[PATCH] objtool: Support Clang RAX DRAP sequence

[PATCH] objtool: Support Clang RAX DRAP sequence

[Josh Poimboeuf]

Recent Clang can use RAX as a temporary register for the DRAP stack
alignment sequence.  Add support for that.

Fixes the following warning:

  vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0

Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/orc_types.h       | 1 +
 arch/x86/kernel/unwind_orc.c           | 8 ++++++++
 tools/arch/x86/include/asm/orc_types.h | 1 +
 tools/objtool/arch/x86/decode.c        | 3 +++
 tools/objtool/arch/x86/orc.c           | 5 +++++
 5 files changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index e0125afa53fb..b3cc7970fa54 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -37,6 +37,7 @@
 #define ORC_REG_R13			7
 #define ORC_REG_BP_INDIRECT		8
 #define ORC_REG_SP_INDIRECT		9
+#define ORC_REG_AX			10
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index f610fde2d5c4..32f7e918d3d9 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -578,6 +578,14 @@ bool unwind_next_frame(struct unwind_state *state)
 		}
 		break;
 
+	case ORC_REG_AX:
+		if (!get_reg(state, offsetof(struct pt_regs, ax), &sp)) {
+			orc_warn_current("missing AX value at %pB\n",
+					 (void *)state->ip);
+			goto err;
+		}
+		break;
+
 	default:
 		orc_warn("unknown SP base reg %d at %pB\n",
 			 orc->sp_reg, (void *)state->ip);
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index e0125afa53fb..b3cc7970fa54 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -37,6 +37,7 @@
 #define ORC_REG_R13			7
 #define ORC_REG_BP_INDIRECT		8
 #define ORC_REG_SP_INDIRECT		9
+#define ORC_REG_AX			10
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index c5817829cdfa..5931b2393bd8 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -896,6 +896,9 @@ int arch_decode_hint_reg(u8 sp_reg, int *base)
 	case ORC_REG_DX:
 		*base = CFI_DX;
 		break;
+	case ORC_REG_AX:
+		*base = CFI_AX;
+		break;
 	default:
 		return -1;
 	}
diff --git a/tools/objtool/arch/x86/orc.c b/tools/objtool/arch/x86/orc.c
index 735e150ca6b7..5494bb450ab5 100644
--- a/tools/objtool/arch/x86/orc.c
+++ b/tools/objtool/arch/x86/orc.c
@@ -70,6 +70,9 @@ int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruct
 	case CFI_DX:
 		orc->sp_reg = ORC_REG_DX;
 		break;
+	case CFI_AX:
+		orc->sp_reg = ORC_REG_AX;
+		break;
 	default:
 		ERROR_INSN(insn, "unknown CFA base reg %d", cfi->cfa.base);
 		return -1;
@@ -138,6 +141,8 @@ static const char *reg_name(unsigned int reg)
 		return "bp(ind)";
 	case ORC_REG_SP_INDIRECT:
 		return "sp(ind)";
+	case ORC_REG_AX:
+		return "ax";
 	default:
 		return "?";
 	}
-- 
2.53.0

Re: [PATCH] objtool: Support Clang RAX DRAP sequence

[Peter Zijlstra]

On Mon, Mar 16, 2026 at 05:47:56PM -0700, Josh Poimboeuf wrote:
> Recent Clang can use RAX as a temporary register for the DRAP stack
> alignment sequence.  Add support for that.
> 
> Fixes the following warning:
> 
>   vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0
> 
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  arch/x86/include/asm/orc_types.h       | 1 +
>  arch/x86/kernel/unwind_orc.c           | 8 ++++++++
>  tools/arch/x86/include/asm/orc_types.h | 1 +
>  tools/objtool/arch/x86/decode.c        | 3 +++
>  tools/objtool/arch/x86/orc.c           | 5 +++++
>  5 files changed, 18 insertions(+)
> 
> diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
> index e0125afa53fb..b3cc7970fa54 100644
> --- a/arch/x86/include/asm/orc_types.h
> +++ b/arch/x86/include/asm/orc_types.h
> @@ -37,6 +37,7 @@
>  #define ORC_REG_R13			7
>  #define ORC_REG_BP_INDIRECT		8
>  #define ORC_REG_SP_INDIRECT		9
> +#define ORC_REG_AX			10
>  #define ORC_REG_MAX			15

I'm 'annoyed' at the placement of that register. I know its not
important, but I can't silence my OCD saying that AX should come before
DX.

