Re: [PATCH] [RESEND] firmware: tegra: reduce stack usage
From: Thierry Reding <hidden>
Date: 2021-10-07 18:11:10
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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/ (local)
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.
quoted hunk ↗ jump to hunk
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
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