Re: [PATCH] sparc: Replace one-element array with flexible array member

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On 11/11/24 14:01, Thorsten Blum wrote:
Replace the deprecated one-element array with a modern flexible array
member in the struct hvtramp_descr.

Additionally, 15 unnecessary bytes are allocated for hdesc, but instead

15? unnecessary?

of fixing the parentheses in the open-coded version, use struct_size()
to calculate the correct number of bytes.

Link: https://github.com/KSPP/linux/issues/79
Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxx>
---
  arch/sparc/include/asm/hvtramp.h | 2 +-
  arch/sparc/kernel/smp_64.c       | 4 +---
  2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/include/asm/hvtramp.h b/arch/sparc/include/asm/hvtramp.h
index 688ea43af0f5..ce2453ea4f2b 100644
--- a/arch/sparc/include/asm/hvtramp.h
+++ b/arch/sparc/include/asm/hvtramp.h
@@ -17,7 +17,7 @@ struct hvtramp_descr {
  	__u64			fault_info_va;
  	__u64			fault_info_pa;
  	__u64			thread_reg;
-	struct hvtramp_mapping	maps[1];
+	struct hvtramp_mapping	maps[];
  };

It seems this struct is a candidate for `__counted_by()`

void hv_cpu_startup(unsigned long hvdescr_pa);
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index e40c395db202..24d980220bf1 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -297,9 +297,7 @@ static void ldom_startcpu_cpuid(unsigned int cpu, unsigned long thread_reg,
  	unsigned long hv_err;
  	int i;
- hdesc = kzalloc(sizeof(*hdesc) +
-			(sizeof(struct hvtramp_mapping) *
-			 num_kernel_image_mappings - 1),
+	hdesc = kzalloc(struct_size(hdesc, maps, num_kernel_image_mappings - 1),
  			GFP_KERNEL);

Now the code is broken because it's allocating `num_kernel_image_mappings - 1`
elements instead of `num_kernel_image_mappings`.

--
Gustavo




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