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x86/fpu: Delay instruction pointer fixup until after warning

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commit 1cec9ac2d0 upstream.

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: d5c8028b47 ("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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dave Hansen 2025-06-24 14:01:48 -07:00 committed by Greg Kroah-Hartman
parent 089d05266b
commit 4639f1d0c4
1 changed files with 2 additions and 3 deletions
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5
arch/x86/mm/extable.c
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@ -122,13 +122,12 @@ static bool ex_handler_sgx(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));
fpu_reset_from_exception_fixup();
return true;
return ex_handler_default(fixup, regs);
}
/*