2023-08-20 13:54:29

by GONG, Ruiqi

[permalink] [raw]
Subject: [PATCH] samples: ftrace: replace bti assembly with hint for older compiler

From: "GONG, Ruiqi" <[email protected]>

When cross-building the arm64 kernel with allmodconfig using GCC 9.4,
the following error occurs on multiple files under samples/ftrace/:

/tmp/ccPC1ODs.s: Assembler messages:
/tmp/ccPC1ODs.s:8: Error: selected processor does not support `bti c'

Fix this issue by replacing `bti c` with `hint 34`, which is compatible
for the older compiler.

Signed-off-by: GONG, Ruiqi <[email protected]>
---
samples/ftrace/ftrace-direct-modify.c | 4 ++--
samples/ftrace/ftrace-direct-multi-modify.c | 4 ++--
samples/ftrace/ftrace-direct-multi.c | 2 +-
samples/ftrace/ftrace-direct-too.c | 2 +-
samples/ftrace/ftrace-direct.c | 2 +-
5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
index e5ed08098ff3..e2a6a69352df 100644
--- a/samples/ftrace/ftrace-direct-modify.c
+++ b/samples/ftrace/ftrace-direct-modify.c
@@ -105,7 +105,7 @@ asm (
" .type my_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #16\n"
" stp x9, x30, [sp]\n"
" bl my_direct_func1\n"
@@ -117,7 +117,7 @@ asm (
" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #16\n"
" stp x9, x30, [sp]\n"
" bl my_direct_func2\n"
diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
index 292cff2b3f5d..2e349834d63c 100644
--- a/samples/ftrace/ftrace-direct-multi-modify.c
+++ b/samples/ftrace/ftrace-direct-multi-modify.c
@@ -112,7 +112,7 @@ asm (
" .type my_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #32\n"
" stp x9, x30, [sp]\n"
" str x0, [sp, #16]\n"
@@ -127,7 +127,7 @@ asm (
" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #32\n"
" stp x9, x30, [sp]\n"
" str x0, [sp, #16]\n"
diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
index b4391e08c913..9243dbfe4d0c 100644
--- a/samples/ftrace/ftrace-direct-multi.c
+++ b/samples/ftrace/ftrace-direct-multi.c
@@ -75,7 +75,7 @@ asm (
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #32\n"
" stp x9, x30, [sp]\n"
" str x0, [sp, #16]\n"
diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
index e9804c5307c0..e39c3563ae4e 100644
--- a/samples/ftrace/ftrace-direct-too.c
+++ b/samples/ftrace/ftrace-direct-too.c
@@ -81,7 +81,7 @@ asm (
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #48\n"
" stp x9, x30, [sp]\n"
" stp x0, x1, [sp, #16]\n"
diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
index 20f4a7caa810..32c477da1e9a 100644
--- a/samples/ftrace/ftrace-direct.c
+++ b/samples/ftrace/ftrace-direct.c
@@ -72,7 +72,7 @@ asm (
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:"
-" bti c\n"
+" hint 34\n" // bti c
" sub sp, sp, #32\n"
" stp x9, x30, [sp]\n"
" str x0, [sp, #16]\n"
--
2.25.1



2023-08-21 17:34:06

by Mark Rutland

[permalink] [raw]
Subject: Re: [PATCH] samples: ftrace: replace bti assembly with hint for older compiler

On Sun, Aug 20, 2023 at 07:15:09PM +0800, GONG, Ruiqi wrote:
> From: "GONG, Ruiqi" <[email protected]>
>
> When cross-building the arm64 kernel with allmodconfig using GCC 9.4,
> the following error occurs on multiple files under samples/ftrace/:
>
> /tmp/ccPC1ODs.s: Assembler messages:
> /tmp/ccPC1ODs.s:8: Error: selected processor does not support `bti c'
>
> Fix this issue by replacing `bti c` with `hint 34`, which is compatible
> for the older compiler.
>
> Signed-off-by: GONG, Ruiqi <[email protected]>

Sorry about this; I'd forgotten about earlier compilers when reviewing the
original patch. It's a bit unfortunate to have to hand-code this each time, but
I'm not sure that it'd actually be cleaner to have a macro.