Also, SP comes before BP and both before DI.

Something like so perhaps?

---
diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index e0125afa53fb..5df398761c70 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -28,15 +28,19 @@
  * and GCC realigned stacks.
  */
 #define ORC_REG_UNDEFINED		0
-#define ORC_REG_PREV_SP			1
+
+#define ORC_REG_AX			1
 #define ORC_REG_DX			2
-#define ORC_REG_DI			3
+#define ORC_REG_SP			3
 #define ORC_REG_BP			4
-#define ORC_REG_SP			5
+#define ORC_REG_DI			5
 #define ORC_REG_R10			6
 #define ORC_REG_R13			7
-#define ORC_REG_BP_INDIRECT		8
+
+#define ORC_REG_PREV_SP			8
 #define ORC_REG_SP_INDIRECT		9
+#define ORC_REG_BP_INDIRECT		10
+
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0

Re: [PATCH] objtool: Support Clang RAX DRAP sequence

[Josh Poimboeuf]

On Tue, Mar 17, 2026 at 09:18:25AM +0100, Peter Zijlstra wrote:
> On Mon, Mar 16, 2026 at 05:47:56PM -0700, Josh Poimboeuf wrote:
> > Recent Clang can use RAX as a temporary register for the DRAP stack
> > alignment sequence.  Add support for that.
> > 
> > Fixes the following warning:
> > 
> >   vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0
> > 
> > Reported-by: Arnd Bergmann <arnd@arndb.de>
> > Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com
> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> > ---
> >  arch/x86/include/asm/orc_types.h       | 1 +
> >  arch/x86/kernel/unwind_orc.c           | 8 ++++++++
> >  tools/arch/x86/include/asm/orc_types.h | 1 +
> >  tools/objtool/arch/x86/decode.c        | 3 +++
> >  tools/objtool/arch/x86/orc.c           | 5 +++++
> >  5 files changed, 18 insertions(+)
> > 
> > diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
> > index e0125afa53fb..b3cc7970fa54 100644
> > --- a/arch/x86/include/asm/orc_types.h
> > +++ b/arch/x86/include/asm/orc_types.h
> > @@ -37,6 +37,7 @@
> >  #define ORC_REG_R13			7
> >  #define ORC_REG_BP_INDIRECT		8
> >  #define ORC_REG_SP_INDIRECT		9
> > +#define ORC_REG_AX			10
> >  #define ORC_REG_MAX			15
> 
> I'm 'annoyed' at the placement of that register. I know its not
> important, but I can't silence my OCD saying that AX should come before
> DX.
> 
> Also, SP comes before BP and both before DI.
> 
> Something like so perhaps?

That bothered me too, but I was trying to keep the diffstat down.  But
sure, why not...

What about the switch statements?  Should we reorder them too while at
it?  If so, starting to feel like a separate patch.

-- 
Josh

Re: [PATCH] objtool: Support Clang RAX DRAP sequence

[Peter Zijlstra]

