Re: [PATCH v3 12/12] kdump: Use vmlinux_build_id to simplify

Baoquan He
2021-04-08T10:17:57Z

On 04/07/21 at 07:03pm, Petr Mladek wrote:
> On Tue 2021-03-30 20:05:20, Stephen Boyd wrote:
> > We can use the vmlinux_build_id array here now instead of open coding
> > it. This mostly consolidates code.
> >
> > Cc: Jiri Olsa <jolsa@kernel.org>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Jessica Yu <jeyu@kernel.org>
> > Cc: Evan Green <evgreen@chromium.org>
> > Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: Vivek Goyal <vgoyal@redhat.com>
> > Cc: <kexec@lists.infradead.org>
> > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > ---
> > include/linux/crash_core.h | 6 +-----
> > kernel/crash_core.c | 41 ++------------------------------------
> > 2 files changed, 3 insertions(+), 44 deletions(-)
> >
> > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> > index 206bde8308b2..fb8ab99bb2ee 100644
> > --- a/include/linux/crash_core.h
> > +++ b/include/linux/crash_core.h
> > @@ -39,7 +39,7 @@ phys_addr_t paddr_vmcoreinfo_note(void);
> > #define VMCOREINFO_OSRELEASE(value) \
> > vmcoreinfo_append_str("OSRELEASE=%s\n", value)
> > #define VMCOREINFO_BUILD_ID(value) \
> > - vmcoreinfo_append_str("BUILD-ID=%s\n", value)
> > + vmcoreinfo_append_str("BUILD-ID=%20phN\n", value)

I may miss something, wondering why we need add '20' here.

>
> Please, add also build check that BUILD_ID_MAX == 20.
>
>
> > #define VMCOREINFO_PAGESIZE(value) \
> > vmcoreinfo_append_str("PAGESIZE=%ld\n", value)
> > #define VMCOREINFO_SYMBOL(name) \
> > @@ -69,10 +69,6 @@ extern unsigned char *vmcoreinfo_data;
> > extern size_t vmcoreinfo_size;
> > extern u32 *vmcoreinfo_note;
> >
> > -/* raw contents of kernel .notes section */
> > -extern const void __start_notes __weak;
> > -extern const void __stop_notes __weak;
> > -
> > Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
> > void *data, size_t data_len);
> > void final_note(Elf_Word *buf);
> > diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> > index 825284baaf46..6b560cf9f374 100644
> > --- a/kernel/crash_core.c
> > +++ b/kernel/crash_core.c
> > @@ -4,6 +4,7 @@
> > * Copyright (C) 2002-2004 Eric Biederman <ebiederm@xmission.com>
> > */
> >
> > +#include <linux/buildid.h>
> > #include <linux/crash_core.h>
> > #include <linux/utsname.h>
> > #include <linux/vmalloc.h>
> > @@ -378,51 +379,13 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
> > }
> > EXPORT_SYMBOL(paddr_vmcoreinfo_note);
> >
> > -#define NOTES_SIZE (&__stop_notes - &__start_notes)
> > -#define BUILD_ID_MAX SHA1_DIGEST_SIZE
> > -#define NT_GNU_BUILD_ID 3
> > -
> > -struct elf_note_section {
> > - struct elf_note n_hdr;
> > - u8 n_data[];
> > -};
> > -
> > /*
> > * Add build ID from .notes section as generated by the GNU ld(1)
> > * or LLVM lld(1) --build-id option.
> > */
> > static void add_build_id_vmcoreinfo(void)
> > {
> > - char build_id[BUILD_ID_MAX * 2 + 1];
> > - int n_remain = NOTES_SIZE;
> > -
> > - while (n_remain >= sizeof(struct elf_note)) {
> > - const struct elf_note_section *note_sec =
> > - &__start_notes + NOTES_SIZE - n_remain;
> > - const u32 n_namesz = note_sec->n_hdr.n_namesz;
> > -
> > - if (note_sec->n_hdr.n_type == NT_GNU_BUILD_ID &&
> > - n_namesz != 0 &&
> > - !strcmp((char *)&note_sec->n_data[0], "GNU")) {
> > - if (note_sec->n_hdr.n_descsz <= BUILD_ID_MAX) {
> > - const u32 n_descsz = note_sec->n_hdr.n_descsz;
> > - const u8 *s = &note_sec->n_data[n_namesz];
> > -
> > - s = PTR_ALIGN(s, 4);
> > - bin2hex(build_id, s, n_descsz);
> > - build_id[2 * n_descsz] = '\0';
> > - VMCOREINFO_BUILD_ID(build_id);
> > - return;
> > - }
> > - pr_warn("Build ID is too large to include in vmcoreinfo: %u > %u\n",
> > - note_sec->n_hdr.n_descsz,
> > - BUILD_ID_MAX);
> > - return;
> > - }
> > - n_remain -= sizeof(struct elf_note) +
> > - ALIGN(note_sec->n_hdr.n_namesz, 4) +
> > - ALIGN(note_sec->n_hdr.n_descsz, 4);
> > - }
> > + VMCOREINFO_BUILD_ID(vmlinux_build_id);
> > }
>
> The function add_build_id_vmcoreinfo() is used in
> crash_save_vmcoreinfo_init() in this context:
>
>
> VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
> add_build_id_vmcoreinfo();
> VMCOREINFO_PAGESIZE(PAGE_SIZE);
>
> VMCOREINFO_SYMBOL(init_uts_ns);
> VMCOREINFO_OFFSET(uts_namespace, name);
> VMCOREINFO_SYMBOL(node_online_map);
>
> The function is not longer need. VMCOREINFO_BUILD_ID()
> can be used directly:
>
> VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
> VMCOREINFO_BUILD_ID(vmlinux_build_id);
> VMCOREINFO_PAGESIZE(PAGE_SIZE);
>
> VMCOREINFO_SYMBOL(init_uts_ns);
> VMCOREINFO_OFFSET(uts_namespace, name);
> VMCOREINFO_SYMBOL(node_online_map);
>
>
> Best Regards,
> Petr
>
>
> >
> > static int __init crash_save_vmcoreinfo_init(void)
> > --
> > https://chromeos.dev
>