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Subject[PATCH 2/2] cdrom: reduce stack usage of mmc_ioctl_dvd_read_struct
1. kmalloc 192 bytes in dvd_read_bca (which is inlined into dvd_read_struct)
2. Pass struct packet_command to all dvd_read_* functions.

Checkstack output:
Before: mmc_ioctl_dvd_read_struct: 280
After: mmc_ioctl_dvd_read_struct: 56

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
---
drivers/cdrom/cdrom.c | 139 +++++++++++++++++++++++++++----------------------
1 files changed, 77 insertions(+), 62 deletions(-)

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index eb6f6ad..7946653 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -1712,29 +1712,30 @@ static int dvd_do_auth(struct cdrom_device_info *cdi, dvd_authinfo *ai)
return 0;
}

-static int dvd_read_physical(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_physical(struct cdrom_device_info *cdi, dvd_struct *s,
+ struct packet_command *cgc)
{
unsigned char buf[21], *base;
struct dvd_layer *layer;
- struct packet_command cgc;
struct cdrom_device_ops *cdo = cdi->ops;
int ret, layer_num = s->physical.layer_num;

if (layer_num >= DVD_LAYERS)
return -EINVAL;

- init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
- cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
- cgc.cmd[6] = layer_num;
- cgc.cmd[7] = s->type;
- cgc.cmd[9] = cgc.buflen & 0xff;
+ init_cdrom_command(cgc, buf, sizeof(buf), CGC_DATA_READ);
+ cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+ cgc->cmd[6] = layer_num;
+ cgc->cmd[7] = s->type;
+ cgc->cmd[9] = cgc->buflen & 0xff;

/*
* refrain from reporting errors on non-existing layers (mainly)
*/
- cgc.quiet = 1;
+ cgc->quiet = 1;

- if ((ret = cdo->generic_packet(cdi, &cgc)))
+ ret = cdo->generic_packet(cdi, cgc);
+ if (ret)
return ret;

base = &buf[4];
@@ -1762,21 +1763,22 @@ static int dvd_read_physical(struct cdrom_device_info *cdi, dvd_struct *s)
return 0;
}

-static int dvd_read_copyright(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_copyright(struct cdrom_device_info *cdi, dvd_struct *s,
+ struct packet_command *cgc)
{
int ret;
u_char buf[8];
- struct packet_command cgc;
struct cdrom_device_ops *cdo = cdi->ops;

- init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
- cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
- cgc.cmd[6] = s->copyright.layer_num;
- cgc.cmd[7] = s->type;
- cgc.cmd[8] = cgc.buflen >> 8;
- cgc.cmd[9] = cgc.buflen & 0xff;
+ init_cdrom_command(cgc, buf, sizeof(buf), CGC_DATA_READ);
+ cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+ cgc->cmd[6] = s->copyright.layer_num;
+ cgc->cmd[7] = s->type;
+ cgc->cmd[8] = cgc->buflen >> 8;
+ cgc->cmd[9] = cgc->buflen & 0xff;

- if ((ret = cdo->generic_packet(cdi, &cgc)))
+ ret = cdo->generic_packet(cdi, cgc);
+ if (ret)
return ret;

s->copyright.cpst = buf[4];
@@ -1785,79 +1787,89 @@ static int dvd_read_copyright(struct cdrom_device_info *cdi, dvd_struct *s)
return 0;
}

-static int dvd_read_disckey(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_disckey(struct cdrom_device_info *cdi, dvd_struct *s,
+ struct packet_command *cgc)
{
int ret, size;
u_char *buf;
- struct packet_command cgc;
struct cdrom_device_ops *cdo = cdi->ops;

size = sizeof(s->disckey.value) + 4;

- if ((buf = kmalloc(size, GFP_KERNEL)) == NULL)
+ buf = kmalloc(size, GFP_KERNEL);
+ if (!buf)
return -ENOMEM;

- init_cdrom_command(&cgc, buf, size, CGC_DATA_READ);
- cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
- cgc.cmd[7] = s->type;
- cgc.cmd[8] = size >> 8;
- cgc.cmd[9] = size & 0xff;
- cgc.cmd[10] = s->disckey.agid << 6;
+ init_cdrom_command(cgc, buf, size, CGC_DATA_READ);
+ cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+ cgc->cmd[7] = s->type;
+ cgc->cmd[8] = size >> 8;
+ cgc->cmd[9] = size & 0xff;
+ cgc->cmd[10] = s->disckey.agid << 6;

- if (!(ret = cdo->generic_packet(cdi, &cgc)))
+ ret = cdo->generic_packet(cdi, cgc);
+ if (!ret)
memcpy(s->disckey.value, &buf[4], sizeof(s->disckey.value));

kfree(buf);
return ret;
}

-static int dvd_read_bca(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_bca(struct cdrom_device_info *cdi, dvd_struct *s,
+ struct packet_command *cgc)
{
- int ret;
- u_char buf[4 + 188];
- struct packet_command cgc;
+ int ret, size = 4 + 188;
+ u_char *buf;
struct cdrom_device_ops *cdo = cdi->ops;

