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drivers: meson: sm: correct meson_sm_* API retval handling 

1. Following the ARM SMC32 calling convention, the return value
from secure monitor is a 32-bit signed integer. This patch changes
the type of the return value of the function meson_sm_call().

2. Now, when meson_sm_call() returns a 32-bit signed integer, we need
to ensure that this value is not negative. It is important to check
that the return value is not negative in both the meson_sm_call_read()
and meson_sm_call_write() functions.

3. Add a comment explaining why it is necessary to check if the SMC
return value is equal to 0 in the function meson_sm_call_read().
It is not obvious when reading this code.

Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230830140850.17130-1-avromanov@salutedevices.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
This commit is contained in:
Alexey Romanov 2023-08-30 17:08:50 +03:00 committed by Neil Armstrong
parent 0bb80ecc33
commit 0d423c4a78
2 changed files with 14 additions and 8 deletions
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20
drivers/firmware/meson/meson_sm.c
View File

@ -67,7 +67,7 @@ static u32 meson_sm_get_cmd(const struct meson_sm_chip *chip,
return cmd->smc_id;
}
static u32 __meson_sm_call(u32 cmd, u32 arg0, u32 arg1, u32 arg2,
static s32 __meson_sm_call(u32 cmd, u32 arg0, u32 arg1, u32 arg2,
u32 arg3, u32 arg4)
{
struct arm_smccc_res res;
@ -102,9 +102,10 @@ static void __iomem *meson_sm_map_shmem(u32 cmd_shmem, unsigned int size)
* Return: 0 on success, a negative value on error
*/
int meson_sm_call(struct meson_sm_firmware *fw, unsigned int cmd_index,
u32 *ret, u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
s32 *ret, u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
{
u32 cmd, lret;
u32 cmd;
s32 lret;
if (!fw->chip)
return -ENOENT;
@ -143,7 +144,7 @@ int meson_sm_call_read(struct meson_sm_firmware *fw, void *buffer,
unsigned int bsize, unsigned int cmd_index, u32 arg0,
u32 arg1, u32 arg2, u32 arg3, u32 arg4)
{
u32 size;
s32 size;
int ret;
if (!fw->chip)
@ -158,11 +159,16 @@ int meson_sm_call_read(struct meson_sm_firmware *fw, void *buffer,
if (meson_sm_call(fw, cmd_index, &size, arg0, arg1, arg2, arg3, arg4) < 0)
return -EINVAL;
if (size > bsize)
if (size < 0 || size > bsize)
return -EINVAL;
ret = size;
/* In some cases (for example GET_CHIP_ID command),
* SMC doesn't return the number of bytes read, even
* though the bytes were actually read into sm_shmem_out.
* So this check is needed.
*/
if (!size)
size = bsize;
@ -192,7 +198,7 @@ int meson_sm_call_write(struct meson_sm_firmware *fw, void *buffer,
unsigned int size, unsigned int cmd_index, u32 arg0,
u32 arg1, u32 arg2, u32 arg3, u32 arg4)
{
u32 written;
s32 written;
if (!fw->chip)
return -ENOENT;
@ -208,7 +214,7 @@ int meson_sm_call_write(struct meson_sm_firmware *fw, void *buffer,
if (meson_sm_call(fw, cmd_index, &written, arg0, arg1, arg2, arg3, arg4) < 0)
return -EINVAL;
if (!written)
if (written <= 0 || written > size)
return -EINVAL;
return written;

2
include/linux/firmware/meson/meson_sm.h
View File

@ -19,7 +19,7 @@ enum {
struct meson_sm_firmware;
int meson_sm_call(struct meson_sm_firmware *fw, unsigned int cmd_index,
u32 *ret, u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4);
s32 *ret, u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4);
int meson_sm_call_write(struct meson_sm_firmware *fw, void *buffer,
unsigned int b_size, unsigned int cmd_index, u32 arg0,
u32 arg1, u32 arg2, u32 arg3, u32 arg4);