* [PATCH] [RESEND] firmware: tegra: reduce stack usage
@ 2021-09-27 12:41 Arnd Bergmann
2021-10-07 18:11 ` Thierry Reding
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2021-09-27 12:41 UTC (permalink / raw)
To: Thierry Reding, Jonathan Hunter; +Cc: Arnd Bergmann, linux-tegra, linux-kernel
From: Arnd Bergmann <arnd@arndb.de>
Building the bpmp-debugfs driver for Arm results in a warning for stack usage:
drivers/firmware/tegra/bpmp-debugfs.c:321:16: error: stack frame size of 1224 bytes in function 'bpmp_debug_store' [-Werror,-Wframe-larger-than=]
static ssize_t bpmp_debug_store(struct file *file, const char __user *buf,
It should be possible to rearrange the code to not require two separate
buffers for the file name, but the easiest workaround is to use dynamic
allocation.
Fixes: 5e37b9c137ee ("firmware: tegra: Add support for in-band debug")
Link: https://lore.kernel.org/all/20201204193714.3134651-1-arnd@kernel.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
I sent this one in 2020 but got no reply. It still appears to be
required, please have a look.
---
drivers/firmware/tegra/bpmp-debugfs.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/firmware/tegra/bpmp-debugfs.c b/drivers/firmware/tegra/bpmp-debugfs.c
index 3e9fa4b54358..f6888cee83ee 100644
--- a/drivers/firmware/tegra/bpmp-debugfs.c
+++ b/drivers/firmware/tegra/bpmp-debugfs.c
@@ -74,28 +74,34 @@ static void seqbuf_seek(struct seqbuf *seqbuf, ssize_t offset)
static const char *get_filename(struct tegra_bpmp *bpmp,
const struct file *file, char *buf, int size)
{
- char root_path_buf[512];
+ char *root_path_buf;
const char *root_path;
- const char *filename;
+ const char *filename = NULL;
size_t root_len;
+ root_path_buf = kzalloc(512, GFP_KERNEL);
+ if (!root_path_buf)
+ goto out;
+
root_path = dentry_path(bpmp->debugfs_mirror, root_path_buf,
sizeof(root_path_buf));
if (IS_ERR(root_path))
- return NULL;
+ goto out;
root_len = strlen(root_path);
filename = dentry_path(file->f_path.dentry, buf, size);
if (IS_ERR(filename))
- return NULL;
+ goto out;
if (strlen(filename) < root_len ||
strncmp(filename, root_path, root_len))
- return NULL;
+ goto out;
filename += root_len;
+out:
+ kfree(root_path_buf);
return filename;
}
--
2.29.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] [RESEND] firmware: tegra: reduce stack usage 2021-09-27 12:41 [PATCH] [RESEND] firmware: tegra: reduce stack usage Arnd Bergmann @ 2021-10-07 18:11 ` Thierry Reding 2021-10-08 14:43 ` Arnd Bergmann 0 siblings, 1 reply; 3+ messages in thread From: Thierry Reding @ 2021-10-07 18:11 UTC (permalink / raw) To: Arnd Bergmann; +Cc: Jonathan Hunter, Arnd Bergmann, linux-tegra, linux-kernel [-- Attachment #1: Type: text/plain, Size: 2721 bytes --] On Mon, Sep 27, 2021 at 02:41:40PM +0200, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > Building the bpmp-debugfs driver for Arm results in a warning for stack usage: > > drivers/firmware/tegra/bpmp-debugfs.c:321:16: error: stack frame size of 1224 bytes in function 'bpmp_debug_store' [-Werror,-Wframe-larger-than=] > static ssize_t bpmp_debug_store(struct file *file, const char __user *buf, > > It should be possible to rearrange the code to not require two separate > buffers for the file name, but the easiest workaround is to use dynamic > allocation. > > Fixes: 5e37b9c137ee ("firmware: tegra: Add support for in-band debug") > Link: https://lore.kernel.org/all/20201204193714.3134651-1-arnd@kernel.org/ > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > I sent this one in 2020 but got no reply. It still appears to be > required, please have a look. > --- > drivers/firmware/tegra/bpmp-debugfs.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) If this is not a problem on 64-bit ARM, then perhaps we should add that as a dependency. BPMP is only available in Tegra210 and later, all of which are 64-bit. But dynamic allocation also doesn't sound that bad. This is debugfs support, after all, so shouldn't be in any fast path. > > diff --git a/drivers/firmware/tegra/bpmp-debugfs.c b/drivers/firmware/tegra/bpmp-debugfs.c > index 3e9fa4b54358..f6888cee83ee 100644 > --- a/drivers/firmware/tegra/bpmp-debugfs.c > +++ b/drivers/firmware/tegra/bpmp-debugfs.c > @@ -74,28 +74,34 @@ static void seqbuf_seek(struct seqbuf *seqbuf, ssize_t offset) > static const char *get_filename(struct tegra_bpmp *bpmp, > const struct file *file, char *buf, int size) > { > - char root_path_buf[512]; > + char *root_path_buf; > const char *root_path; > - const char *filename; > + const char *filename = NULL; > size_t