For the moment, I reckon this is worth taking as-is.

Steve, are you happy to add:

Fixes: 8c3526fb86060cb5 ("arm64: ftrace: Add direct call trampoline samples support")
Acked-by: Mark Rutland <[email protected]>

... ?

Thanks,
Mark.

> ---
> samples/ftrace/ftrace-direct-modify.c | 4 ++--
> samples/ftrace/ftrace-direct-multi-modify.c | 4 ++--
> samples/ftrace/ftrace-direct-multi.c | 2 +-
> samples/ftrace/ftrace-direct-too.c | 2 +-
> samples/ftrace/ftrace-direct.c | 2 +-
> 5 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
> index e5ed08098ff3..e2a6a69352df 100644
> --- a/samples/ftrace/ftrace-direct-modify.c
> +++ b/samples/ftrace/ftrace-direct-modify.c
> @@ -105,7 +105,7 @@ asm (
> " .type my_tramp1, @function\n"
> " .globl my_tramp1\n"
> " my_tramp1:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #16\n"
> " stp x9, x30, [sp]\n"
> " bl my_direct_func1\n"
> @@ -117,7 +117,7 @@ asm (
> " .type my_tramp2, @function\n"
> " .globl my_tramp2\n"
> " my_tramp2:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #16\n"
> " stp x9, x30, [sp]\n"
> " bl my_direct_func2\n"
> diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
> index 292cff2b3f5d..2e349834d63c 100644
> --- a/samples/ftrace/ftrace-direct-multi-modify.c
> +++ b/samples/ftrace/ftrace-direct-multi-modify.c
> @@ -112,7 +112,7 @@ asm (
> " .type my_tramp1, @function\n"
> " .globl my_tramp1\n"
> " my_tramp1:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #32\n"
> " stp x9, x30, [sp]\n"
> " str x0, [sp, #16]\n"
> @@ -127,7 +127,7 @@ asm (
> " .type my_tramp2, @function\n"
> " .globl my_tramp2\n"
> " my_tramp2:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #32\n"
> " stp x9, x30, [sp]\n"
> " str x0, [sp, #16]\n"
> diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
> index b4391e08c913..9243dbfe4d0c 100644
> --- a/samples/ftrace/ftrace-direct-multi.c
> +++ b/samples/ftrace/ftrace-direct-multi.c
> @@ -75,7 +75,7 @@ asm (
> " .type my_tramp, @function\n"
> " .globl my_tramp\n"
> " my_tramp:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #32\n"
> " stp x9, x30, [sp]\n"
> " str x0, [sp, #16]\n"
> diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
> index e9804c5307c0..e39c3563ae4e 100644
> --- a/samples/ftrace/ftrace-direct-too.c
> +++ b/samples/ftrace/ftrace-direct-too.c
> @@ -81,7 +81,7 @@ asm (
> " .type my_tramp, @function\n"
> " .globl my_tramp\n"
> " my_tramp:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #48\n"
> " stp x9, x30, [sp]\n"
> " stp x0, x1, [sp, #16]\n"
> diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
> index 20f4a7caa810..32c477da1e9a 100644
> --- a/samples/ftrace/ftrace-direct.c
> +++ b/samples/ftrace/ftrace-direct.c
> @@ -72,7 +72,7 @@ asm (
> " .type my_tramp, @function\n"
> " .globl my_tramp\n"
> " my_tramp:"
> -" bti c\n"
> +" hint 34\n" // bti c
> " sub sp, sp, #32\n"
> " stp x9, x30, [sp]\n"
> " str x0, [sp, #16]\n"
> --
> 2.25.1
>