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    Subject[PATCH 5.14 333/849] parisc/unwind: fix unwinder when CONFIG_64BIT is enabled
    Date
    From: Sven Schnelle <svens@stackframe.org>

    [ Upstream commit 8e0ba125c2bf1030af3267058019ba86da96863f ]

    With 64 bit kernels unwind_special() is not working because
    it compares the pc to the address of the function descriptor.
    Add a helper function that compares pc with the dereferenced
    address. This fixes all of the backtraces on my c8000. Without
    this changes, a lot of backtraces are missing in kdb or the
    show-all-tasks command from /proc/sysrq-trigger.

    Signed-off-by: Sven Schnelle <svens@stackframe.org>
    Signed-off-by: Helge Deller <deller@gmx.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/parisc/kernel/unwind.c | 21 ++++++++++++++-------
    1 file changed, 14 insertions(+), 7 deletions(-)

    diff --git a/arch/parisc/kernel/unwind.c b/arch/parisc/kernel/unwind.c
    index 87ae476d1c4f5..86a57fb0e6fae 100644
    --- a/arch/parisc/kernel/unwind.c
    +++ b/arch/parisc/kernel/unwind.c
    @@ -21,6 +21,8 @@
    #include <asm/ptrace.h>

    #include <asm/unwind.h>
    +#include <asm/switch_to.h>
    +#include <asm/sections.h>

    /* #define DEBUG 1 */
    #ifdef DEBUG
    @@ -203,6 +205,11 @@ int __init unwind_init(void)
    return 0;
    }

    +static bool pc_is_kernel_fn(unsigned long pc, void *fn)
    +{
    + return (unsigned long)dereference_kernel_function_descriptor(fn) == pc;
    +}
    +
    static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int frame_size)
    {
    /*
    @@ -221,7 +228,7 @@ static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int
    extern void * const _call_on_stack;
    #endif /* CONFIG_IRQSTACKS */

    - if (pc == (unsigned long) &handle_interruption) {
    + if (pc_is_kernel_fn(pc, handle_interruption)) {
    struct pt_regs *regs = (struct pt_regs *)(info->sp - frame_size - PT_SZ_ALGN);
    dbg("Unwinding through handle_interruption()\n");
    info->prev_sp = regs->gr[30];
    @@ -229,13 +236,13 @@ static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int
    return 1;
    }

    - if (pc == (unsigned long) &ret_from_kernel_thread ||
    - pc == (unsigned long) &syscall_exit) {
    + if (pc_is_kernel_fn(pc, ret_from_kernel_thread) ||
    + pc_is_kernel_fn(pc, syscall_exit)) {
    info->prev_sp = info->prev_ip = 0;
    return 1;
    }

    - if (pc == (unsigned long) &intr_return) {
    + if (pc_is_kernel_fn(pc, intr_return)) {
    struct pt_regs *regs;

    dbg("Found intr_return()\n");
    @@ -246,20 +253,20 @@ static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int
    return 1;
    }

    - if (pc == (unsigned long) &_switch_to_ret) {
    + if (pc_is_kernel_fn(pc, _switch_to) ||
    + pc_is_kernel_fn(pc, _switch_to_ret)) {
    info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
    info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
    return 1;
    }

    #ifdef CONFIG_IRQSTACKS
    - if (pc == (unsigned long) &_call_on_stack) {
    + if (pc_is_kernel_fn(pc, _call_on_stack)) {
    info->prev_sp = *(unsigned long *)(info->sp - FRAME_SIZE - REG_SZ);
    info->prev_ip = *(unsigned long *)(info->sp - FRAME_SIZE - RP_OFFSET);
    return 1;
    }
    #endif
    -
    return 0;
    }

    --
    2.33.0


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