[Crash-utility] Re: [PATCH] x86_64: Make ORC_REG_SP and ORC_REG_PREV_SP independent from kernel version

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.

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&gt; --- x86_64.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/x86_64.c b/x86_64.c index 55648697baf3..10e06b942d53 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"); @@ -6736,14 +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") && + 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 info");