Hi Konrad,
On 16/09/2016 18:38, Konrad Rzeszutek Wilk wrote:
To use as a common way of testing alternative patching for
livepatches. Both architectures have this FEATURE and the
test-cases can piggyback on that.
Suggested-by: Julien Grall
Signed-off-by: Konrad Rzeszutek Wilk
---
Cc: Julien Grall
Cc: Stefano Stabellini
Cc: Jan Beulich
Cc: Andrew Cooper
v3: New submission
v4: Move the LIVEPATCH_FEATURE to asm-x86/livepatch.h
---
xen/arch/arm/livepatch.c | 3 +++
xen/include/asm-arm/alternative.h | 2 ++
xen/include/asm-arm/cpufeature.h | 5 +
xen/include/asm-x86/livepatch.h | 1 +
xen/test/livepatch/xen_hello_world_func.c | 8 +---
5 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/xen/arch/arm/livepatch.c b/xen/arch/arm/livepatch.c
index 13d6c10..b771cb7 100644
--- a/xen/arch/arm/livepatch.c
+++ b/xen/arch/arm/livepatch.c
@@ -8,6 +8,7 @@
#include
#include
+#include
#include
#include
@@ -175,6 +176,8 @@ void __init arch_livepatch_init(void)
end = (void *)LIVEPATCH_VMAP_END;
vm_init_type(VMAP_XEN, start, end);
+
+cpus_set_cap(LIVEPATCH_FEATURE);
}
/*
diff --git a/xen/include/asm-arm/alternative.h
b/xen/include/asm-arm/alternative.h
index 6851217..cca5f17 100644
--- a/xen/include/asm-arm/alternative.h
+++ b/xen/include/asm-arm/alternative.h
@@ -165,6 +165,8 @@ static inline int apply_alternatives(void *start, size_t
lenght)
return 0;
}
+#define ALTERNATIVE(oldinstr, newinstr, ...) ""
+
Why this change? Nobody should ever use ALTERNATIVE when
CONFIG_ALTERNATIVE is not enabled. This is a call to have a Xen not
patched for a buggy hardware.
Not to mention that a void ALTERNATIVE is really buggy. We use
ALTERNATIVE to switch between two set of instructions. So we always need
at least one integrated in Xen.
#endif
#endif /* __ASM_ALTERNATIVE_H */
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index 66e930f..19e768b 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -40,7 +40,12 @@
#define ARM32_WORKAROUND_766422 2
#define ARM64_WORKAROUND_834220 3
+#ifdef CONFIG_LIVEPATCH
+#define LIVEPATCH_FEATURE 4
+#define ARM_NCAPS 5
+#else
#define ARM_NCAPS 4
+#endif
I would rather define the feature livepatch unconditionally to avoid the
definition of ARM_NCAPS twice.
diff --git a/xen/test/livepatch/xen_hello_world_func.c
b/xen/test/livepatch/xen_hello_world_func.c
index 6f53ab4..765a871 100644
--- a/xen/test/livepatch/xen_hello_world_func.c
+++ b/xen/test/livepatch/xen_hello_world_func.c
@@ -20,7 +20,6 @@ const char *xen_hello_world(void)
unsigned long tmp;
int rc;
-alternative(ASM_NOP8, ASM_NOP1, X86_FEATURE_LM);
Any reason to move the code later on?
/*
* Any BUG, or WARN_ON will contain symbol and payload name. Furthermore
* exceptions will be caught and processed properly.
@@ -28,8 +27,11 @@ const char *xen_hello_world(void)
rc = __get_user(tmp, non_canonical_addr);
BUG_ON(rc != -EFAULT);
#endif
-#ifdef CONFIG_ARM_64
-asm(ALTERNATIVE("nop", "nop", ARM64_WORKAROUND_CLEAN_CACHE));
+#ifdef CONFIG_ARM
+asm(ALTERNATIVE("nop", "nop", LIVEPATCH_FEATURE));
Ah, this is why you need a nop ALTERNATIVE. My comment above still
stands, this definition of ALTERNATIVE maybe be valid for your use case,
but it is invalid for most of the others.
+#endif
+#ifdef CONFIG_X86
+asm(ALTERNATIVE(ASM_NOP8, ASM_NOP1, LIVEPATCH_FEATURE));
#endif
return "Hello World";
}
Regards,
--
Julien Grall
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