> Date: Thu, 9 Dec 2021 01:05:07 +0000
> From: "d.hatayama@xxxxxxxxxxx" <d.hatayama@xxxxxxxxxxx>
> To: "crash-utility@xxxxxxxxxx" <crash-utility@xxxxxxxxxx>
> Subject: [PATCH] defs.h: fix breakage of compatibility
> of struct machdep_table for extension modules
> Message-ID:
> <TYAPR01MB6507D1D65B85CCE7567511AF95709@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
>
> Content-Type: text/plain; charset="iso-2022-jp"
>
> Commit 2f967fb5ebd737ce5eadba462df35935122e8865 (crash_taget:
> fetch_registers support) added new member get_cpu_reg in the middle of
> struct machdep_table as:
>
> @@ -1013,6 +1013,7 @@ struct machdep_table {
> ulong (*processor_speed)(void);
> int (*uvtop)(struct task_context *, ulong, physaddr_t *, int);
> int (*kvtop)(struct task_context *, ulong, physaddr_t *, int);
> + int (*get_cpu_reg)(int, int, const char *, int, void *);
> ulong (*get_task_pgd)(ulong);
> void (*dump_irq)(int);
> void (*get_stack_frame)(struct bt_info *, ulong *, ulong *);
>
> which breaks compatibility of struct machdep_table for extension
> modules. In general, new member variables must be added at the end of
> structures to maintain compatibility of data structures shared among
> extension modules.
>
This is similar with another issue, see its reply:
https://listman.redhat.com/archives/crash-utility/2021-December/msg00008.html
> For example, as the result, crash gcore command results in unexpected
> behavior:
>
> crash> gcore -v 7
> GETBUF(168 -> 0)
> <readmem: ffff8b267dd28020, KVADDR, "task_struct.stack", 8, (FOE), 7fffaef8afa8>
> <read_kdump: addr: ffff8b267dd28020 paddr: 7dd28020 cnt: 8>
> read_netdump: addr: ffff8b267dd28020 paddr: 7dd28020 cnt: 8 offset: 767ec020
> <readmem: ffffa3f740abff58, KVADDR, "genregs_get: pt_regs", 168, (FOE), e71f80>
> gcore: invalid kernel virtual address: ffffa3f740abff58 type: "genregs_get: pt_regs"
> vma hit rate: 0% (0 of 274308)
>
> crash gcore uses machdep->get_stacktop() to retrieve registers saved
> at the bottom of a given user-space task's kernel stack:
>
> static int genregs_get(struct task_context *target,
> const struct user_regset *regset,
> unsigned int size, void *buf)
> {
> ...snip...
> pt_regs_buf = GETBUF(SIZE(pt_regs));
>
> readmem(machdep->get_stacktop(target->task) - SIZE(pt_regs), KVADDR,
> pt_regs_buf, SIZE(pt_regs), "genregs_get: pt_regs",
> gcore_verbose_error_handle());
>
> As seen above, the position of get_stacktop in struct machdep_table is
> behind the position where get_cpu_reg was added:
>
> int (*uvtop)(struct task_context *, ulong, physaddr_t *, int);
> int (*kvtop)(struct task_context *, ulong, physaddr_t *, int);
> int (*get_cpu_reg)(int, int, const char *, int, void *); ulong (*get_task_pgd)(ulong);
> void (*dump_irq)(int);
> void (*get_stack_frame)(struct bt_info *, ulong *, ulong *);
> ulong (*get_stackbase)(ulong);
> ulong (*get_stacktop)(ulong);
>
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxx>
> ---
> defs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/defs.h b/defs.h
> index e9e8143..b63741c 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -1013,7 +1013,6 @@ struct machdep_table {
> ulong (*processor_speed)(void);
> int (*uvtop)(struct task_context *, ulong, physaddr_t *, int);
> int (*kvtop)(struct task_context *, ulong, physaddr_t *, int);
> - int (*get_cpu_reg)(int, int, const char *, int, void *);
> ulong (*get_task_pgd)(ulong);
> void (*dump_irq)(int);
> void (*get_stack_frame)(struct bt_info *, ulong *, ulong *);
> @@ -1063,6 +1062,7 @@ struct machdep_table {
> void (*get_irq_affinity)(int);
> void (*show_interrupts)(int, ulong *);
> int (*is_page_ptr)(ulong, physaddr_t *);
> + int (*get_cpu_reg)(int, int, const char *, int, void *);
> };
>
Acked-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> /*
> --
> 2.31.1
--
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