Current get_frame_info implementation works on word boundary, this
can lead to alignment and endian issues in microMIPS/MIPS16 mode,
due to:
1. MIPS16 instructions can be 16bit or 32bit
2. MIPS16 32bit instructions may not be on the word boundary
3. MIPS16 instructions are placed in 32-bit memory element, in
endian-dependent order.
Example:
insn1 = 16bit => word1, hword[0]
insn2 = 32bit => word1, hword[1], word2, hword[0]
insn3 = 16bit => word2, hword[1]
Big Endian
hword[0] hword[1] hword[0] hword[1]
+-------------+-------------+-------------+-------------+
| insn1 | insn2 | insn2' | insn3 |
+-------------+-------------+-------------+-------------+
31 word1 0 31 word2 0
Little Endian
hword[1] hword[0] hword[1] hword[0]
+-------------+-------------+-------------+-------------+
| insn2 | insn1 | insn3 | insn2' |
+-------------+-------------+-------------+-------------+
31 word1 0 31 word2 0
This patch refactors microMIPS get_frame_info by implementing
fetch_instruction() to fetch instructions on word boundary, and
MIPS16_fetch_halfword() to assemble halfwords into 16bit/32bit MIPS16
instructions for further processing.
This patch also fixes sibling call handling and schedule_mfi
initialization for microMIPS.
Signed-off-by: Tony Wu <tung7970@xxxxxxxxx>
Cc: Steven J. Hill <Steven.Hill@xxxxxxxxxx>
---
arch/mips/kernel/process.c | 214 +++++++++++++++++++++++++++++---------------
1 file changed, 141 insertions(+), 73 deletions(-)
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index c6a041d..c335a7f 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -211,14 +211,17 @@ struct mips_frame_info {
int pc_offset;
};
+#ifdef CONFIG_CPU_MICROMIPS
+#define J_TARGET(pc,target) \
+ (((unsigned long)(pc) & 0xf8000000) | ((target) << 1))
+#else
#define J_TARGET(pc,target) \
(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
+#endif
static inline int is_ra_save_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
- union mips_instruction mmi;
-
/*
* swsp ra,offset
* swm16 reglist,offset(sp)
@@ -228,24 +231,17 @@ static inline int is_ra_save_ins(union mips_instruction *ip)
*
* microMIPS is way more fun...
*/
- if (mm_insn_16bit(ip->halfword[0])) {
- mmi.word = (ip->halfword[0] << 16);
- return ((mmi.mm16_r5_format.opcode == mm_swsp16_op &&
- mmi.mm16_r5_format.rt == 31) ||
- (mmi.mm16_m_format.opcode == mm_pool16c_op &&
- mmi.mm16_m_format.func == mm_swm16_op));
- }
- else {
- mmi.halfword[0] = ip->halfword[1];
- mmi.halfword[1] = ip->halfword[0];
- return ((mmi.mm_m_format.opcode == mm_pool32b_op &&
- mmi.mm_m_format.rd > 9 &&
- mmi.mm_m_format.base == 29 &&
- mmi.mm_m_format.func == mm_swm32_func) ||
- (mmi.i_format.opcode == mm_sw32_op &&
- mmi.i_format.rs == 29 &&
- mmi.i_format.rt == 31));
- }
+ return ((ip->mm16_r5_format.opcode == mm_swsp16_op &&
+ ip->mm16_r5_format.rt == 31) ||
+ (ip->mm16_m_format.opcode == mm_pool16c_op &&
+ ip->mm16_m_format.func == mm_swm16_op) ||
+ /* 32bit instruction */
+ (ip->mm_m_format.opcode == mm_pool32b_op &&
+ ip->mm_m_format.rd > 9 &&
+ ip->mm_m_format.base == 29 &&
+ ip->mm_m_format.func == mm_swm32_func) ||
+ (ip->i_format.opcode == mm_sw32_op &&
+ ip->i_format.rs == 29 && ip->i_format.rt == 31));
#else
/* sw / sd $ra, offset($sp) */
return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
@@ -265,16 +261,16 @@ static inline int is_jump_ins(union mips_instruction *ip)
*
* microMIPS is kind of more fun...
