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Refactor 5G-S-TMSI: harmonize 5G-S-TMSI handling with centralized helpers

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Centralizes 5G-S-TMSI bit manipulation logic for consistency and
maintainability. All manual bit operations replaced with documented
helper functions following TS 23.003 bit layout specification.

- Add helper functions for 5G-S-TMSI operations:

  * nr_construct_5g_s_tmsi_part1: 5G-S-TMSI construction is defined
    in 3GPP TS 23.003 and relevant at both gNB and UE side
    * Add helper functions to be later used in NG Paging
    * Adopt in NAS UE
  * nr_extract_5g_s_tmsi_part1() - extract Part1 (39 bits) from full
  * nr_extract_5g_s_tmsi_part2() - extract Part2 (9 bits) from full
  * nr_build_full_5g_s_tmsi() - reconstruct full from Part1+Part2
  * nr_deconstruct_5g_s_tmsi() - deconstruct into components
- Refactor manual bit manipulation to use helper functions:
  * asn1_msg.c: use nr_extract_5g_s_tmsi_part1() in RRCSetupRequest
  * asn1_msg.c: use nr_extract_5g_s_tmsi_part2() in RRCSetupComplete
  * rrc_gNB.c: use nr_build_full_5g_s_tmsi() when reconstructing from parts
  * rrc_gNB.c: use nr_deconstruct_5g_s_tmsi() when extracting components
- Optimize nr_construct_5g_s_tmsi_part1() to reuse extract function
This commit is contained in:
Guido Casati
2026-02-17 12:25:58 +01:00
parent 3c164ef138
commit f295252b2e
5 changed files with 77 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
common/utils/nr/nr_common.c
+56 -1
View File
@@ -1463,6 +1463,18 @@ uint64_t nr_construct_5g_s_tmsi(uint16_t amf_set_id, uint8_t amf_pointer, uint32
return ((uint64_t)amf_set_id << 38) | ((uint64_t)amf_pointer << 32) | m_tmsi;
}
/** @brief Extract 5G-S-TMSI-Part1 from full 5G-S-TMSI
* @param fiveg_s_tmsi Full 5G-S-TMSI (48 bits)
* @return 5G-S-TMSI-Part1 (rightmost 39 bits)
* @note 5G-S-TMSI-Part1 is the rightmost 39 bits of the full 5G-S-TMSI:
* - Bits 32-37: AMF Pointer (6 bits)
* - Bits 0-31: 5G-TMSI (32 bits)
* @ref 3GPP TS 23.003 */
uint64_t nr_extract_5g_s_tmsi_part1(const uint64_t fiveg_s_tmsi)
{
return fiveg_s_tmsi & ((1ULL << 39) - 1);
}
/** @brief Construct 5G-S-TMSI-Part1 from 5G-S-TMSI components
* @param amf_set_id AMF Set ID (10 bits)
* @param amf_pointer AMF Pointer (6 bits)
@@ -1476,5 +1488,48 @@ uint64_t nr_construct_5g_s_tmsi_part1(uint16_t amf_set_id, uint8_t amf_pointer,
{
// Construct full 5G-S-TMSI and extract Part1: rightmost 39 bits
uint64_t full_s_tmsi = nr_construct_5g_s_tmsi(amf_set_id, amf_pointer, m_tmsi);
return full_s_tmsi & ((1ULL << 39) - 1);
return nr_extract_5g_s_tmsi_part1(full_s_tmsi);
}
/** @brief Extract 5G-S-TMSI-Part2 from full 5G-S-TMSI
* @param fiveg_s_tmsi Full 5G-S-TMSI (48 bits)
* @return 5G-S-TMSI-Part2 (leftmost 9 bits)
* @note 5G-S-TMSI-Part2 is the leftmost 9 bits of the full 5G-S-TMSI:
* - Bits 39-47: AMF Set ID (9 bits)
* @ref 3GPP TS 23.003 */
uint16_t nr_extract_5g_s_tmsi_part2(const uint64_t fiveg_s_tmsi)
{
return (fiveg_s_tmsi >> 39) & ((1ULL << 9) - 1);
}
/** @brief Build full 5G-S-TMSI from Part1 and Part2
* @param part1 5G-S-TMSI-Part1 (rightmost 39 bits)
* @param part2 5G-S-TMSI-Part2 (leftmost 9 bits)
* @return Full 5G-S-TMSI (48 bits)
* @note Combines Part2 (leftmost 9 bits) and Part1 (rightmost 39 bits)
* @ref 3GPP TS 23.003 */
uint64_t nr_build_full_5g_s_tmsi(const uint64_t part1, const uint16_t part2)
{
return ((uint64_t)part2 << 39) | part1;
}
/** @brief Deconstruct full 5G-S-TMSI into its components
* @param fiveg_s_tmsi Full 5G-S-TMSI (48 bits)
* @param[out] amf_set_id Pointer to store AMF Set ID (10 bits)
* @param[out] amf_pointer Pointer to store AMF Pointer (6 bits)
* @param[out] m_tmsi Pointer to store 5G-TMSI (32 bits)
* @note The 5G-S-TMSI is deconstructed from a 48-bit value:
* - Bits 38-47: AMF Set ID (10 bits)
* - Bits 32-37: AMF Pointer (6 bits)
* - Bits 0-31: 5G-TMSI (32 bits)
* @ref 3GPP TS 23.003 */
void nr_deconstruct_5g_s_tmsi(const uint64_t fiveg_s_tmsi, uint16_t *amf_set_id, uint8_t *amf_pointer, uint32_t *m_tmsi)
{
DevAssert(amf_set_id != NULL);
DevAssert(amf_pointer != NULL);
DevAssert(m_tmsi != NULL);
*amf_set_id = fiveg_s_tmsi >> 38;
*amf_pointer = (fiveg_s_tmsi >> 32) & 0x3F;
*m_tmsi = fiveg_s_tmsi;
}
common/utils/nr/nr_common.h
+12
View File
@@ -360,6 +360,18 @@ uint64_t nr_construct_5g_s_tmsi(uint16_t amf_set_id, uint8_t amf_pointer, uint32
/** @brief Construct 5G-S-TMSI-Part1 from 5G-S-TMSI components */
uint64_t nr_construct_5g_s_tmsi_part1(uint16_t amf_set_id, uint8_t amf_pointer, uint32_t m_tmsi);
/** @brief Extract 5G-S-TMSI-Part1 from full 5G-S-TMSI */
uint64_t nr_extract_5g_s_tmsi_part1(const uint64_t fiveg_s_tmsi);
/** @brief Extract 5G-S-TMSI-Part2 from full 5G-S-TMSI */
uint16_t nr_extract_5g_s_tmsi_part2(const uint64_t fiveg_s_tmsi);
/** @brief Build full 5G-S-TMSI from Part1 and Part2 */
uint64_t nr_build_full_5g_s_tmsi(const uint64_t part1, const uint16_t part2);
/** @brief Deconstruct full 5G-S-TMSI into its components */
void nr_deconstruct_5g_s_tmsi(const uint64_t fiveg_s_tmsi, uint16_t *amf_set_id, uint8_t *amf_pointer, uint32_t *m_tmsi);
#define CEILIDIV(a,b) ((a+b-1)/b)
#define ROUNDIDIV(a,b) (((a<<1)+b)/(b<<1))
#define BOUNDED_EVAL(a, b, c) (min(c, max(a, b)))