# \[PATCH RFC 06/22\] powerpc/rtas: let procfs copy out reads - From: Christian Brauner \ - Date: 2026-11-02 15:03:32 - List: linuxppc-dev - Page: https://ratatoskr.run/linuxppc-dev/2026/11/17845353 - Thread: https://ratatoskr.run/linux-fsdevel/2026/11/17844895/t.md ```text Implement ->proc_read_buf() for the error log and the flash files so procfs copies what is read to userspace after it unpinned the entry. The error log hands out a record the way it did before, the record is consumed before it reaches userspace. A reader that passes a NULL buffer now loses a record like one that passed a bad buffer always did, instead of getting -EINVAL. The files can be spliced now, like every entry that is read through ->read_iter(). Note that a sendfile() from the error log into a target that fails or takes less than was read drops the records in between, splice_direct_to_actor() rewinds any seekable file like that and the error log doesn't hand a record out twice. Signed-off-by: Christian Brauner (Amutable) --- arch/powerpc/kernel/rtas_flash.c | 24 ++++++++++++------------ arch/powerpc/kernel/rtasd.c | 19 +++++-------------- 2 files changed, 17 insertions(+), 26 deletions(-) diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c index 77a4627f2507..5ebaee7683ef 100644 --- a/arch/powerpc/kernel/rtas_flash.c +++ b/arch/powerpc/kernel/rtas_flash.c @@ -269,7 +269,7 @@ static size_t get_flash_status_msg(int status, char *buf) } /* Reading the proc file will show status (not the firmware contents) */ -static ssize_t rtas_flash_read_msg(struct file *file, char __user *buf, +static ssize_t rtas_flash_read_msg(struct file *file, char *buf, size_t count, loff_t *ppos) { struct rtas_update_flash_t *const uf = &rtas_update_flash_data; @@ -283,10 +283,10 @@ static ssize_t rtas_flash_read_msg(struct file *file, char __user *buf, /* Read as text message */ len = get_flash_status_msg(status, msg); - return simple_read_from_buffer(buf, count, ppos, msg, len); + return memory_read_from_buffer(buf, count, ppos, msg, len); } -static ssize_t rtas_flash_read_num(struct file *file, char __user *buf, +static ssize_t rtas_flash_read_num(struct file *file, char *buf, size_t count, loff_t *ppos) { struct rtas_update_flash_t *const uf = &rtas_update_flash_data; @@ -299,7 +299,7 @@ static ssize_t rtas_flash_read_num(struct file *file, char __user *buf, /* Read as number */ sprintf(msg, "%d\n", status); - return simple_read_from_buffer(buf, count, ppos, msg, strlen(msg)); + return memory_read_from_buffer(buf, count, ppos, msg, strlen(msg)); } /* We could be much more efficient here. But to keep this function @@ -370,7 +370,7 @@ static void manage_flash(struct rtas_manage_flash_t *args_buf, unsigned int op) args_buf->status = rc; } -static ssize_t manage_flash_read(struct file *file, char __user *buf, +static ssize_t manage_flash_read(struct file *file, char *buf, size_t count, loff_t *ppos) { struct rtas_manage_flash_t *const args_buf = &rtas_manage_flash_data; @@ -382,7 +382,7 @@ static ssize_t manage_flash_read(struct file *file, char __user *buf, mutex_unlock(&rtas_manage_flash_mutex); msglen = sprintf(msg, "%d\n", status); - return simple_read_from_buffer(buf, count, ppos, msg, msglen); + return memory_read_from_buffer(buf, count, ppos, msg, msglen); } static ssize_t manage_flash_write(struct file *file, char *buf, @@ -450,7 +450,7 @@ static int get_validate_flash_msg(struct rtas_validate_flash_t *args_buf, return n; } -static ssize_t validate_flash_read(struct file *file, char __user *buf, +static ssize_t validate_flash_read(struct file *file, char *buf, size_t count, loff_t *ppos) { struct rtas_validate_flash_t *const args_buf = @@ -462,7 +462,7 @@ static ssize_t