gdb/arm: Remove tpidruro register from non-FreeBSD target descriptions
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linaro-tcwg-bot/tcwg_gdb_build--master-aarch64 |
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linaro-tcwg-bot/tcwg_gdb_build--master-arm |
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linaro-tcwg-bot/tcwg_gdb_check--master-arm |
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linaro-tcwg-bot/tcwg_gdb_check--master-aarch64 |
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Commit Message
Commit 92d48a1e4eac ("Add an arm-tls feature which includes the tpidruro
register from CP15.") introduced the org.gnu.gdb.arm.tls feature, which
adds the tpidruro register, and unconditionally enabled it in
aarch32_create_target_description.
In Linux, the tpidruro register isn't available via ptrace in the 32-bit
kernel but it is available for an aarch32 program running under an arm64
kernel via the ptrace compat interface. This isn't currently implemented
however, which causes GDB on arm-linux with 64-bit kernel to list the
register but show it as unavailable, as reported by Tom de Vries:
$ gdb -q -batch a.out -ex start -ex 'p $tpidruro'
Temporary breakpoint 1 at 0x512
Temporary breakpoint 1, 0xaaaaa512 in main ()
$1 = <unavailable>
Simon Marchi then clarified:
> The only time we should be seeing some "unavailable" registers or memory
> is in the context of tracepoints, for things that are not collected.
> Seeing an unavailable register here is a sign that something is not
> right.
Therefore, disable the TLS feature in aarch32 target descriptions for Linux
and NetBSD targets (the latter also doesn't seem to support accessing
tpidruro either, based on a quick look at arm-netbsd-nat.c).
This patch fixes the following tests:
Running gdb.base/inline-frame-cycle-unwind.exp ...
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 3: backtrace when the unwind is broken at frame 3
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: backtrace when the unwind is broken at frame 5
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 1: backtrace when the unwind is broken at frame 1
Tested with Ubuntu 22.04.3 on armv8l-linux-gnueabihf in native,
native-gdbserver and native-extended-gdbserver targets with no regressions.
PR tdep/31418
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31418
---
gdb/aarch32-tdep.c | 4 ++--
gdb/aarch32-tdep.h | 2 +-
gdb/aarch64-linux-nat.c | 2 +-
gdb/arch/aarch32.c | 5 +++--
gdb/arch/aarch32.h | 2 +-
gdb/arm-fbsd-tdep.c | 2 +-
gdb/arm-linux-nat.c | 2 +-
gdb/arm-linux-tdep.c | 2 +-
gdb/arm-netbsd-nat.c | 2 +-
gdbserver/linux-aarch32-tdesc.cc | 2 +-
10 files changed, 13 insertions(+), 12 deletions(-)
Comments
On 2/27/24 1:48 PM, Thiago Jung Bauermann wrote:
> Commit 92d48a1e4eac ("Add an arm-tls feature which includes the tpidruro
> register from CP15.") introduced the org.gnu.gdb.arm.tls feature, which
> adds the tpidruro register, and unconditionally enabled it in
> aarch32_create_target_description.
>
> In Linux, the tpidruro register isn't available via ptrace in the 32-bit
> kernel but it is available for an aarch32 program running under an arm64
> kernel via the ptrace compat interface. This isn't currently implemented
> however, which causes GDB on arm-linux with 64-bit kernel to list the
> register but show it as unavailable, as reported by Tom de Vries:
>
> $ gdb -q -batch a.out -ex start -ex 'p $tpidruro'
> Temporary breakpoint 1 at 0x512
>
> Temporary breakpoint 1, 0xaaaaa512 in main ()
> $1 = <unavailable>
>
> Simon Marchi then clarified:
>
>> The only time we should be seeing some "unavailable" registers or memory
>> is in the context of tracepoints, for things that are not collected.
>> Seeing an unavailable register here is a sign that something is not
>> right.
>
> Therefore, disable the TLS feature in aarch32 target descriptions for Linux
> and NetBSD targets (the latter also doesn't seem to support accessing
> tpidruro either, based on a quick look at arm-netbsd-nat.c).
>
> This patch fixes the following tests:
>
> Running gdb.base/inline-frame-cycle-unwind.exp ...
> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 3: backtrace when the unwind is broken at frame 3
> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: backtrace when the unwind is broken at frame 5
> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 1: backtrace when the unwind is broken at frame 1
>
> Tested with Ubuntu 22.04.3 on armv8l-linux-gnueabihf in native,
> native-gdbserver and native-extended-gdbserver targets with no regressions.
>
> PR tdep/31418
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31418
This looks good to me.
Approved-By: John Baldwin <jhb@FreeBSD.org>
John Baldwin <jhb@FreeBSD.org> writes:
> On 2/27/24 1:48 PM, Thiago Jung Bauermann wrote:
>> Therefore, disable the TLS feature in aarch32 target descriptions for Linux
>> and NetBSD targets (the latter also doesn't seem to support accessing
>> tpidruro either, based on a quick look at arm-netbsd-nat.c).
