On Wed, 23 Jul 2025 12:49:25 +0200 Ben Hutchings <b...@debian.org> wrote:
> Currently we add padding between the bootconfig text and footer to > ensure that the footer is aligned within the initramfs image. > However, because only the bootconfig data is held in memory, not the > full initramfs image, the footer may not be naturally aligned in > memory. > > This can result in an alignment fault (SIGBUS) when writing the footer > on some architectures, such as sparc. Aah, got it. > > Build the footer in a struct on the stack before adding it to the > buffer. > > References: > https://buildd.debian.org/status/fetch.php?pkg=linux&arch=sparc64&ver=6.16%7Erc7-1%7Eexp1&stamp=1753209801&raw=0 > Signed-off-by: Ben Hutchings <b...@debian.org> > --- > tools/bootconfig/main.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c > index 4988e23a1422..57c669d2aa90 100644 > --- a/tools/bootconfig/main.c > +++ b/tools/bootconfig/main.c > @@ -11,6 +11,7 @@ > #include <string.h> > #include <errno.h> > #include <endian.h> > +#include <assert.h> > > #include <linux/bootconfig.h> > > @@ -363,7 +364,12 @@ static int delete_xbc(const char *path) > > static int apply_xbc(const char *path, const char *xbc_path) > { > - char *buf, *data, *p; > + struct { > + uint32_t size; > + uint32_t csum; > + char magic[BOOTCONFIG_MAGIC_LEN]; > + } footer; Don't we need __attribute__((__packed__)) for the footer? Thank you, > + char *buf, *data; > size_t total_size; > struct stat stat; > const char *msg; > @@ -433,17 +439,13 @@ static int apply_xbc(const char *path, const char > *xbc_path) > size += pad; > > /* Add a footer */ > - p = data + size; > - *(uint32_t *)p = htole32(size); > - p += sizeof(uint32_t); > + footer.size = htole32(size); > + footer.csum = htole32(csum); > + memcpy(footer.magic, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN); > + static_assert(sizeof(footer) == BOOTCONFIG_FOOTER_SIZE); > + memcpy(data + size, &footer, BOOTCONFIG_FOOTER_SIZE); > > - *(uint32_t *)p = htole32(csum); > - p += sizeof(uint32_t); > - > - memcpy(p, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN); > - p += BOOTCONFIG_MAGIC_LEN; > - > - total_size = p - data; > + total_size = size + BOOTCONFIG_FOOTER_SIZE; > > ret = write(fd, data, total_size); > if (ret < total_size) { -- Masami Hiramatsu (Google) <mhira...@kernel.org>
