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&gt; --- v3 -> v2: Remove data type query of orc_fp_entry, just use kernel_orc_entry_6_4 which already contained in crash utility for bp_reg offset resolving. --- x86_64.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/x86_64.c b/x86_64.c index 55648697baf3..d192f3bcdd20 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; + ulong value = 0; + req = &request;

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 +6739,28 @@ 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")) { + /* + * kernel_orc_entry_6_4 & kernel_orc_entry have the same + * offset of bp_reg. + */ + kernel_orc_entry_6_4 entry = {0}; + if (try_get_symbol_data("orc_fp_entry", sizeof(entry), &entry)) { + /* + * orc_fp_entry.bp_reg = ORC_REG_PREV_SP + * See kernel commit 1735858caa4b. Use ORC_REG_PREV_SP + * as the indicator of the commit. + */ + if (entry.bp_reg == 8) { + ORC_REG_SP = 3; + ORC_REG_PREV_SP = 8; + } + } else + error(WARNING, "Cannot get orc_fp_entry.bp_reg info"); } machdep->flags |= ORC;

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&gt; --- v3 -> v2: Remove data type query of orc_fp_entry, just use kernel_orc_entry_6_4 which already contained in crash utility for bp_reg offset resolving. --- x86_64.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/x86_64.c b/x86_64.c index 55648697baf3..d192f3bcdd20 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; + ulong value = 0; + req = &request; 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 +6739,28 @@ 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")) { + /* + * kernel_orc_entry_6_4 & kernel_orc_entry have the same + * offset of bp_reg. + */ + kernel_orc_entry_6_4 entry = {0}; + if (try_get_symbol_data("orc_fp_entry", sizeof(entry), &entry)) { + /* + * orc_fp_entry.bp_reg = ORC_REG_PREV_SP + * See kernel commit 1735858caa4b. Use ORC_REG_PREV_SP + * as the indicator of the commit. + */ + if (entry.bp_reg == 8) { + ORC_REG_SP = 3; + ORC_REG_PREV_SP = 8;

+ } + } else + error(WARNING, "Cannot get orc_fp_entry.bp_reg info"); } machdep->flags |= ORC;

Hi Tao, On 8/6/26 8:16 AM, 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&gt; > --- > v3 -> v2: Remove data type query of orc_fp_entry, just use kernel_orc_entry_6_4 > which already contained in crash utility for bp_reg offset resolving. > --- > x86_64.c | 32 +++++++++++++++++++++++++------- > 1 file changed, 25 insertions(+), 7 deletions(-) > > diff --git a/x86_64.c b/x86_64.c > index 55648697baf3..d192f3bcdd20 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; > + ulong value = 0; > + req = &request; > > 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 +6739,28 @@ 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; How about use the newere values as default, and check the symbol data and set them as old ones if needed?

Hi Dave, On Sun, Aug 9, 2026 at 1:54 PM Dave Young <yangrr.2009(a)tsinghua.org.cn&gt; wrote: > > > > On 8/8/26 8:11 PM, Dave Young wrote: > > Hi Tao, > > > > On 8/6/26 8:16 AM, 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&gt; > >> --- > >> v3 -> v2: Remove data type query of orc_fp_entry, just use kernel_orc_entry_6_4 > >> which already contained in crash utility for bp_reg offset resolving. > >> --- > >> x86_64.c | 32 +++++++++++++++++++++++++------- > >> 1 file changed, 25 insertions(+), 7 deletions(-) > >> > >> diff --git a/x86_64.c b/x86_64.c > >> index 55648697baf3..d192f3bcdd20 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; > >> + ulong value = 0; > >> + req = &request; > >> > >> 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 +6739,28 @@ 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; > > > > How about use the newere values as default, and check the symbol data and set them as old ones if needed? > > Hmm, if change the order, the orc_fp_entry could not exist since it was introduced in 2025. Ok, unless you have some smarter idea, the patch looks good, please ignore the above comment. > OK, thanks Dave. I will take the original one. Thanks again for your comment and patch review! Thanks, Tao Liu > > Reviewed-by: Dave Young <yangrr.2009(a)tsinghua.org.cn&gt; > > Thanks >