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[linux] Do not assume that stat() works on sysfs files 

Linux kernel 3.12 and earlier report a zero size via stat() for all
ACPI table files in sysfs.  There is no way to determine the file size
other than by reading the file until EOF.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/310/head
Michael Brown 2021-03-03 02:24:32 +00:00
parent 1c4917b6a7
commit 65bd5c05db
1 changed files with 21 additions and 30 deletions
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43
src/interface/linux/linux_sysfs.c
View File

@ -32,6 +32,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
* *
*/ */
/** Read blocksize */
#define LINUX_SYSFS_BLKSIZE 4096
/** /**
* Read file from sysfs * Read file from sysfs
* *
@ -40,9 +43,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
* @ret len Length read, or negative error * @ret len Length read, or negative error
*/ */
int linux_sysfs_read ( const char *filename, userptr_t *data ) { int linux_sysfs_read ( const char *filename, userptr_t *data ) {
size_t offset; userptr_t tmp;
size_t len;
ssize_t read; ssize_t read;
size_t len;
int fd; int fd;
int rc; int rc;
@ -55,37 +58,27 @@ int linux_sysfs_read ( const char *filename, userptr_t *data ) {
goto err_open; goto err_open;
} }
/* Get file length */ /* Read file */
if ( linux_fstat_size ( fd, &len ) == -1 ) { for ( *data = UNULL, len = 0 ; ; len += read ) {
rc = -ELINUX ( linux_errno );
DBGC ( filename, "LINUX could not stat %s: %s\n",
filename, linux_strerror ( linux_errno ) );
goto err_stat;
}
/* Allocate buffer */ /* (Re)allocate space */
*data = umalloc ( len ); tmp = urealloc ( *data, ( len + LINUX_SYSFS_BLKSIZE ) );
if ( ! *data ) { if ( ! tmp ) {
rc = -ENOMEM; rc = -ENOMEM;
DBGC ( filename, "LINUX could not allocate %zd bytes for %s\n",
len, filename );
goto err_alloc; goto err_alloc;
} }
*data = tmp;
/* Read file */ /* Read from file */
for ( offset = 0 ; offset < len ; offset += read ) { read = linux_read ( fd, user_to_virt ( *data, len ),
read = linux_read ( fd, user_to_virt ( *data, offset ), len ); LINUX_SYSFS_BLKSIZE );
if ( read == 0 )
break;
if ( read < 0 ) { if ( read < 0 ) {
DBGC ( filename, "LINUX could not read %s: %s\n", DBGC ( filename, "LINUX could not read %s: %s\n",
filename, linux_strerror ( linux_errno ) ); filename, linux_strerror ( linux_errno ) );
goto err_read; goto err_read;
} }
if ( read == 0 ) {
rc = -EIO;
DBGC ( filename, "LINUX read underlength %s\n",
filename );
goto err_eof;
}
} }
/* Close file */ /* Close file */
@ -94,11 +87,9 @@ int linux_sysfs_read ( const char *filename, userptr_t *data ) {
DBGC ( filename, "LINUX read %s\n", filename ); DBGC ( filename, "LINUX read %s\n", filename );
return len; return len;
err_eof:
err_read: err_read:
ufree ( *data );
err_alloc: err_alloc:
err_stat: ufree ( *data );
linux_close ( fd ); linux_close ( fd );
err_open: err_open:
return rc; return rc;