- init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
- cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
- cgc.cmd[7] = s->type;
- cgc.cmd[9] = cgc.buflen & 0xff;
+ buf = kmalloc(size, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;

- if ((ret = cdo->generic_packet(cdi, &cgc)))
- return ret;
+ init_cdrom_command(cgc, buf, size, CGC_DATA_READ);
+ cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+ cgc->cmd[7] = s->type;
+ cgc->cmd[9] = cgc->buflen & 0xff;
+
+ ret = cdo->generic_packet(cdi, cgc);
+ if (ret)
+ goto out;

s->bca.len = buf[0] << 8 | buf[1];
if (s->bca.len < 12 || s->bca.len > 188) {
cdinfo(CD_WARNING, "Received invalid BCA length (%d)\n", s->bca.len);
- return -EIO;
+ ret = -EIO;
+ goto out;
}
memcpy(s->bca.value, &buf[4], s->bca.len);
-
- return 0;
+ ret = 0;
+out:
+ kfree(buf);
+ return ret;
}

-static int dvd_read_manufact(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_manufact(struct cdrom_device_info *cdi, dvd_struct *s,
+ struct packet_command *cgc)
{
int ret = 0, size;
u_char *buf;
- struct packet_command cgc;
struct cdrom_device_ops *cdo = cdi->ops;

size = sizeof(s->manufact.value) + 4;

- if ((buf = kmalloc(size, GFP_KERNEL)) == NULL)
+ buf = kmalloc(size, GFP_KERNEL);
+ if (!buf)
return -ENOMEM;

- init_cdrom_command(&cgc, buf, size, CGC_DATA_READ);
- cgc.cmd[0] = GPCMD_READ_DVD_STRUCTURE;
- cgc.cmd[7] = s->type;
- cgc.cmd[8] = size >> 8;
- cgc.cmd[9] = size & 0xff;
+ init_cdrom_command(cgc, buf, size, CGC_DATA_READ);
+ cgc->cmd[0] = GPCMD_READ_DVD_STRUCTURE;
+ cgc->cmd[7] = s->type;
+ cgc->cmd[8] = size >> 8;
+ cgc->cmd[9] = size & 0xff;

- if ((ret = cdo->generic_packet(cdi, &cgc))) {
- kfree(buf);
- return ret;
- }
+ ret = cdo->generic_packet(cdi, cgc);
+ if (ret)
+ goto out;

s->manufact.len = buf[0] << 8 | buf[1];
if (s->manufact.len < 0 || s->manufact.len > 2048) {
@@ -1868,27 +1880,29 @@ static int dvd_read_manufact(struct cdrom_device_info *cdi, dvd_struct *s)
memcpy(s->manufact.value, &buf[4], s->manufact.len);
}

+out:
kfree(buf);
return ret;
}

-static int dvd_read_struct(struct cdrom_device_info *cdi, dvd_struct *s)
+static int dvd_read_struct(struct cdrom_device_info *cdi, dvd_struct *s,
+ struct packet_command *cgc)
{
switch (s->type) {
case DVD_STRUCT_PHYSICAL:
- return dvd_read_physical(cdi, s);
+ return dvd_read_physical(cdi, s, cgc);

case DVD_STRUCT_COPYRIGHT:
- return dvd_read_copyright(cdi, s);
+ return dvd_read_copyright(cdi, s, cgc);

case DVD_STRUCT_DISCKEY:
- return dvd_read_disckey(cdi, s);
+ return dvd_read_disckey(cdi, s, cgc);

case DVD_STRUCT_BCA:
- return dvd_read_bca(cdi, s);
+ return dvd_read_bca(cdi, s, cgc);

case DVD_STRUCT_MANUFACT:
- return dvd_read_manufact(cdi, s);
+ return dvd_read_manufact(cdi, s, cgc);

default:
cdinfo(CD_WARNING, ": Invalid DVD structure read requested (%d)\n",
@@ -3023,7 +3037,8 @@ static noinline int mmc_ioctl_cdrom_pause_resume(struct cdrom_device_info *cdi,
}

static noinline int mmc_ioctl_dvd_read_struct(struct cdrom_device_info *cdi,
- void __user *arg)
+ void __user *arg,
+ struct packet_command *cgc)
{
int ret;
dvd_struct *s;
@@ -3042,7 +3057,7 @@ static noinline int mmc_ioctl_dvd_read_struct(struct cdrom_device_info *cdi,
return -EFAULT;
}

- ret = dvd_read_struct(cdi, s);
+ ret = dvd_read_struct(cdi, s, cgc);
if (ret)
goto out;

@@ -3128,7 +3143,7 @@ static int mmc_ioctl(struct cdrom_device_info *cdi, unsigned int cmd,
case CDROMRESUME:
return mmc_ioctl_cdrom_pause_resume(cdi, &cgc, cmd);
case DVD_READ_STRUCT:
- return mmc_ioctl_dvd_read_struct(cdi, userptr);
+ return mmc_ioctl_dvd_read_struct(cdi, userptr, &cgc);
case DVD_AUTH:
return mmc_ioctl_dvd_auth(cdi, userptr);
case CDROM_NEXT_WRITABLE:
--
1.5.6.4


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