On Tue, Mar 17, 2026 at 08:30:59AM -0700, Josh Poimboeuf wrote:
> On Tue, Mar 17, 2026 at 09:18:25AM +0100, Peter Zijlstra wrote:
> > On Mon, Mar 16, 2026 at 05:47:56PM -0700, Josh Poimboeuf wrote:
> > > Recent Clang can use RAX as a temporary register for the DRAP stack
> > > alignment sequence.  Add support for that.
> > > 
> > > Fixes the following warning:
> > > 
> > >   vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0
> > > 
> > > Reported-by: Arnd Bergmann <arnd@arndb.de>
> > > Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com
> > > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> > > ---
> > >  arch/x86/include/asm/orc_types.h       | 1 +
> > >  arch/x86/kernel/unwind_orc.c           | 8 ++++++++
> > >  tools/arch/x86/include/asm/orc_types.h | 1 +
> > >  tools/objtool/arch/x86/decode.c        | 3 +++
> > >  tools/objtool/arch/x86/orc.c           | 5 +++++
> > >  5 files changed, 18 insertions(+)
> > > 
> > > diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
> > > index e0125afa53fb..b3cc7970fa54 100644
> > > --- a/arch/x86/include/asm/orc_types.h
> > > +++ b/arch/x86/include/asm/orc_types.h
> > > @@ -37,6 +37,7 @@
> > >  #define ORC_REG_R13			7
> > >  #define ORC_REG_BP_INDIRECT		8
> > >  #define ORC_REG_SP_INDIRECT		9
> > > +#define ORC_REG_AX			10
> > >  #define ORC_REG_MAX			15
> > 
> > I'm 'annoyed' at the placement of that register. I know its not
> > important, but I can't silence my OCD saying that AX should come before
> > DX.
> > 
> > Also, SP comes before BP and both before DI.
> > 
> > Something like so perhaps?
> 
> That bothered me too, but I was trying to keep the diffstat down.  But
> sure, why not...
> 
> What about the switch statements?  Should we reorder them too while at
> it?  If so, starting to feel like a separate patch.

Agreed, switch statement order should match the definition order. And
yes separate patch is fine.

Re: [PATCH] objtool: Support Clang RAX DRAP sequence

[Josh Poimboeuf]

On Tue, Mar 17, 2026 at 09:35:02PM +0100, Peter Zijlstra wrote:
> On Tue, Mar 17, 2026 at 08:30:59AM -0700, Josh Poimboeuf wrote:
> > On Tue, Mar 17, 2026 at 09:18:25AM +0100, Peter Zijlstra wrote:
> > > On Mon, Mar 16, 2026 at 05:47:56PM -0700, Josh Poimboeuf wrote:
> > > > Recent Clang can use RAX as a temporary register for the DRAP stack
> > > > alignment sequence.  Add support for that.
> > > > 
> > > > Fixes the following warning:
> > > > 
> > > >   vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0
> > > > 
> > > > Reported-by: Arnd Bergmann <arnd@arndb.de>
> > > > Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com
> > > > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> > > > ---
> > > >  arch/x86/include/asm/orc_types.h       | 1 +
> > > >  arch/x86/kernel/unwind_orc.c           | 8 ++++++++
> > > >  tools/arch/x86/include/asm/orc_types.h | 1 +
> > > >  tools/objtool/arch/x86/decode.c        | 3 +++
> > > >  tools/objtool/arch/x86/orc.c           | 5 +++++
> > > >  5 files changed, 18 insertions(+)
> > > > 
> > > > diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
> > > > index e0125afa53fb..b3cc7970fa54 100644
> > > > --- a/arch/x86/include/asm/orc_types.h
> > > > +++ b/arch/x86/include/asm/orc_types.h
> > > > @@ -37,6 +37,7 @@
> > > >  #define ORC_REG_R13			7
> > > >  #define ORC_REG_BP_INDIRECT		8
> > > >  #define ORC_REG_SP_INDIRECT		9
> > > > +#define ORC_REG_AX			10
> > > >  #define ORC_REG_MAX			15
> > > 
> > > I'm 'annoyed' at the placement of that register. I know its not
> > > important, but I can't silence my OCD saying that AX should come before
> > > DX.
> > > 
> > > Also, SP comes before BP and both before DI.
> > > 
> > > Something like so perhaps?
> > 
> > That bothered me too, but I was trying to keep the diffstat down.  But
> > sure, why not...
> > 
> > What about the switch statements?  Should we reorder them too while at
> > it?  If so, starting to feel like a separate patch.
> 
> Agreed, switch statement order should match the definition order. And
> yes separate patch is fine.

Ok, we can add the following on top:

---8<---

From: Josh Poimboeuf <jpoimboe@kernel.org>
Subject: [PATCH] objtool/x86: Reorder ORC register numbering

Reorder the ORC register values so their ordering matches the x86
instruction set register encodings.