>> This patch fixes the following tests:
>> Running gdb.base/inline-frame-cycle-unwind.exp ...
>> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 3: backtrace when the
>> unwind is broken at frame 3
>> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: backtrace when the
>> unwind is broken at frame 5
>> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 1: backtrace when the
>> unwind is broken at frame 1
>> Tested with Ubuntu 22.04.3 on armv8l-linux-gnueabihf in native,
>> native-gdbserver and native-extended-gdbserver targets with no regressions.
>> PR tdep/31418
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31418
>
> This looks good to me.
>
> Approved-By: John Baldwin <jhb@FreeBSD.org>
Thank you for the quick review!
Unfortunately I saw an issue after I posted the patch, and just sent a
v2. Sorry about that. Fortunately, the only change is in
gdb/aarch32-tdep.c.
@@ -27,10 +27,10 @@ static struct target_desc *tdesc_aarch32;
/* See aarch32-tdep.h. */
const target_desc *
-aarch32_read_description ()
+aarch32_read_description (bool tls)
{
if (tdesc_aarch32 == nullptr)
- tdesc_aarch32 = aarch32_create_target_description ();
+ tdesc_aarch32 = aarch32_create_target_description (tls);
return tdesc_aarch32;
}
@@ -22,6 +22,6 @@ struct target_desc;
/* Get the AArch32 target description. */
-const target_desc *aarch32_read_description ();
+const target_desc *aarch32_read_description (bool tls);
#endif /* aarch32-tdep.h. */
@@ -887,7 +887,7 @@ aarch64_linux_nat_target::read_description ()
ret = ptrace (PTRACE_GETREGSET, tid, NT_ARM_VFP, &iovec);
if (ret == 0)
- return aarch32_read_description ();
+ return aarch32_read_description (false);
CORE_ADDR hwcap = linux_get_hwcap ();
CORE_ADDR hwcap2 = linux_get_hwcap2 ();
@@ -25,7 +25,7 @@
/* See aarch32.h. */
target_desc *
-aarch32_create_target_description ()
+aarch32_create_target_description (bool tls)
{
target_desc_up tdesc = allocate_target_description ();
@@ -39,7 +39,8 @@ aarch32_create_target_description ()
/* Create a vfpv3 feature, then a blank NEON feature. */
regnum = create_feature_arm_arm_vfpv3 (tdesc.get (), regnum);
tdesc_create_feature (tdesc.get (), "org.gnu.gdb.arm.neon");
- regnum = create_feature_arm_arm_tls (tdesc.get (), regnum);
+ if (tls)
+ regnum = create_feature_arm_arm_tls (tdesc.get (), regnum);
return tdesc.release ();
}
@@ -22,6 +22,6 @@
/* Create the AArch32 target description. */
-target_desc *aarch32_create_target_description ();
+target_desc *aarch32_create_target_description (bool tls);
#endif /* aarch32.h. */
@@ -228,7 +228,7 @@ arm_fbsd_read_description_auxv (const std::optional<gdb::byte_vector> &auxv,
if (arm_hwcap & HWCAP_VFP)
{
if (arm_hwcap & HWCAP_NEON)
- return aarch32_read_description ();
+ return aarch32_read_description (tls);
else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPD32))
== (HWCAP_VFPv3 | HWCAP_VFPD32))
return arm_read_description (ARM_FP_TYPE_VFPV3, tls);
@@ -568,7 +568,7 @@ arm_linux_nat_target::read_description ()
/* NEON implies VFPv3-D32 or no-VFP unit. Say that we only support
Neon with VFPv3-D32. */
if (arm_hwcap & HWCAP_NEON)
- return aarch32_read_description ();
+ return aarch32_read_description (false);
else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPv3D16)) == HWCAP_VFPv3)
return arm_read_description (ARM_FP_TYPE_VFPV3, false);
@@ -740,7 +740,7 @@ arm_linux_core_read_description (struct gdbarch *gdbarch,
/* NEON implies VFPv3-D32 or no-VFP unit. Say that we only support
Neon with VFPv3-D32. */
if (arm_hwcap & HWCAP_NEON)
- return aarch32_read_description ();
+ return aarch32_read_description (false);
else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPv3D16)) == HWCAP_VFPv3)
return arm_read_description (ARM_FP_TYPE_VFPV3, false);
@@ -350,7 +350,7 @@ arm_netbsd_nat_target::read_description ()
len = sizeof(flag);
if (sysctlbyname("machdep.neon_present", &flag, &len, NULL, 0) == 0 && flag)
- return aarch32_read_description ();
+ return aarch32_read_description (false);
return arm_read_description (ARM_FP_TYPE_VFPV3, false);
}
@@ -32,7 +32,7 @@ aarch32_linux_read_description ()
{
if (tdesc_aarch32 == nullptr)
{
- tdesc_aarch32 = aarch32_create_target_description ();
+ tdesc_aarch32 = aarch32_create_target_description (false);
static const char *expedite_regs[] = { "r11", "sp", "pc", 0 };
init_target_desc (tdesc_aarch32, expedite_regs);