_unsigned (regcache=0x10000fea4f0, regnum=80, val=0x7feffe3b948) at /home/simark/src/binutils-gdb/gdb/regcache.c:791
#18 0x00000100006abf3c in regcache_read_pc (regcache=0x10000fea4f0) at /home/simark/src/binutils-gdb/gdb/regcache.c:1295
#19 0x0000010000507920 in save_stop_reason (lp=0x10000fc5b10) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:2612
#20 0x00000100005095a4 in linux_nat_filter_event (lwpid=520983, status=1407) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:3050
#21 0x0000010000509f9c in linux_nat_wait_1 (ptid=..., ourstatus=0x7feffe3c8f0, target_options=...) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:3194
#22 0x000001000050b1d0 in linux_nat_target::wait (this=0x10000fa2c40 <the_sparc64_linux_nat_target>, ptid=..., ourstatus=0x7feffe3c8f0, target_options=...) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:3432
#23 0x00000100007f8ac0 in target_wait (ptid=..., status=0x7feffe3c8f0, options=...) at /home/simark/src/binutils-gdb/gdb/target.c:2000
#24 0x00000100004ac17c in do_target_wait_1 (inf=0x1000116d280, ptid=..., status=0x7feffe3c8f0, options=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:3464
#25 0x00000100004ac3b8 in operator() (__closure=0x7feffe3c678, inf=0x1000116d280) at /home/simark/src/binutils-gdb/gdb/infrun.c:3527
#26 0x00000100004ac7cc in do_target_wait (wait_ptid=..., ecs=0x7feffe3c8c8, options=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:3540
#27 0x00000100004ad8c4 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:3880
#28 0x0000010000485568 in inferior_event_handler (event_type=INF_REG_EVENT) at /home/simark/src/binutils-gdb/gdb/inf-loop.c:42
#29 0x000001000050d394 in handle_target_event (error=0, client_data=0x0) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:4060
#30 0x0000010000ab5c8c in handle_file_event (file_ptr=0x10001207270, ready_mask=1) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:575
#31 0x0000010000ab6334 in gdb_wait_for_event (block=0) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:701
#32 0x0000010000ab487c in gdb_do_one_event () at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:212
#33 0x0000010000542668 in start_event_loop () at /home/simark/src/binutils-gdb/gdb/main.c:348
#34 0x000001000054287c in captured_command_loop () at /home/simark/src/binutils-gdb/gdb/main.c:408
#35 0x0000010000544e84 in captured_main (data=0x7feffe3d188) at /home/simark/src/binutils-gdb/gdb/main.c:1242
#36 0x0000010000544f2c in gdb_main (args=0x7feffe3d188) at /home/simark/src/binutils-gdb/gdb/main.c:1257
#37 0x00000100000c1f14 in main (argc=4, argv=0x7feffe3d548) at /home/simark/src/binutils-gdb/gdb/gdb.c:32
There is a target_read_memory call in sparc_supply_rwindow, whose return
value is not checked. That call fails, because inferior_ptid does not
contain a valid ptid, and uninitialized buffer contents is used.
Ultimately it results in a corrupt stop_pc.
target_ops::fetch_registers can be (and should remain, in my opinion)
independent of inferior_ptid, because the ptid of the thread from which
to fetch registers can be obtained from the regcache. In other words,
implementations of target_ops::fetch_registers should not rely on
inferior_ptid having a sensible value on entry.
The sparc64_linux_nat_target::fetch_registers case is special, because it calls
a target method that is dependent on the inferior_ptid value
(target_read_inferior, and ultimately target_ops::xfer_partial). So I would
say it's the responsibility of sparc64_linux_nat_target::fetch_registers to set
up inferior_ptid correctly prior to calling target_read_inferior.
This patch makes sparc64_linux_nat_target::fetch_registers (and
store_registers, since it works the same) temporarily set inferior_ptid. If we
ever make target_ops::xfer_partial independent of inferior_ptid, setting
inferior_ptid won't be necessary, we'll simply pass down the ptid as a
parameter in some way.
I chose to set/restore inferior_ptid in sparc_fetch_inferior_registers, because
I am not convinced that doing so in an inner location (in sparc_supply_rwindow
for instance) would always be correct. We have access to the ptid in
sparc_supply_rwindow (from the regcache), so we _could_ set inferior_ptid
there. However, I don't want to just set inferior_ptid, as that would make it
not desync'ed with `current_thread ()` and `current_inferior ()`. It's
preferable to use switch_to_thread instead, as that switches all the global
"current" stuff in a coherent way. But doing so requires a `thread_info *`,
and getting a `thread_info *` from a ptid requires a `process_stratum_target
*`. We could use `current_inferior()->process_target()` in
sparc_supply_rwindow for this (using target_read_memory uses the current
inferior's target stack anyway). However, sparc_supply_rwindow is also used in
the context of BSD uthreads, where a thread stratum target defines threads. I
presume the ptid in the regcache would be the ptid of the uthread, defined by
the thread stratum target (bsd_uthread_target). Using
`current_inferior()->process_target()` would look up a ptid defined by the
thread stratum target using the process stratum target. I don't think it would
give good results. So I prefer playing it safe and looking up the thread
earlier, in sparc_fetch_inferior_registers.