No functional change intended.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/orc_types.h       | 10 +++---
 arch/x86/kernel/unwind_orc.c           | 48 +++++++++++++++-----------
 tools/arch/x86/include/asm/orc_types.h | 10 +++---
 tools/objtool/arch/x86/decode.c        | 21 ++++++-----
 tools/objtool/arch/x86/orc.c           | 36 +++++++++----------
 5 files changed, 67 insertions(+), 58 deletions(-)

diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index b3cc7970fa54..5837c2bb277f 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -28,16 +28,16 @@
  * and GCC realigned stacks.
  */
 #define ORC_REG_UNDEFINED		0
-#define ORC_REG_PREV_SP			1
+#define ORC_REG_AX			1
 #define ORC_REG_DX			2
-#define ORC_REG_DI			3
+#define ORC_REG_SP			3
 #define ORC_REG_BP			4
-#define ORC_REG_SP			5
+#define ORC_REG_DI			5
 #define ORC_REG_R10			6
 #define ORC_REG_R13			7
-#define ORC_REG_BP_INDIRECT		8
+#define ORC_REG_PREV_SP			8
 #define ORC_REG_SP_INDIRECT		9
-#define ORC_REG_AX			10
+#define ORC_REG_BP_INDIRECT		10
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 32f7e918d3d9..6407bc9256bf 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -546,25 +546,15 @@ bool unwind_next_frame(struct unwind_state *state)
 		indirect = true;
 		break;
 
-	case ORC_REG_R10:
-		if (!get_reg(state, offsetof(struct pt_regs, r10), &sp)) {
-			orc_warn_current("missing R10 value at %pB\n",
-					 (void *)state->ip);
-			goto err;
-		}
-		break;
+	/*
+	 * Any of the below registers may temporarily hold the stack pointer,
+	 * typically during a DRAP stack realignment sequence or some other
+	 * stack swizzle.
+	 */
 
-	case ORC_REG_R13:
-		if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) {
-			orc_warn_current("missing R13 value at %pB\n",
-					 (void *)state->ip);
-			goto err;
-		}
-		break;
-
-	case ORC_REG_DI:
-		if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) {
-			orc_warn_current("missing RDI value at %pB\n",
+	case ORC_REG_AX:
+		if (!get_reg(state, offsetof(struct pt_regs, ax), &sp)) {
+			orc_warn_current("missing AX value at %pB\n",
 					 (void *)state->ip);
 			goto err;
 		}
@@ -578,9 +568,25 @@ bool unwind_next_frame(struct unwind_state *state)
 		}
 		break;
 
-	case ORC_REG_AX:
-		if (!get_reg(state, offsetof(struct pt_regs, ax), &sp)) {
-			orc_warn_current("missing AX value at %pB\n",
+	case ORC_REG_DI:
+		if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) {
+			orc_warn_current("missing RDI value at %pB\n",
+					 (void *)state->ip);
+			goto err;
+		}
+		break;
+
+	case ORC_REG_R10:
+		if (!get_reg(state, offsetof(struct pt_regs, r10), &sp)) {
+			orc_warn_current("missing R10 value at %pB\n",
+					 (void *)state->ip);
+			goto err;
+		}
+		break;
+
+	case ORC_REG_R13:
+		if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) {
+			orc_warn_current("missing R13 value at %pB\n",
 					 (void *)state->ip);
 			goto err;
 		}
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index b3cc7970fa54..5837c2bb277f 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -28,16 +28,16 @@
  * and GCC realigned stacks.
  */
 #define ORC_REG_UNDEFINED		0
-#define ORC_REG_PREV_SP			1
+#define ORC_REG_AX			1
 #define ORC_REG_DX			2
-#define ORC_REG_DI			3
+#define ORC_REG_SP			3
 #define ORC_REG_BP			4
-#define ORC_REG_SP			5
+#define ORC_REG_DI			5
 #define ORC_REG_R10			6
 #define ORC_REG_R13			7
-#define ORC_REG_BP_INDIRECT		8
+#define ORC_REG_PREV_SP			8
 #define ORC_REG_SP_INDIRECT		9
-#define ORC_REG_AX			10
+#define ORC_REG_BP_INDIRECT		10
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 5931b2393bd8..350b8ee6e776 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -875,14 +875,20 @@ int arch_decode_hint_reg(u8 sp_reg, int *base)
 	case ORC_REG_UNDEFINED:
 		*base = CFI_UNDEFINED;
 		break;
+	case ORC_REG_AX:
+		*base = CFI_AX;
+		break;
+	case ORC_REG_DX:
+		*base = CFI_DX;
+		break;
 	case ORC_REG_SP:
 		*base = CFI_SP;
 		break;
 	case ORC_REG_BP:
 		*base = CFI_BP;
 		break;
-	case ORC_REG_SP_INDIRECT:
-		*base = CFI_SP_INDIRECT;
+	case ORC_REG_DI:
+		*base = CFI_DI;
 		break;
 	case ORC_REG_R10:
 		*base = CFI_R10;
@@ -890,14 +896,11 @@ int arch_decode_hint_reg(u8 sp_reg, int *base)
 	case ORC_REG_R13:
 		*base = CFI_R13;
 		break;
-	case ORC_REG_DI:
-		*base = CFI_DI;
+	case ORC_REG_SP_INDIRECT:
+		*base = CFI_SP_INDIRECT;
 		break;
-	case ORC_REG_DX:
-		*base = CFI_DX;
-		break;
-	case ORC_REG_AX:
-		*base = CFI_AX;
+	case ORC_REG_BP_INDIRECT:
+		*base = CFI_BP_INDIRECT;
 		break;
 	default:
 		return -1;
diff --git a/tools/objtool/arch/x86/orc.c b/tools/objtool/arch/x86/orc.c
index 5494bb450ab5..eff078ecc945 100644
--- a/tools/objtool/arch/x86/orc.c
+++ b/tools/objtool/arch/x86/orc.c
@@ -46,17 +46,20 @@ int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruct
 	orc->signal = cfi->signal;
 
