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arm64: fpsimd: Fix type mismatch in sve_{save,load}_state()

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commit ae24f6b06e upstream.

The sve_save_state() and sve_load_state() functions take a 32-bit int
argument that describes whether to save/restore the FFR. Their assembly
implementations consume the entire 64-bit register containing this
32-bit value, and will attempt to save/restore the FFR if any bit of
that 64-bit register is non-zero.

Per the AAPCS64 parameter passing rules, the callee is responsible for
any necessary widening, and the upper 32-bits are permitted to contain
arbitrary values. If the upper 32 bits are non-zero, this could result
in an unexpected attempt to save/restore the FFR, and consequently could
lead to unexpected traps/undefs/faults.

In practice compilers are very unlikely to generate code where the upper
32-bits would be non-zero, but they are permitted to do so.

Fix this by only consuming the low 32 bits of the register, and update
comments accordingly.

The hyp code __sve_save_state() and __sve_restore_state() functions
don't have the same latent bug as they override the full 64-bit register
containing the argument.

Fixes: 9f58486657 ("arm64/sve: Make access to FFR optional")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oliver Upton <oupton@kernel.org>
Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mark Rutland
2026-07-24 15:54:58 +02:00
committed by Greg Kroah-Hartman
parent 8c8818e52f
commit 193d669c7a
1 changed files with 4 additions and 4 deletions
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arch/arm64/kernel/entry-fpsimd.S
+4 -4
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@@ -38,10 +38,10 @@ SYM_FUNC_END(fpsimd_load_state)
*
* x0 - pointer to buffer for state
* x1 - pointer to storage for FPSR
* x2 - Save FFR if non-zero
* w2 - Save FFR if non-zero
*/
SYM_FUNC_START(sve_save_state)
sve_save 0, x1, x2, 3
sve_save 0, x1, w2, 3
ret
SYM_FUNC_END(sve_save_state)
@@ -50,10 +50,10 @@ SYM_FUNC_END(sve_save_state)
*
* x0 - pointer to buffer for state
* x1 - pointer to storage for FPSR
* x2 - Restore FFR if non-zero
* w2 - Restore FFR if non-zero
*/
SYM_FUNC_START(sve_load_state)
sve_load 0, x1, x2, 4
sve_load 0, x1, w2, 4
ret
SYM_FUNC_END(sve_load_state)