I added some assertions (in sparc_supply_rwindow and others) to verify
that the regcache's ptid matches inferior_ptid. That verifies that the
caller has properly set the correct global context. This would have
caught (though a failed assertion) the current problem.
gdb/ChangeLog:
PR gdb/27147
* sparc-nat.h (sparc_fetch_inferior_registers): Add
process_stratum_target parameter,
sparc_store_inferior_registers): update callers.
* sparc-nat.c (sparc_fetch_inferior_registers,
sparc_store_inferior_registers): Add process_stratum_target
parameter. Switch current thread before calling
sparc_supply_gregset / sparc_collect_rwindow.
(sparc_store_inferior_registers): Likewise.
* sparc-obsd-tdep.c (sparc32obsd_supply_uthread): Add assertion.
(sparc32obsd_collect_uthread): Likewise.
* sparc-tdep.c (sparc_supply_rwindow, sparc_collect_rwindow):
Add assertion.
* sparc64-obsd-tdep.c (sparc64obsd_collect_uthread,
sparc64obsd_supply_uthread): Add assertion.
Change-Id: I16c658cd70896cea604516714f7e2428fbaf4301
This commit is contained in:
Simon Marchi
parent
d4e5db4e50
commit
d1e93af64a
@ -1,3 +1,21 @@
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2021-03-04 Simon Marchi <simon.marchi@polymtl.ca>
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PR gdb/27147
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* sparc-nat.h (sparc_fetch_inferior_registers): Add
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process_stratum_target parameter,
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sparc_store_inferior_registers): update callers.
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* sparc-nat.c (sparc_fetch_inferior_registers,
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sparc_store_inferior_registers): Add process_stratum_target
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parameter. Switch current thread before calling
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sparc_supply_gregset / sparc_collect_rwindow.
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(sparc_store_inferior_registers): Likewise.
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* sparc-obsd-tdep.c (sparc32obsd_supply_uthread): Add assertion.
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(sparc32obsd_collect_uthread): Likewise.
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* sparc-tdep.c (sparc_supply_rwindow, sparc_collect_rwindow):
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Add assertion.
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* sparc64-obsd-tdep.c (sparc64obsd_collect_uthread,
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sparc64obsd_supply_uthread): Add assertion.
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2021-03-04 Tom Tromey <tromey@adacore.com>
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* ada-lang.c (struct match_data) <found_sym>: Now bool.
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@ -147,7 +147,8 @@ sparc32_fpregset_supplies_p (struct gdbarch *gdbarch, int regnum)
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for all registers (including the floating-point registers). */
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void
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sparc_fetch_inferior_registers (struct regcache *regcache, int regnum)
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sparc_fetch_inferior_registers (process_stratum_target *proc_target,
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regcache *regcache, int regnum)
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{
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struct gdbarch *gdbarch = regcache->arch ();
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ptid_t ptid = regcache->ptid ();
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@ -167,6 +168,12 @@ sparc_fetch_inferior_registers (struct regcache *regcache, int regnum)
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if (gdb_ptrace (PTRACE_GETREGS, ptid, (PTRACE_TYPE_ARG3) ®s) == -1)
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perror_with_name (_("Couldn't get registers"));
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/* Deep down, sparc_supply_rwindow reads memory, so needs the global
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thread context to be set. */
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thread_info *thread = find_thread_ptid (proc_target, ptid);
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scoped_restore_current_thread restore_thread;
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switch_to_thread (thread);
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sparc_supply_gregset (sparc_gregmap, regcache, -1, ®s);
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if (regnum != -1)
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return;
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@ -184,7 +191,8 @@ sparc_fetch_inferior_registers (struct regcache *regcache, int regnum)
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}
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void
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sparc_store_inferior_registers (struct regcache *regcache, int regnum)
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sparc_store_inferior_registers (process_stratum_target *proc_target,
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regcache *regcache, int regnum)
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{
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struct gdbarch *gdbarch = regcache->arch ();
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ptid_t ptid = regcache->ptid ();
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@ -208,6 +216,13 @@ sparc_store_inferior_registers (struct regcache *regcache, int regnum)
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ULONGEST sp;
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regcache_cooked_read_unsigned (regcache, SPARC_SP_REGNUM, &sp);
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/* Deep down, sparc_collect_rwindow writes memory, so needs the global
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thread context to be set. */
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thread_info *thread = find_thread_ptid (proc_target, ptid);
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scoped_restore_current_thread restore_thread;
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switch_to_thread (thread);
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sparc_collect_rwindow (regcache, sp, regnum);
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}
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@ -41,8 +41,10 @@ extern int (*sparc_fpregset_supplies_p) (struct gdbarch *gdbarch, int);
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extern int sparc32_gregset_supplies_p (struct gdbarch *gdbarch, int regnum);
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extern int sparc32_fpregset_supplies_p (struct gdbarch *gdbarch, int regnum);
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extern void sparc_fetch_inferior_registers (struct regcache *, int);
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extern void sparc_store_inferior_registers (struct regcache *, int);
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extern void sparc_fetch_inferior_registers (process_stratum_target *proc_target,
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regcache *, int);
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extern void sparc_store_inferior_registers (process_stratum_target *proc_target,
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regcache *, int);