 	switch (cfi->cfa.base) {
+	case CFI_AX:
+		orc->sp_reg = ORC_REG_AX;
+		break;
+	case CFI_DX:
+		orc->sp_reg = ORC_REG_DX;
+		break;
 	case CFI_SP:
 		orc->sp_reg = ORC_REG_SP;
 		break;
-	case CFI_SP_INDIRECT:
-		orc->sp_reg = ORC_REG_SP_INDIRECT;
-		break;
 	case CFI_BP:
 		orc->sp_reg = ORC_REG_BP;
 		break;
-	case CFI_BP_INDIRECT:
-		orc->sp_reg = ORC_REG_BP_INDIRECT;
+	case CFI_DI:
+		orc->sp_reg = ORC_REG_DI;
 		break;
 	case CFI_R10:
 		orc->sp_reg = ORC_REG_R10;
@@ -64,14 +67,11 @@ int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruct
 	case CFI_R13:
 		orc->sp_reg = ORC_REG_R13;
 		break;
-	case CFI_DI:
-		orc->sp_reg = ORC_REG_DI;
+	case CFI_SP_INDIRECT:
+		orc->sp_reg = ORC_REG_SP_INDIRECT;
 		break;
-	case CFI_DX:
-		orc->sp_reg = ORC_REG_DX;
-		break;
-	case CFI_AX:
-		orc->sp_reg = ORC_REG_AX;
+	case CFI_BP_INDIRECT:
+		orc->sp_reg = ORC_REG_BP_INDIRECT;
 		break;
 	default:
 		ERROR_INSN(insn, "unknown CFA base reg %d", cfi->cfa.base);
@@ -125,24 +125,24 @@ static const char *reg_name(unsigned int reg)
 	switch (reg) {
 	case ORC_REG_PREV_SP:
 		return "prevsp";
+	case ORC_REG_AX:
+		return "ax";
 	case ORC_REG_DX:
 		return "dx";
-	case ORC_REG_DI:
-		return "di";
 	case ORC_REG_BP:
 		return "bp";
 	case ORC_REG_SP:
 		return "sp";
+	case ORC_REG_DI:
+		return "di";
 	case ORC_REG_R10:
 		return "r10";
 	case ORC_REG_R13:
 		return "r13";
-	case ORC_REG_BP_INDIRECT:
-		return "bp(ind)";
 	case ORC_REG_SP_INDIRECT:
 		return "sp(ind)";
-	case ORC_REG_AX:
-		return "ax";
+	case ORC_REG_BP_INDIRECT:
+		return "bp(ind)";
 	default:
 		return "?";
 	}
-- 
2.53.0

