[PATCH 5.15.y] x86/fpu: Delay instruction pointer fixup until after warning

[Sasha Levin <sashal@kernel.org>]

From: Dave Hansen <dave.hansen@linux.intel.com>

[ Upstream commit 1cec9ac2d071cfd2da562241aab0ef701355762a ]

Right now, if XRSTOR fails a console message like this is be printed:

	Bad FPU state detected at restore_fpregs_from_fpstate+0x9a/0x170, reinitializing FPU registers.

However, the text location (...+0x9a in this case) is the instruction
*AFTER* the XRSTOR. The highlighted instruction in the "Code:" dump
also points one instruction late.

The reason is that the "fixup" moves RIP up to pass the bad XRSTOR and
keep on running after returning from the #GP handler. But it does this
fixup before warning.

The resulting warning output is nonsensical because it looks like the
non-FPU-related instruction is #GP'ing.

Do not fix up RIP until after printing the warning. Do this by using
the more generic and standard ex_handler_default().

Fixes: d5c8028b4788 ("x86/fpu: Reinitialize FPU registers if restoring FPU state fails")
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Acked-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250624210148.97126F9E%40davehans-spike.ostc.intel.com
[ Replace fpu_reset_from_exception_fixup() with __restore_fpregs_from_fpstate() ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/mm/extable.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index a9c7efd4b794..cba212d7146a 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -60,13 +60,12 @@ static bool ex_handler_fault(const struct exception_table_entry *fixup,
 static bool ex_handler_fprestore(const struct exception_table_entry *fixup,
 				 struct pt_regs *regs)
 {
-	regs->ip = ex_fixup_addr(fixup);
-
 	WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.",
 		  (void *)instruction_pointer(regs));
 
 	__restore_fpregs_from_fpstate(&init_fpstate, xfeatures_mask_fpstate());
-	return true;
+
+	return ex_handler_default(fixup, regs);
 }
 
 static bool ex_handler_uaccess(const struct exception_table_entry *fixup,
-- 
2.39.5