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extern target_xfer_status sparc_xfer_wcookie (enum target_object object,
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const char *annex,
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@ -59,10 +61,10 @@ template<typename BaseTarget>
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struct sparc_target : public BaseTarget
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{
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void fetch_registers (struct regcache *regcache, int regnum) override
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{ sparc_fetch_inferior_registers (regcache, regnum); }
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{ sparc_fetch_inferior_registers (this, regcache, regnum); }
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void store_registers (struct regcache *regcache, int regnum) override
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{ sparc_store_inferior_registers (regcache, regnum); }
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{ sparc_store_inferior_registers (this, regcache, regnum); }
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enum target_xfer_status xfer_partial (enum target_object object,
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const char *annex,
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@ -25,6 +25,7 @@
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#include "regcache.h"
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#include "symtab.h"
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#include "trad-frame.h"
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#include "inferior.h"
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#include "obsd-tdep.h"
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#include "sparc-tdep.h"
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@ -158,6 +159,9 @@ sparc32obsd_supply_uthread (struct regcache *regcache,
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CORE_ADDR fp, fp_addr = addr + SPARC32OBSD_UTHREAD_FP_OFFSET;
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gdb_byte buf[4];
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/* This function calls functions that depend on the global current thread. */
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gdb_assert (regcache->ptid () == inferior_ptid);
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gdb_assert (regnum >= -1);
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fp = read_memory_unsigned_integer (fp_addr, 4, byte_order);
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@ -203,6 +207,9 @@ sparc32obsd_collect_uthread(const struct regcache *regcache,
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CORE_ADDR sp;
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gdb_byte buf[4];
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/* This function calls functions that depend on the global current thread. */
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gdb_assert (regcache->ptid () == inferior_ptid);
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gdb_assert (regnum >= -1);
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if (regnum == SPARC_SP_REGNUM || regnum == -1)
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@ -1948,6 +1948,9 @@ sparc_supply_rwindow (struct regcache *regcache, CORE_ADDR sp, int regnum)
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gdb_byte buf[8];
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int i;
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/* This function calls functions that depend on the global current thread. */
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gdb_assert (regcache->ptid () == inferior_ptid);
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if (sp & 1)
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{
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/* Registers are 64-bit. */
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@ -2022,6 +2025,9 @@ sparc_collect_rwindow (const struct regcache *regcache,
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gdb_byte buf[8];
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int i;
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/* This function calls functions that depend on the global current thread. */
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gdb_assert (regcache->ptid () == inferior_ptid);
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if (sp & 1)
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{
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/* Registers are 64-bit. */
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@ -35,10 +35,10 @@ class sparc64_linux_nat_target final : public linux_nat_target
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public:
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/* Add our register access methods. */
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void fetch_registers (struct regcache *regcache, int regnum) override
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{ sparc_fetch_inferior_registers (regcache, regnum); }
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{ sparc_fetch_inferior_registers (this, regcache, regnum); }
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void store_registers (struct regcache *regcache, int regnum) override
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{ sparc_store_inferior_registers (regcache, regnum); }
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{ sparc_store_inferior_registers (this, regcache, regnum); }
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/* Override linux_nat_target low methods. */
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@ -27,6 +27,7 @@
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#include "symtab.h"
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#include "objfiles.h"
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#include "trad-frame.h"
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#include "inferior.h"
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#include "obsd-tdep.h"
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#include "sparc64-tdep.h"
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@ -328,6 +329,9 @@ sparc64obsd_supply_uthread (struct regcache *regcache,
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CORE_ADDR fp, fp_addr = addr + SPARC64OBSD_UTHREAD_FP_OFFSET;
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gdb_byte buf[8];
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/* This function calls functions that depend on the global current thread. */
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gdb_assert (regcache->ptid () == inferior_ptid);
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gdb_assert (regnum >= -1);
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fp = read_memory_unsigned_integer (fp_addr, 8, byte_order);
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@ -373,6 +377,9 @@ sparc64obsd_collect_uthread(const struct regcache *regcache,
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CORE_ADDR sp;
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gdb_byte buf[8];
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/* This function calls functions that depend on the global current thread. */
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gdb_assert (regcache->ptid () == inferior_ptid);
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gdb_assert (regnum >= -1);
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||||
|
||||
if (regnum == SPARC_SP_REGNUM || regnum == -1)
|
||||
|
||||
Loading…
Reference in New Issue
Block a user