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efivars: modernize efi_get_variable() a bit

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Primarily, make sure the return parameters are all individually
optional.
This commit is contained in:
Lennart Poettering 2019-07-19 18:29:53 +02:00
parent b19fa8126d
commit c242a08279
1 changed files with 44 additions and 27 deletions
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71
src/shared/efivars.c
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@ -207,25 +207,32 @@ char* efi_variable_path(sd_id128_t vendor, const char *name) {
int efi_get_variable(
sd_id128_t vendor,
const char *name,
uint32_t *attribute,
void **value,
size_t *size) {
uint32_t *ret_attribute,
void **ret_value,
size_t *ret_size) {
_cleanup_close_ int fd = -1;
_cleanup_free_ char *p = NULL;
_cleanup_free_ void *buf = NULL;
struct stat st;
uint32_t a;
ssize_t n;
struct stat st;
_cleanup_free_ void *buf = NULL;
assert(name);
assert(value);
assert(size);
p = efi_variable_path(vendor, name);
if (!p)
return -ENOMEM;
if (!ret_value && !ret_size && !ret_attribute) {
/* If caller is not interested in anything, just check if the variable exists and is readable
* to us. */
if (access(p, R_OK) < 0)
return -errno;
return 0;
}
fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC);
if (fd < 0)
return -errno;
@ -237,31 +244,41 @@ int efi_get_variable(
if (st.st_size > 4*1024*1024 + 4)
return -E2BIG;
n = read(fd, &a, sizeof(a));
if (n < 0)
return -errno;
if (n != sizeof(a))
return -EIO;
if (ret_value || ret_attribute) {
n = read(fd, &a, sizeof(a));
if (n < 0)
return -errno;
if (n != sizeof(a))
return -EIO;
}
buf = malloc(st.st_size - 4 + 2);
if (!buf)
return -ENOMEM;
if (ret_value) {
buf = malloc(st.st_size - 4 + 2);
if (!buf)
return -ENOMEM;
n = read(fd, buf, (size_t) st.st_size - 4);
if (n < 0)
return -errno;
if (n != (ssize_t) st.st_size - 4)
return -EIO;
n = read(fd, buf, (size_t) st.st_size - 4);
if (n < 0)
return -errno;
if (n != st.st_size - 4)
return -EIO;
/* Always NUL terminate (2 bytes, to protect UTF-16) */
((char*) buf)[st.st_size - 4] = 0;
((char*) buf)[st.st_size - 4 + 1] = 0;
/* Always NUL terminate (2 bytes, to protect UTF-16) */
((char*) buf)[st.st_size - 4] = 0;
((char*) buf)[st.st_size - 4 + 1] = 0;
}
*value = TAKE_PTR(buf);
*size = (size_t) st.st_size - 4;
/* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable
* with a smaller value. */
if (attribute)
*attribute = a;
if (ret_attribute)
*ret_attribute = a;
if (ret_value)
*ret_value = TAKE_PTR(buf);
if (ret_size)
*ret_size = (size_t) st.st_size - 4;
return 0;
}