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Subject[PATCH] um: Fix check for _xstate for older hosts
Commit 0a987645672e ("um: Allow building and running on older
hosts") attempted to check for PTRACE_{GET,SET}REGSET under the premise
that these ptrace(2) parameters were directly linked with the presence
of the _xstate structure.

After Richard's commit 61e8d462457f ("um: Correctly check for
PTRACE_GETRESET/SETREGSET") which properly included linux/ptrace.h
instead of asm/ptrace.h, we could get into the original build failure
that I reported:

arch/x86/um/user-offsets.c: In function 'foo':
arch/x86/um/user-offsets.c:54: error: invalid application of 'sizeof' to
incomplete type 'struct _xstate'

On this particular host, we do have PTRACE_GETREGSET and
PTRACE_SETREGSET defined in linux/ptrace.h, but not the structure
_xstate that should be pulled from the following include chain: signal.h
-> bits/sigcontext.h.

Correctly fix this by checking for FP_XSTATE_MAGIC1 which is the correct
way to see if struct _xstate is available or not on the host.

Fixes: 61e8d462457f ("um: Correctly check for PTRACE_GETRESET/SETREGSET")
Fixes: 0a987645672e ("um: Allow building and running on older hosts")
Signed-off-by: Florian Fainelli <>
arch/x86/um/user-offsets.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index ae4cd58c0c7a..02250b2633b8 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -50,7 +50,7 @@ void foo(void)
DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long));
DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long));
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