[PATCH] ACPI: OSL: Fix and clean up acpi_os_read/write_port()

From: Rafael J. Wysocki
Date: Wed Jan 12 2022 - 13:32:03 EST


From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

First, remove type casts that make acpi_os_read_port() only work on
little endian and are generally not needed.

Second, avoid clearing the memory pointed to by the value return
pointer in acpi_os_read_port() if it is the dummy on the stack (in
which case clearing it is not necessary).

Finally, prevent both acpi_os_read_port() and acpi_os_write_port()
from crashing the kernel when they receive an unsupported width
value and make them print a debug message and return an error instead.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/acpi/osl.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

Index: linux-pm/drivers/acpi/osl.c
===================================================================
--- linux-pm.orig/drivers/acpi/osl.c
+++ linux-pm/drivers/acpi/osl.c
@@ -642,22 +642,24 @@ u64 acpi_os_get_timer(void)
(ACPI_100NSEC_PER_SEC / HZ);
}

-acpi_status acpi_os_read_port(acpi_io_address port, u32 * value, u32 width)
+acpi_status acpi_os_read_port(acpi_io_address port, u32 *value, u32 width)
{
u32 dummy;

- if (!value)
+ if (value)
+ *value = 0;
+ else
value = &dummy;

- *value = 0;
if (width <= 8) {
- *(u8 *) value = inb(port);
+ *value = inb(port);
} else if (width <= 16) {
- *(u16 *) value = inw(port);
+ *value = inw(port);
} else if (width <= 32) {
- *(u32 *) value = inl(port);
+ *value = inl(port);
} else {
- BUG();
+ pr_debug("%s: Access width %d not supported\n", __func__, width);
+ return AE_BAD_PARAMETER;
}

return AE_OK;
@@ -674,7 +676,8 @@ acpi_status acpi_os_write_port(acpi_io_a
} else if (width <= 32) {
outl(value, port);
} else {
- BUG();
+ pr_debug("%s: Access width %d not supported\n", __func__, width);
+ return AE_BAD_PARAMETER;
}

return AE_OK;