[PATCH v3 1/2] arm64: ssbd: explicitly depend on <linux/prctl.h>

[PATCH v3 1/2] arm64: ssbd: explicitly depend on <linux/prctl.h>

[Anisse Astier]

Fix ssbd.c which depends implicitly on asm/ptrace.h including
linux/prctl.h (through for example linux/compat.h, then linux/time.h,
linux/seqlock.h, linux/spinlock.h and linux/irqflags.h), and uses
PR_SPEC* defines.

This is an issue since we'll remove the include in the next commit.

Fixes: 9cdc0108baa8 ("arm64: ssbd: Add prctl interface for per-thread mitigation")
Cc: stable@vger.kernel.org
Signed-off-by: Anisse Astier <aastier@freebox.fr>
---
Contrary to what I said in the previous email, I can reproduce the build
error on Linus' master when ARM64_SSBD is enabled.

Changes since v2:
 - fix build when ARM64_SSBD is enabled with additionnal patch
Changes since v1:
 - made a bit more explicit that we copied defined symbols, in commit
   and code.
 - Use Fixes: tag in commit message

Thanks to Dave Martin and Will Deacon for the review, and Sasha Levin
for the auto-build bot.
---
 arch/arm64/kernel/ssbd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/ssbd.c b/arch/arm64/kernel/ssbd.c
index 885f13e58708..52cfc6148355 100644
--- a/arch/arm64/kernel/ssbd.c
+++ b/arch/arm64/kernel/ssbd.c
@@ -5,6 +5,7 @@
 
 #include <linux/compat.h>
 #include <linux/errno.h>
+#include <linux/prctl.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/thread_info.h>
-- 
2.19.1


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[PATCH v3 2/2] arm64/sve: <uapi/asm/ptrace.h> should not depend on <uapi/linux/prctl.h>

[Anisse Astier]

Otherwise this will create userspace build issues for any program
(strace, qemu) that includes both <sys/prctl.h> (with musl libc) and
<linux/ptrace.h> (which then includes <asm/ptrace.h>), like this:

	error: redefinition of 'struct prctl_mm_map'
	 struct prctl_mm_map {

See https://github.com/foundriesio/meta-lmp/commit/6d4a106e191b5d79c41b9ac78fd321316d3013c0
for a public example of people working around this issue.

Copying the defines is a bit imperfect here, but better than creating a
whole other header for just two defines that would never change, as part
of the kernel ABI.

This patch depends on patch "arm64: ssbd: explicitly depend on
<linux/prctl.h>" for kernel >= 4.18

Fixes: 43d4da2c45b2 ("arm64/sve: ptrace and ELF coredump support")
Cc: stable@vger.kernel.org
Signed-off-by: Anisse Astier <aastier@freebox.fr>
---
 arch/arm64/include/uapi/asm/ptrace.h | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
index 97c53203150b..e932284993d4 100644
--- a/arch/arm64/include/uapi/asm/ptrace.h
+++ b/arch/arm64/include/uapi/asm/ptrace.h
@@ -65,8 +65,6 @@
 
 #ifndef __ASSEMBLY__
 
-#include <linux/prctl.h>
-
 /*
  * User structures for general purpose, floating point and debug registers.
  */
@@ -113,10 +111,10 @@ struct user_sve_header {
 
 /*
  * Common SVE_PT_* flags:
- * These must be kept in sync with prctl interface in <linux/ptrace.h>
+ * These must be kept in sync with prctl interface in <linux/prctl.h>
  */
-#define SVE_PT_VL_INHERIT		(PR_SVE_VL_INHERIT >> 16)
-#define SVE_PT_VL_ONEXEC		(PR_SVE_SET_VL_ONEXEC >> 16)
+#define SVE_PT_VL_INHERIT		((1 << 17) /* PR_SVE_VL_INHERIT */ >> 16)
+#define SVE_PT_VL_ONEXEC		((1 << 18) /* PR_SVE_SET_VL_ONEXEC */ >> 16)
 
 
 /*
-- 
2.19.1


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Re: [PATCH v3 2/2] arm64/sve: <uapi/asm/ptrace.h> should not depend on <uapi/linux/prctl.h>

[Will Deacon]

On Mon, Jun 17, 2019 at 03:22:22PM +0200, Anisse Astier wrote:
> Otherwise this will create userspace build issues for any program
> (strace, qemu) that includes both <sys/prctl.h> (with musl libc) and
> <linux/ptrace.h> (which then includes <asm/ptrace.h>), like this:
> 
> 	error: redefinition of 'struct prctl_mm_map'
> 	 struct prctl_mm_map {
> 
> See https://github.com/foundriesio/meta-lmp/commit/6d4a106e191b5d79c41b9ac78fd321316d3013c0
> for a public example of people working around this issue.
> 
> Copying the defines is a bit imperfect here, but better than creating a
> whole other header for just two defines that would never change, as part
> of the kernel ABI.
> 
> This patch depends on patch "arm64: ssbd: explicitly depend on
> <linux/prctl.h>" for kernel >= 4.18
> 
> Fixes: 43d4da2c45b2 ("arm64/sve: ptrace and ELF coredump support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Anisse Astier <aastier@freebox.fr>
> ---
>  arch/arm64/include/uapi/asm/ptrace.h | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)

I've pushed these two out to the arm64 fixes branch [1], with Dave's Ack
on this one. Note that I reworked the commit messages a bit to explain
better what's going on.

Cheers,

Will

[1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/fixes

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