[Crash-utility] Re: [PATCH v2] x86_64: Make ORC_REG_SP and ORC_REG_PREV_SP independent from kernel version
On 2026/08/04 15:57, Tao Liu wrote:
Previously ORC_REG_SP and ORC_REG_PREV_SP will depend on kernel
version
for their value, however this is fragile since distributions will
backport the upstream patch to a lower kernel version, thus break the
version assumption.
This patch fixes by checking the value of ORC_REG_PREV_SP, which can be
get from orc_fp_entry. ORC_REG_PREV_SP's value can work as the indicator
of whether the current kernel have applied the upstream patch 1735858caa4b
("objtool/x86: Reorder ORC register numbering").
Fixes: d0ee428664f9 ("x86_64: Fix "bt" command to use correct ORC
register
values on Linux 7.1 and later")
Signed-off-by: Tao Liu <ltao(a)redhat.com>
thank you for the fix, looks good to me.
Thanks,
Kazu
> ---
> v2 -> v1: emit error(WARN) for kernels which doesn't have orc_fp_entry
> symbol.
> ---
> x86_64.c | 30 +++++++++++++++++++++++-------
> 1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/x86_64.c b/x86_64.c
> index 55648697baf3..81d20ed419d5 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -6661,6 +6661,9 @@ x86_64_ORC_init(void)
> NULL
> };
> struct ORC_data *orc;
> + struct gnu_request request, *req;
> + req = &request;
> + ulong value = 0;
>
> MEMBER_OFFSET_INIT(inactive_task_frame_bp, "inactive_task_frame",
"bp");
> MEMBER_OFFSET_INIT(inactive_task_frame_ret_addr, "inactive_task_frame",
"ret_addr");
> @@ -6736,13 +6739,26 @@ x86_64_ORC_init(void)
> if (orc->has_signal && !orc->has_end)
> machdep->flags |= ORC_6_4;
>
> - /* See kernel commit 1735858caa4b */
> - if (THIS_KERNEL_VERSION >= LINUX(7,1,0)) {
> - ORC_REG_SP = 3;
> - ORC_REG_PREV_SP = 8;
> - } else {
> - ORC_REG_SP = 5;
> - ORC_REG_PREV_SP = 1;
> + /* Try get ORC_REG_(PREV)_SP */
> + ORC_REG_SP = 5;
> + ORC_REG_PREV_SP = 1;
> +
> + if (kernel_symbol_exists("orc_fp_entry")) {
> + if (get_symbol_type("orc_fp_entry", "bp_reg", req) ==
TYPE_CODE_INT) {
> + get_symbol_data("orc_fp_entry", sizeof(ulong), &value);
> + /*
> + * orc_fp_entry.bp_reg = ORC_REG_PREV_SP
> + * See kernel commit 1735858caa4b. Use ORC_REG_PREV_SP as the
> + * indicator of the commit.
> + */
> + value >>= req->member_offset;
> + value &= ((1UL << req->member_length) - 1);
> + if (value == 8) {
> + ORC_REG_SP = 3;
> + ORC_REG_PREV_SP = 8;
> + }
> + } else
> + error(WARNING, "Cannot get orc_fp_entry.bp_reg info");
> }
>
> machdep->flags |= ORC;