lib: sbi_scratch: Apply bounds check to platform hart_count

The internal limit on the number of harts is SBI_HARTMASK_MAX_BITS, as
this value determines the size of various bitmaps and arrays (including
hartindex_to_hartid_table and hartindex_to_scratch_table). Clamp the
value provided by the platform, and drop the extra array element.

Update the documentation to indicate that hart_index2id must be sized
based on hart_count, and that hart indexes must be contiguous. As of
commit 5e90e54a1a53 ("lib: utils:Check that hartid is valid"), there is
no restriction on the valid hart ID values.

Signed-off-by: Samuel Holland <[email protected]>
Reviewed-by: Anup Patel <[email protected]>

2 files changed, 12 insertions, 13 deletions

diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
index 6d5fbc7d..5e50c997 100644
--- a/include/sbi/sbi_platform.h
+++ b/include/sbi/sbi_platform.h
@@ -169,7 +169,7 @@ struct sbi_platform {
 	char name[64];
 	/** Supported features */
 	u64 features;
-	/** Total number of HARTs */
+	/** Total number of HARTs (at most SBI_HARTMASK_MAX_BITS) */
 	u32 hart_count;
 	/** Per-HART stack size for exception/interrupt handling */
 	u32 hart_stack_size;
@@ -184,17 +184,12 @@ struct sbi_platform {
 	/**
 	 * HART index to HART id table
 	 *
-	 * For used HART index <abc>:
+	 * If hart_index2id != NULL then the table must contain a mapping
+	 * for each HART index 0 <= <abc> < hart_count:
 	 *     hart_index2id[<abc>] = some HART id
-	 * For unused HART index <abc>:
-	 *     hart_index2id[<abc>] = -1U
 	 *
 	 * If hart_index2id == NULL then we assume identity mapping
 	 *     hart_index2id[<abc>] = <abc>
-	 *
-	 * We have only two restrictions:
-	 * 1. HART index < sbi_platform hart_count
-	 * 2. HART id < SBI_HARTMASK_MAX_BITS
 	 */
 	const u32 *hart_index2id;
 };
diff --git a/lib/sbi/sbi_scratch.c b/lib/sbi/sbi_scratch.c
index ccbbc68e..5a9e935b 100644
--- a/lib/sbi/sbi_scratch.c
+++ b/lib/sbi/sbi_scratch.c
@@ -15,8 +15,8 @@
 #include <sbi/sbi_string.h>
 
 u32 last_hartindex_having_scratch = 0;
-u32 hartindex_to_hartid_table[SBI_HARTMASK_MAX_BITS + 1] = { -1U };
-struct sbi_scratch *hartindex_to_scratch_table[SBI_HARTMASK_MAX_BITS + 1] = { 0 };
+u32 hartindex_to_hartid_table[SBI_HARTMASK_MAX_BITS] = { -1U };
+struct sbi_scratch *hartindex_to_scratch_table[SBI_HARTMASK_MAX_BITS] = { 0 };
 
 static spinlock_t extra_lock = SPIN_LOCK_INITIALIZER;
 static unsigned long extra_offset = SBI_SCRATCH_EXTRA_SPACE_OFFSET;
@@ -36,17 +36,21 @@ typedef struct sbi_scratch *(*hartid2scratch)(ulong hartid, ulong hartindex);
 
 int sbi_scratch_init(struct sbi_scratch *scratch)
 {
-	u32 i, h;
+	u32 i, h, hart_count;
 	const struct sbi_platform *plat = sbi_platform_ptr(scratch);
 
-	for (i = 0; i < plat->hart_count; i++) {
+	hart_count = plat->hart_count;
+	if (hart_count > SBI_HARTMASK_MAX_BITS)
+		hart_count = SBI_HARTMASK_MAX_BITS;
+
+	for (i = 0; i < hart_count; i++) {
 		h = (plat->hart_index2id) ? plat->hart_index2id[i] : i;
 		hartindex_to_hartid_table[i] = h;
 		hartindex_to_scratch_table[i] =
 			((hartid2scratch)scratch->hartid_to_scratch)(h, i);
 	}
 
-	last_hartindex_having_scratch = plat->hart_count - 1;
+	last_hartindex_having_scratch = hart_count - 1;
 
 	return 0;
 }