Some PT_LOAD segments may be completely zeroed out and their p_filesize
is zero, in that case the loader should just allocate a page that's at
least p_memsz bytes large (plus eventual alignment padding).
Calling zero_bss does this job for us, all we have to do is make sure we
don't try to mmap a zero-length page.
Signed-off-by: Giuseppe Musacchio <thatlemon@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
linux-user/elfload.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index c1a2602..138735b 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2366,11 +2366,19 @@ static void load_elf_image(const char *image_name, int image_fd,
vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_filesz + vaddr_po);
- error = target_mmap(vaddr_ps, vaddr_len,
- elf_prot, MAP_PRIVATE | MAP_FIXED,
- image_fd, eppnt->p_offset - vaddr_po);
- if (error == -1) {
- goto exit_perror;
+ /*
+ * Some segments may be completely empty without any backing file
+ * segment, in that case just let zero_bss allocate an empty buffer
+ * for it.
+ */
+ if (eppnt->p_filesz != 0) {
+ error = target_mmap(vaddr_ps, vaddr_len, elf_prot,
+ MAP_PRIVATE | MAP_FIXED,
+ image_fd, eppnt->p_offset - vaddr_po);
+
+ if (error == -1) {
+ goto exit_perror;
+ }
}
vaddr_ef = vaddr + eppnt->p_filesz;
--
2.20.1
On 03/05/2019 14:20, Giuseppe Musacchio wrote:
> Some PT_LOAD segments may be completely zeroed out and their p_filesize
> is zero, in that case the loader should just allocate a page that's at
> least p_memsz bytes large (plus eventual alignment padding).
>
> Calling zero_bss does this job for us, all we have to do is make sure we
> don't try to mmap a zero-length page.
>
> Signed-off-by: Giuseppe Musacchio <thatlemon@gmail.com>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> linux-user/elfload.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index c1a2602..138735b 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2366,11 +2366,19 @@ static void load_elf_image(const char *image_name, int image_fd,
> vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
> vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_filesz + vaddr_po);
>
> - error = target_mmap(vaddr_ps, vaddr_len,
> - elf_prot, MAP_PRIVATE | MAP_FIXED,
> - image_fd, eppnt->p_offset - vaddr_po);
> - if (error == -1) {
> - goto exit_perror;
> + /*
> + * Some segments may be completely empty without any backing file
> + * segment, in that case just let zero_bss allocate an empty buffer
> + * for it.
> + */
> + if (eppnt->p_filesz != 0) {
> + error = target_mmap(vaddr_ps, vaddr_len, elf_prot,
> + MAP_PRIVATE | MAP_FIXED,
> + image_fd, eppnt->p_offset - vaddr_po);
> +
> + if (error == -1) {
> + goto exit_perror;
> + }
> }
>
> vaddr_ef = vaddr + eppnt->p_filesz;
>
Applied to my linux-user branch.
Thanks,
Laurent
On 03/05/2019 14:20, Giuseppe Musacchio wrote:
> Some PT_LOAD segments may be completely zeroed out and their p_filesize
> is zero, in that case the loader should just allocate a page that's at
> least p_memsz bytes large (plus eventual alignment padding).
>
> Calling zero_bss does this job for us, all we have to do is make sure we
> don't try to mmap a zero-length page.
>
> Signed-off-by: Giuseppe Musacchio <thatlemon@gmail.com>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
I don't find the mail from Peter with his R-b.
Did I miss it?
Thanks,
Laurent
> ---
> linux-user/elfload.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index c1a2602..138735b 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2366,11 +2366,19 @@ static void load_elf_image(const char *image_name, int image_fd,
> vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
> vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_filesz + vaddr_po);
>
> - error = target_mmap(vaddr_ps, vaddr_len,
> - elf_prot, MAP_PRIVATE | MAP_FIXED,
> - image_fd, eppnt->p_offset - vaddr_po);
> - if (error == -1) {
> - goto exit_perror;
> + /*
> + * Some segments may be completely empty without any backing file
> + * segment, in that case just let zero_bss allocate an empty buffer
> + * for it.
> + */
> + if (eppnt->p_filesz != 0) {
> + error = target_mmap(vaddr_ps, vaddr_len, elf_prot,
> + MAP_PRIVATE | MAP_FIXED,
> + image_fd, eppnt->p_offset - vaddr_po);
> +
> + if (error == -1) {
> + goto exit_perror;
> + }
> }
>
> vaddr_ef = vaddr + eppnt->p_filesz;
>
On Thu, 9 May 2019 at 16:50, Laurent Vivier <laurent@vivier.eu> wrote: > > On 03/05/2019 14:20, Giuseppe Musacchio wrote: > > Some PT_LOAD segments may be completely zeroed out and their p_filesize > > is zero, in that case the loader should just allocate a page that's at > > least p_memsz bytes large (plus eventual alignment padding). > > > > Calling zero_bss does this job for us, all we have to do is make sure we > > don't try to mmap a zero-length page. > > > > Signed-off-by: Giuseppe Musacchio <thatlemon@gmail.com> > > Reviewed-by: Peter Maydell <peter.maydell@linaro.org> > > I don't find the mail from Peter with his R-b. > Did I miss it? Patchew has it: https://patchew.org/QEMU/20190418153631.rl3lgadzrqqof72p@debian/ thanks -- PMM
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