validate_flash_read(struct file *file, char __user *buf, msglen = get_validate_flash_msg(args_buf, msg, VALIDATE_MSG_LEN); mutex_unlock(&rtas_validate_flash_mutex); - return simple_read_from_buffer(buf, count, ppos, msg, msglen); + return memory_read_from_buffer(buf, count, ppos, msg, msglen); } static ssize_t validate_flash_write(struct file *file, char *buf, @@ -623,7 +623,7 @@ static const struct rtas_flash_file rtas_flash_files[] = { .handle = RTAS_FN_IBM_UPDATE_FLASH_64_AND_REBOOT, .status = &rtas_update_flash_data.status, .ops.proc_flags = PROC_ENTRY_SHORT_WRITES, - .ops.proc_read = rtas_flash_read_msg, + .ops.proc_read_buf = rtas_flash_read_msg, .ops.proc_write_buf = rtas_flash_write, .ops.proc_write_size = RTAS_BLK_SIZE, .ops.proc_release = rtas_flash_release, @@ -634,7 +634,7 @@ static const struct rtas_flash_file rtas_flash_files[] = { .handle = RTAS_FN_IBM_UPDATE_FLASH_64_AND_REBOOT, .status = &rtas_update_flash_data.status, .ops.proc_flags = PROC_ENTRY_SHORT_WRITES, - .ops.proc_read = rtas_flash_read_num, + .ops.proc_read_buf = rtas_flash_read_num, .ops.proc_write_buf = rtas_flash_write, .ops.proc_write_size = RTAS_BLK_SIZE, .ops.proc_release = rtas_flash_release, @@ -645,7 +645,7 @@ static const struct rtas_flash_file rtas_flash_files[] = { .handle = RTAS_FN_IBM_VALIDATE_FLASH_IMAGE, .status = &rtas_validate_flash_data.status, .ops.proc_flags = PROC_ENTRY_SHORT_WRITES, - .ops.proc_read = validate_flash_read, + .ops.proc_read_buf = validate_flash_read, .ops.proc_write_buf = validate_flash_write, .ops.proc_write_size = VALIDATE_BUF_SIZE, .ops.proc_release = validate_flash_release, @@ -655,7 +655,7 @@ static const struct rtas_flash_file rtas_flash_files[] = { .filename = "powerpc/rtas/" MANAGE_FLASH_NAME, .handle = RTAS_FN_IBM_MANAGE_FLASH_IMAGE, .status = &rtas_manage_flash_data.status, - .ops.proc_read = manage_flash_read, + .ops.proc_read_buf = manage_flash_read, .ops.proc_write_buf = manage_flash_write, .ops.proc_lseek = default_llseek, } diff --git a/arch/powerpc/kernel/rtasd.c b/arch/powerpc/kernel/rtasd.c index dd0df5e164a3..360ed2e30fd5 100644 --- a/arch/powerpc/kernel/rtasd.c +++ b/arch/powerpc/kernel/rtasd.c @@ -291,26 +291,18 @@ static int rtas_log_release(struct inode * inode, struct file * file) * know that we can safely clear the events in NVRAM. * Next we'll sit and wait for something else to log. */ -static ssize_t rtas_log_read(struct file * file, char __user * buf, +static ssize_t rtas_log_read(struct file * file, char * buf, size_t count, loff_t *ppos) { int error; - char *tmp; unsigned long s; unsigned long offset; - if (!buf || count < rtas_error_log_buffer_max) + if (count < rtas_error_log_buffer_max) return -EINVAL; count = rtas_error_log_buffer_max; - if (!access_ok(buf, count)) - return -EFAULT; - - tmp = kmalloc(count, GFP_KERNEL); - if (!tmp) - return -ENOMEM; - spin_lock_irqsave(&rtasd_log_lock, s); /* if it's 0, then we know we got the last one (the one in NVRAM) */ @@ -338,15 +330,14 @@ static ssize_t rtas_log_read(struct file * file, char __user * buf, } offset = rtas_error_log_buffer_max * (rtas_log_start & LOG_NUMBER_MASK); - memcpy(tmp, &rtas_log_buf[offset], count); + memcpy(buf, &rtas_log_buf[offset], count); rtas_log_start += 1; rtas_log_size -= 1; spin_unlock_irqrestore(&rtasd_log_lock, s); - error = copy_to_user(buf, tmp, count) ? -EFAULT : count; + error = count; out: - kfree(tmp); return error; } @@ -359,7 +350,7 @@ static __poll_t rtas_log_poll(struct file *file, poll_table * wait) } static const struct proc_ops rtas_log_proc_ops = { - .proc_read = rtas_log_read, + .proc_read_buf = rtas_log_read, .proc_poll = rtas_log_poll, .proc_open = rtas_log_open, .proc_release = rtas_log_release, -- 2.53.0 ```