2020-03-05 09:34:56

by Yu Chen

Subject: [PATCH] x86/cpuid: Use macro instead of number in cpuid_read()

Make and use macro CHUNK_SIZE, instead of numeric value 16 in
cpuid_read().

Signed-off-by: Yu Chen <[email protected]>
---
arch/x86/kernel/cpuid.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 3492aa36b..f7d7e0ef7 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -48,6 +48,9 @@ struct cpuid_regs_done {
struct completion done;
};

+/* cpuid must be read in chunks of 16 bytes */
+#define CHUNK_SIZE 16
+
static void cpuid_smp_cpuid(void *cmd_block)
{
struct cpuid_regs_done *cmd = cmd_block;
@@ -69,11 +72,11 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
ssize_t bytes = 0;
int err = 0;

- if (count % 16)
+ if (count % CHUNK_SIZE)
return -EINVAL; /* Invalid chunk size */

init_completion(&cmd.done);
- for (; count; count -= 16) {
+ for (; count; count -= CHUNK_SIZE) {
call_single_data_t csd = {
.func = cpuid_smp_cpuid,
.info = &cmd,
@@ -86,12 +89,12 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
if (err)
break;
wait_for_completion(&cmd.done);
- if (copy_to_user(tmp, &cmd.regs, 16)) {
+ if (copy_to_user(tmp, &cmd.regs, CHUNK_SIZE)) {
err = -EFAULT;
break;
}
- tmp += 16;
- bytes += 16;
+ tmp += CHUNK_SIZE;
+ bytes += CHUNK_SIZE;
*ppos = ++pos;
reinit_completion(&cmd.done);
}
--
2.17.1

2020-03-05 09:53:11

by H. Peter Anvin

Subject: Re: [PATCH] x86/cpuid: Use macro instead of number in cpuid_read()

On March 5, 2020 1:33:18 AM PST, Yu Chen <[email protected]> wrote:
>Make and use macro CHUNK_SIZE, instead of numeric value 16 in
>cpuid_read().
>
>Signed-off-by: Yu Chen <[email protected]>
>---
> arch/x86/kernel/cpuid.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
>diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
>index 3492aa36b..f7d7e0ef7 100644
>--- a/arch/x86/kernel/cpuid.c
>+++ b/arch/x86/kernel/cpuid.c
>@@ -48,6 +48,9 @@ struct cpuid_regs_done {
> struct completion done;
> };
>
>+/* cpuid must be read in chunks of 16 bytes */
>+#define CHUNK_SIZE 16
>+
> static void cpuid_smp_cpuid(void *cmd_block)
> {
> struct cpuid_regs_done *cmd = cmd_block;
>@@ -69,11 +72,11 @@ static ssize_t cpuid_read(struct file *file, char
>__user *buf,
> ssize_t bytes = 0;
> int err = 0;
>
>- if (count % 16)
>+ if (count % CHUNK_SIZE)
> return -EINVAL; /* Invalid chunk size */
>
> init_completion(&cmd.done);
>- for (; count; count -= 16) {
>+ for (; count; count -= CHUNK_SIZE) {
> call_single_data_t csd = {
> .func = cpuid_smp_cpuid,
> .info = &cmd,
>@@ -86,12 +89,12 @@ static ssize_t cpuid_read(struct file *file, char
>__user *buf,
> if (err)
> break;
> wait_for_completion(&cmd.done);
>- if (copy_to_user(tmp, &cmd.regs, 16)) {
>+ if (copy_to_user(tmp, &cmd.regs, CHUNK_SIZE)) {
> err = -EFAULT;
> break;
> }
>- tmp += 16;
>- bytes += 16;
>+ tmp += CHUNK_SIZE;
>+ bytes += CHUNK_SIZE;
> *ppos = ++pos;
> reinit_completion(&cmd.done);
> }

It would make more sense to define a structure and add it to a uapi header.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.