root_len; > > + root_path_buf = kzalloc(512, GFP_KERNEL); > + if (!root_path_buf) > + goto out; > + > root_path = dentry_path(bpmp->debugfs_mirror, root_path_buf, > sizeof(root_path_buf)); > if (IS_ERR(root_path)) > - return NULL; > + goto out; > > root_len = strlen(root_path); > > filename = dentry_path(file->f_path.dentry, buf, size); > if (IS_ERR(filename)) > - return NULL; > + goto out; Shouldn't this and... > if (strlen(filename) < root_len || > strncmp(filename, root_path, root_len)) > - return NULL; > + goto out; this reset filename to NULL? All callers check for !filename as their error condition. I can fix that up as I apply this, but perhaps shout if you did this on purpose and it needs to stay this way. Thierry [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 833 bytes --] ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] [RESEND] firmware: tegra: reduce stack usage 2021-10-07 18:11 ` Thierry Reding @ 2021-10-08 14:43 ` Arnd Bergmann 0 siblings, 0 replies; 3+ messages in thread From: Arnd Bergmann @ 2021-10-08 14:43 UTC (permalink / raw) To: Thierry Reding Cc: Jonathan Hunter, Arnd Bergmann, open list:TEGRA ARCHITECTURE SUPPORT, Linux Kernel Mailing List On Thu, Oct 7, 2021 at 8:11 PM Thierry Reding <thierry.reding@gmail.com> wrote: > > On Mon, Sep 27, 2021 at 02:41:40PM +0200, Arnd Bergmann wrote: > > From: Arnd Bergmann <arnd@arndb.de> > > > > Building the bpmp-debugfs driver for Arm results in a warning for stack usage: > > > > drivers/firmware/tegra/bpmp-debugfs.c:321:16: error: stack frame size of 1224 bytes in function 'bpmp_debug_store' [-Werror,-Wframe-larger-than=] > > static ssize_t bpmp_debug_store(struct file *file, const char __user *buf, > > > > It should be possible to rearrange the code to not require two separate > > buffers for the file name, but the easiest workaround is to use dynamic > > allocation. > > > > Fixes: 5e37b9c137ee ("firmware: tegra: Add support for in-band debug") > > Link: https://lore.kernel.org/all/20201204193714.3134651-1-arnd@kernel.org/ > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > --- > > I sent this one in 2020 but got no reply. It still appears to be > > required, please have a look. > > --- > > drivers/firmware/tegra/bpmp-debugfs.c | 16 +++++++++++----- > > 1 file changed, 11 insertions(+), 5 deletions(-) > > If this is not a problem on 64-bit ARM, then perhaps we should add that > as a dependency. BPMP is only available in Tegra210 and later, all of > which are 64-bit. > > But dynamic allocation also doesn't sound that bad. This is debugfs > support, after all, so shouldn't be in any fast path. Right, it stays below the warning threshold on 64-bit kernels, but using this much stack is still a bad idea, so fixing it in the driver seems better than hiding it in Kconfig. > > diff --git a/drivers/firmware/tegra/bpmp-debugfs.c b/drivers/firmware/tegra/bpmp-debugfs.c > > index 3e9fa4b54358..f6888cee83ee 100644 > > --- a/drivers/firmware/tegra/bpmp-debugfs.c > > +++ b/drivers/firmware/tegra/bpmp-debugfs.c > > @@ -74,28 +74,34 @@ static void seqbuf_seek(struct seqbuf *seqbuf, ssize_t offset) > > static const char *get_filename(struct tegra_bpmp *bpmp, > > const struct file *file, char *buf, int size) > > { > > - char root_path_buf[512]; > > + char *root_path_buf; > > const char *root_path; > > - const char *filename; > > + const char *filename = NULL; > > size_t root_len; > > > > + root_path_buf = kzalloc(512, GFP_KERNEL); > > + if (!root_path_buf) > > + goto out; > > + > > root_path = dentry_path(bpmp->debugfs_mirror, root_path_buf, > > sizeof(root_path_buf)); > > if (IS_ERR(root_path)) > > - return NULL; > > + goto out; > > > > root_len = strlen(root_path); > > > > filename = dentry_path(file->f_path.dentry, buf, size); > > if (IS_ERR(filename)) > > - return NULL; > > + goto out; > > Shouldn't this and... > > > if (strlen(filename) < root_len || > > strncmp(filename, root_path, root_len)) > > - return NULL; > > + goto out; > > this reset filename to NULL? All callers check for !filename as their > error condition. > > I can fix that up as I apply this, but perhaps shout if you did this on > purpose and it needs to stay this way. Indeed, you are absolutely correct. Thanks for finding the bug and offering to fix it. Arnd ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-10-08 14:43 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-09-27 12:41 [PATCH] [RESEND] firmware: tegra: reduce stack usage Arnd Bergmann 2021-10-07 18:11 ` Thierry Reding 2021-10-08 14:43 ` Arnd Bergmann
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