169 lines
5.5 KiB
Diff
169 lines
5.5 KiB
Diff
From 1cd845ab3d405412aabf9b959aa527dd60143826 Mon Sep 17 00:00:00 2001
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From: Tom de Vries <tdevries@suse.de>
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Date: Thu, 2 Nov 2023 14:51:02 +0100
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Subject: [PATCH] [gdb] Fix segfault in for_each_block, part 2
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The previous commit describes PR gdb/30547, a segfault when running test-case
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gdb.base/vfork-follow-parent.exp on powerpc64 (likewise on s390x).
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The root cause for the segmentation fault is that linux_is_uclinux gives an
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incorrect result: it returns true instead of false.
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So, why does linux_is_uclinux:
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...
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int
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linux_is_uclinux (void)
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{
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CORE_ADDR dummy;
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return (target_auxv_search (AT_NULL, &dummy) > 0
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&& target_auxv_search (AT_PAGESZ, &dummy) == 0);
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...
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return true?
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This is because ppc_linux_target_wordsize returns 4 instead of 8, causing
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ppc_linux_nat_target::auxv_parse to misinterpret the auxv vector.
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So, why does ppc_linux_target_wordsize:
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...
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int
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ppc_linux_target_wordsize (int tid)
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{
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int wordsize = 4;
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/* Check for 64-bit inferior process. This is the case when the host is
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64-bit, and in addition the top bit of the MSR register is set. */
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long msr;
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errno = 0;
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msr = (long) ptrace (PTRACE_PEEKUSER, tid, PT_MSR * 8, 0);
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if (errno == 0 && ppc64_64bit_inferior_p (msr))
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wordsize = 8;
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return wordsize;
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}
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...
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return 4?
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Specifically, we get this result because because tid == 0, so we get
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errno == ESRCH.
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The tid == 0 is caused by the switch_to_no_thread in
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handle_vfork_child_exec_or_exit:
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...
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/* Switch to no-thread while running clone_program_space, so
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that clone_program_space doesn't want to read the
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selected frame of a dead process. */
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scoped_restore_current_thread restore_thread;
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switch_to_no_thread ();
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inf->pspace = new program_space (maybe_new_address_space ());
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...
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but moving the maybe_new_address_space call to before that gives us the
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same result. The tid is no longer 0, but we still get ESRCH because the
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thread has exited.
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Fix this in handle_vfork_child_exec_or_exit by doing the
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maybe_new_address_space call in the context of the vfork parent.
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Tested on top of trunk on x86_64-linux and ppc64le-linux.
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Tested on top of gdb-14-branch on ppc64-linux.
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Co-Authored-By: Simon Marchi <simon.marchi@polymtl.ca>
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PR gdb/30547
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Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30547
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---
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gdb/infrun.c | 16 +++++++++++-----
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gdb/nat/ppc-linux.c | 2 ++
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gdb/ppc-linux-nat.c | 2 ++
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gdb/s390-linux-nat.c | 5 ++++-
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4 files changed, 19 insertions(+), 6 deletions(-)
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diff --git a/gdb/infrun.c b/gdb/infrun.c
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index 9c1b1f04e4d..c078098a6f8 100644
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--- a/gdb/infrun.c
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+++ b/gdb/infrun.c
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@@ -1014,13 +1014,19 @@ handle_vfork_child_exec_or_exit (int exec)
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go ahead and create a new one for this exiting
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inferior. */
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- /* Switch to no-thread while running clone_program_space, so
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- that clone_program_space doesn't want to read the
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- selected frame of a dead process. */
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scoped_restore_current_thread restore_thread;
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- switch_to_no_thread ();
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- inf->pspace = new program_space (maybe_new_address_space ());
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+ /* Temporarily switch to the vfork parent, to facilitate ptrace
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+ calls done during maybe_new_address_space. */
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+ switch_to_thread (any_live_thread_of_inferior (vfork_parent));
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+ address_space *aspace = maybe_new_address_space ();
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+
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+ /* Switch back to the vfork child inferior. Switch to no-thread
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+ while running clone_program_space, so that clone_program_space
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+ doesn't want to read the selected frame of a dead process. */
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+ switch_to_inferior_no_thread (inf);
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+
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+ inf->pspace = new program_space (aspace);
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inf->aspace = inf->pspace->aspace;
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set_current_program_space (inf->pspace);
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inf->removable = true;
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diff --git a/gdb/nat/ppc-linux.c b/gdb/nat/ppc-linux.c
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index 0957d1b58a7..74549754806 100644
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--- a/gdb/nat/ppc-linux.c
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+++ b/gdb/nat/ppc-linux.c
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@@ -78,6 +78,8 @@ ppc64_64bit_inferior_p (long msr)
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int
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ppc_linux_target_wordsize (int tid)
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{
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+ gdb_assert (tid != 0);
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+
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int wordsize = 4;
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/* Check for 64-bit inferior process. This is the case when the host is
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diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
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index d8a8fbdf706..500fb566bc1 100644
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--- a/gdb/ppc-linux-nat.c
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+++ b/gdb/ppc-linux-nat.c
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@@ -1918,6 +1918,8 @@ ppc_linux_nat_target::auxv_parse (const gdb_byte **readptr,
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const gdb_byte *endptr, CORE_ADDR *typep,
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CORE_ADDR *valp)
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{
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+ gdb_assert (inferior_ptid != null_ptid);
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+
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int tid = inferior_ptid.lwp ();
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if (tid == 0)
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tid = inferior_ptid.pid ();
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diff --git a/gdb/s390-linux-nat.c b/gdb/s390-linux-nat.c
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index fc3917d30be..403f37d690d 100644
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--- a/gdb/s390-linux-nat.c
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+++ b/gdb/s390-linux-nat.c
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@@ -949,10 +949,12 @@ s390_target_wordsize (void)
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/* Check for 64-bit inferior process. This is the case when the host is
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64-bit, and in addition bit 32 of the PSW mask is set. */
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#ifdef __s390x__
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+ int tid = s390_inferior_tid ();
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+ gdb_assert (tid != 0);
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long pswm;
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errno = 0;
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- pswm = (long) ptrace (PTRACE_PEEKUSER, s390_inferior_tid (), PT_PSWMASK, 0);
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+ pswm = (long) ptrace (PTRACE_PEEKUSER, tid, PT_PSWMASK, 0);
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if (errno == 0 && (pswm & 0x100000000ul) != 0)
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wordsize = 8;
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#endif
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@@ -965,6 +967,7 @@ s390_linux_nat_target::auxv_parse (const gdb_byte **readptr,
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const gdb_byte *endptr, CORE_ADDR *typep,
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CORE_ADDR *valp)
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{
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+ gdb_assert (inferior_ptid != null_ptid);
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int sizeof_auxv_field = s390_target_wordsize ();
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enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
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const gdb_byte *ptr = *readptr;
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base-commit: 59053f06bd94be51efacfa80f9a1f738e3e1ee9c
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--
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2.35.3
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