Hi Mikhail,
> -----Original Message-----
> Hello Kazu,
>
> I think we can try to generalize the kaslr offset extraction.
> I won't speak for other architectures, but for s390 that
> get_kaslr_offset_arm64()
> should work fine. The only concern of mine is this TODO statement:
>
> if (_text <= vaddr && vaddr <= _end) {
> DEBUG_MSG("info->kaslr_offset: %lx\n", info->kaslr_offset);
> return info->kaslr_offset;
> } else {
> /*
> * TODO: we need to check if it is vmalloc/vmmemmap/module
> * address, we will have different offset
> */
> return 0;
> }
>
> Could you explain this one?
Probably it was considered that the check would be needed to support
the whole KASLR behavior when get_kaslr_offset_x86_64() was written
originally.
But in the current makedumpfile for x86_64 and arm64 supporting KASLR,
the offset we need is the one for symbol addresses in vmlinux only.
As I said below, module symbol addresses are retrieved from vmcore.
Other addresses should not be passed to the function for now, as far
as I know.
So I think the TODO comment is confusing, and it would be better to
remove it or change it to something like:
/*
* Returns 0 if vaddr does not need the offset to be added,
* e.g. for module address.
*/
But if s390 uses get_kaslr_offset() in its arch-specific code to
adjust addresses other than kernel text address, we might need to
modify it for s390, not generalize it.
Thanks,
Kazu
>
> Thanks,
> Mikhail
>
> On 09.12.2019 23:02, Kazuhito Hagio wrote:
> > Hi Mikhail,
> >
> > Sorry for late reply.
> >
> >> -----Original Message-----
> >> Since kernel v5.2 KASLR is supported on s390. In makedumpfile however no
> >> support has been added yet. This patch adds the arch specific function
> >> get_kaslr_offset() for s390x.
> >> Since the values in vmcoreinfo are already relocated, the patch is
> >> mainly relevant for vmlinux processing (-x option).
> >
> > In the current implementation of makedumpfile, the get_kaslr_offset(vaddr)
> > is supposed to return the KASLR offset only when the offset is needed to
> > add to the vaddr. So generally symbols from kernel (vmlinux) need it, but
> > symbols from modules are resolved dynamically and don't need the offset.
> \>
> > This patch always returns the offset if any, as a result, I guess this patch
> > will not work as expected with module symbols in filter config file.
> >
> > So... How about making get_kaslr_offset_arm64() general for other archs
> > (get_kaslr_offset_general() or something), then using it also for s390?
> > If OK, I can do that generalization.
> >
> > Thanks,
> > Kazu
> >
> >>
> >> Signed-off-by: Philipp Rudo <pr...@linux.ibm.com>
> >> Signed-off-by: Mikhail Zaslonko <zaslo...@linux.ibm.com>
> >> ---
> >> arch/s390x.c | 32 ++++++++++++++++++++++++++++++++
> >> makedumpfile.h | 3 ++-
> >> 2 files changed, 34 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/s390x.c b/arch/s390x.c
> >> index bf9d58e..892df14 100644
> >> --- a/arch/s390x.c
> >> +++ b/arch/s390x.c
> >> @@ -122,6 +122,38 @@ get_machdep_info_s390x(void)
> >> return TRUE;
> >> }
> >>
> >> +unsigned long
> >> +get_kaslr_offset_s390x(unsigned long vaddr)
> >> +{
> >> + unsigned int i;
> >> + char buf[BUFSIZE_FGETS], *endp;
> >> +
> >> + if (!info->file_vmcoreinfo)
> >> + return FALSE;
> >> +
> >> + if (fseek(info->file_vmcoreinfo, 0, SEEK_SET) < 0) {
> >> + ERRMSG("Can't seek the vmcoreinfo file(%s). %s\n",
> >> + info->name_vmcoreinfo, strerror(errno));
> >> + return FALSE;
> >> + }
> >> +
> >> + while (fgets(buf, BUFSIZE_FGETS, info->file_vmcoreinfo)) {
> >> + i = strlen(buf);
> >> + if (!i)
> >> + break;
> >> + if (buf[i - 1] == '\n')
> >> + buf[i - 1] = '\0';
> >> + if (strncmp(buf, STR_KERNELOFFSET,
> >> + strlen(STR_KERNELOFFSET)) == 0) {
> >> + info->kaslr_offset =
> >> + strtoul(buf + strlen(STR_KERNELOFFSET), &endp,
> >> 16);
> >> + DEBUG_MSG("info->kaslr_offset: %lx\n",
> >> info->kaslr_offset);
> >> + }
> >> + }
> >> +
> >> + return info->kaslr_offset;
> >> +}
> >> +
> >> static int
> >> is_vmalloc_addr_s390x(unsigned long vaddr)
> >> {
> >> diff --git a/makedumpfile.h b/makedumpfile.h
> >> index ac11e90..26f6247 100644
> >> --- a/makedumpfile.h
> >> +++ b/makedumpfile.h
> >> @@ -1071,11 +1071,12 @@ unsigned long long vaddr_to_paddr_ppc(unsigned
> >> long vaddr);
> >> int get_machdep_info_s390x(void);
> >> unsigned long long vaddr_to_paddr_s390x(unsigned long vaddr);
> >> int is_iomem_phys_addr_s390x(unsigned long addr);
> >> +unsigned long get_kaslr_offset_s390x(unsigned long vaddr);
> >> #define find_vmemmap() stub_false()
> >> #define get_phys_base() stub_true()
> >> #define get_machdep_info() get_machdep_info_s390x()
> >> #define get_versiondep_info() stub_true()
> >> -#define get_kaslr_offset(X) stub_false()
> >> +#define get_kaslr_offset(X) get_kaslr_offset_s390x(X)
> >> #define vaddr_to_paddr(X) vaddr_to_paddr_s390x(X)
> >> #define paddr_to_vaddr(X) paddr_to_vaddr_general(X)
> >> #define is_phys_addr(X) is_iomem_phys_addr_s390x(X)
> >> --
> >> 2.17.1
> >>
> >
> >
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