Re: [PATCH] objtool: Support Clang RAX DRAP sequence

[Peter Zijlstra]

On Tue, Mar 17, 2026 at 03:44:47PM -0700, Josh Poimboeuf wrote:
> Ok, we can add the following on top:
> 
> ---8<---
> 
> From: Josh Poimboeuf <jpoimboe@kernel.org>
> Subject: [PATCH] objtool/x86: Reorder ORC register numbering
> 
> Reorder the ORC register values so their ordering matches the x86
> instruction set register encodings.
> 
> No functional change intended.
> 
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Excellent, thanks!

[tip: objtool/core] objtool: Support Clang RAX DRAP sequence

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     96f3b16a9de552538b810f773645d43f3b661b50
Gitweb:        https://git.kernel.org/tip/96f3b16a9de552538b810f773645d43f3b661b50
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 16 Mar 2026 17:47:56 -07:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 18 Mar 2026 09:38:52 +01:00

objtool: Support Clang RAX DRAP sequence

Recent Clang can use RAX as a temporary register for the DRAP stack
alignment sequence.  Add support for that.

Fixes the following warning:

  vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0

Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/3f33dc720b83dc6d3a2b7094f75a5c90a0b1cbc5.1773708458.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/orc_types.h       | 1 +
 arch/x86/kernel/unwind_orc.c           | 8 ++++++++
 tools/arch/x86/include/asm/orc_types.h | 1 +
 tools/objtool/arch/x86/decode.c        | 3 +++
 tools/objtool/arch/x86/orc.c           | 5 +++++
 5 files changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index e0125af..b3cc797 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -37,6 +37,7 @@
 #define ORC_REG_R13			7
 #define ORC_REG_BP_INDIRECT		8
 #define ORC_REG_SP_INDIRECT		9
+#define ORC_REG_AX			10
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index f610fde..32f7e91 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -578,6 +578,14 @@ bool unwind_next_frame(struct unwind_state *state)
 		}
 		break;
 
+	case ORC_REG_AX:
+		if (!get_reg(state, offsetof(struct pt_regs, ax), &sp)) {
+			orc_warn_current("missing AX value at %pB\n",
+					 (void *)state->ip);
+			goto err;
+		}
+		break;
+
 	default:
 		orc_warn("unknown SP base reg %d at %pB\n",
 			 orc->sp_reg, (void *)state->ip);
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index e0125af..b3cc797 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -37,6 +37,7 @@
 #define ORC_REG_R13			7
 #define ORC_REG_BP_INDIRECT		8
 #define ORC_REG_SP_INDIRECT		9
+#define ORC_REG_AX			10
 #define ORC_REG_MAX			15
 
 #define ORC_TYPE_UNDEFINED		0
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 73bfea2..c3a10f3 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -912,6 +912,9 @@ int arch_decode_hint_reg(u8 sp_reg, int *base)
 	case ORC_REG_DX:
 		*base = CFI_DX;
 		break;
+	case ORC_REG_AX:
+		*base = CFI_AX;
+		break;
 	default:
 		return -1;
 	}
diff --git a/tools/objtool/arch/x86/orc.c b/tools/objtool/arch/x86/orc.c
index 735e150..5494bb4 100644
--- a/tools/objtool/arch/x86/orc.c
+++ b/tools/objtool/arch/x86/orc.c
@@ -70,6 +70,9 @@ int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruct
 	case CFI_DX:
 		orc->sp_reg = ORC_REG_DX;
 		break;
+	case CFI_AX:
+		orc->sp_reg = ORC_REG_AX;
+		break;
 	default:
 		ERROR_INSN(insn, "unknown CFA base reg %d", cfi->cfa.base);
 		return -1;
@@ -138,6 +141,8 @@ static const char *reg_name(unsigned int reg)
 		return "bp(ind)";
 	case ORC_REG_SP_INDIRECT:
 		return "sp(ind)";
+	case ORC_REG_AX:
+		return "ax";
 	default:
 		return "?";
 	}