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author | Tom de Vries <tdevries@suse.de> | 2019-09-24 23:38:49 +0200 |
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committer | Tom de Vries <tdevries@suse.de> | 2019-09-24 23:38:49 +0200 |
commit | 3d4352200e3e98a6d8855e6f3a39b6d33d84e36b (patch) | |
tree | b125a52bc79b11576a7a16a5232536e804504f91 /gdb/solib-legacy.c | |
parent | e8f8842d90abe5eafa8c32f08fbc3a747a45747c (diff) | |
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[gdb/tdep] Handle mxcsr kernel bug on Intel Skylake CPUs
On my openSUSE Leap 15.1 x86_64 Skylake system with the default (4.12) kernel,
I run into:
...
FAIL: gdb.base/gcore.exp: corefile restored all registers
...
The problem is that there's a difference in the mxcsr register value before
and after the gcore command:
...
- mxcsr 0x0 [ ]
+ mxcsr 0x400440 [ DAZ OM ]
...
This can be traced back to amd64_linux_nat_target::fetch_registers, where
xstateregs is partially initialized by the ptrace call:
...
char xstateregs[X86_XSTATE_MAX_SIZE];
struct iovec iov;
amd64_collect_xsave (regcache, -1, xstateregs, 0);
iov.iov_base = xstateregs;
iov.iov_len = sizeof (xstateregs);
if (ptrace (PTRACE_GETREGSET, tid,
(unsigned int) NT_X86_XSTATE, (long) &iov) < 0)
perror_with_name (_("Couldn't get extended state status"));
amd64_supply_xsave (regcache, -1, xstateregs);
...
after which amd64_supply_xsave is called.
The amd64_supply_xsave call is supposed to only use initialized parts of
xstateregs, but due to a kernel bug on intel skylake (fixed from 4.14 onwards
by commit 0852b374173b "x86/fpu: Add FPU state copying quirk to handle XRSTOR
failure on Intel Skylake CPUs") it can happen that the mxcsr part of
xstateregs is not initialized, while amd64_supply_xsave expects it to be
initialized, which explains the FAIL mentioned above.
Fix the undetermined behaviour by initializing xstateregs before calling
ptrace, which makes sure we get a 0x0 for mxcsr when this kernel bug occurs,
and which also happens to fix the FAIL.
Furthermore, add an xfail for this FAIL which triggers the same kernel bug:
...
FAIL: gdb.arch/amd64-init-x87-values.exp: check_setting_mxcsr_before_enable: \
check new value of MXCSR is still in place
...
Both FAILs pass when using a 5.3 kernel instead on the system mentioned above.
Tested on x86_64-linux.
gdb/ChangeLog:
2019-09-24 Tom de Vries <tdevries@suse.de>
PR gdb/23815
* amd64-linux-nat.c (amd64_linux_nat_target::fetch_registers):
Initialize xstateregs before ptrace PTRACE_GETREGSET call.
gdb/testsuite/ChangeLog:
2019-09-24 Tom de Vries <tdevries@suse.de>
PR gdb/24598
* gdb.arch/amd64-init-x87-values.exp: Add xfail.
Diffstat (limited to 'gdb/solib-legacy.c')
0 files changed, 0 insertions, 0 deletions