*/
- union mips_instruction mmi;
-
- mmi.word = (ip->halfword[0] << 16);
+ if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
+ (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op))
+ return 1;
- if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
- (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
- ip->j_format.opcode == mm_jal32_op)
+ if (ip->j_format.opcode == mm_jal32_op ||
+ ip->j_format.opcode == mm_j32_op)
return 1;
+
if (ip->r_format.opcode != mm_pool32a_op ||
- ip->r_format.func != mm_pool32axf_op)
+ ip->r_format.func != mm_pool32axf_op)
return 0;
return (((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op);
#else
@@ -299,17 +295,13 @@ static inline int is_sp_move_ins(union mips_instruction *ip)
*
* microMIPS is not more fun...
*/
- if (mm_insn_16bit(ip->halfword[0])) {
- union mips_instruction mmi;
-
- mmi.word = (ip->halfword[0] << 16);
- return ((mmi.mm16_r3_format.opcode == mm_pool16d_op &&
- mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
- (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
- mmi.mm16_r5_format.rt == 29));
- }
- return (ip->mm_i_format.opcode == mm_addiu32_op &&
- ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29);
+ return ((ip->mm16_r3_format.opcode == mm_pool16d_op &&
+ ip->mm16_r3_format.simmediate && mm_addiusp_func) ||
+ (ip->mm16_r5_format.opcode == mm_pool16d_op &&
+ ip->mm16_r5_format.rt == 29) ||
+ /* 32bit instruction */
+ (ip->mm_i_format.opcode == mm_addiu32_op &&
+ ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29));
#else
/* addiu/daddiu sp,sp,-imm */
if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
@@ -320,15 +312,76 @@ static inline int is_sp_move_ins(union mips_instruction *ip)
return 0;
}
-static int get_frame_info(struct mips_frame_info *info)
-{
#ifdef CONFIG_CPU_MICROMIPS
- union mips_instruction *ip = (void *) (((char *) info->func) - 1);
+/*
+ * A few fun facts on MIPS16
+ *
+ * 1. MIPS16 instructions are either 16-bit or 32-bit in length
+ * 2. MIPS16 32-bit instruction may not be on word boundary
+ * 3. MIPS16 instructions are placed in 32-bit memory element,
+ * in endian-dependent order.
+ *
+ * Big Endian
+ * +---------------+---------------+
+ * | ip1 | ip2 |
+ * +---------------+---------------+
+ *
+ * Little Endian
+ * +---------------+---------------+
+ * | ip2 | ip1 |
+ * +---------------+---------------+
+ *
+ * fetch_instruction and MIPS16_fetch_halfword do the followings:
+ *
+ * 1. fetch word from word-aligned address
+ * 2. access the fetched word using halfword (defeat endian issue)
+ * 3. assemble 16/32 bit MIPS16 instruction from halfword(s)
+ */
+static inline void MIPS16_fetch_halfword(union mips_instruction **ip,
+ unsigned short *this_halfword,
+ unsigned short *prev_halfword)
+{
+ if (*prev_halfword) {
+ *this_halfword = *prev_halfword;
+ *prev_halfword = 0;
+ } else {
+ /* advance pointer to next word */
+ *this_halfword = (*ip)->halfword[0];
+ *prev_halfword = (*ip)->halfword[1];
+ *ip += 1;
+ }
+}
+
+static inline void fetch_instruction(union mips_instruction **ip,
+ union mips_instruction *mi,
+ unsigned short *prev_halfword)
+{
+ /* fetch the first MIPS16 instruction */
+ MIPS16_fetch_halfword(ip, &mi->halfword[0], prev_halfword);
+
+ /* fetch the second half if it is a 32bit one */
+ if (mm_insn_16bit(mi->halfword[0]))
+ mi->halfword[1] = 0;
+ else
+ MIPS16_fetch_halfword(ip, &mi->halfword[1], prev_halfword);
+}
#else
- union mips_instruction *ip = info->func;
+static inline void fetch_instruction(union mips_instruction **ip,
+ union mips_instruction *mi,
+ unsigned short *halfword)
+{
+ /* do simple assignment for mips32 mode */
+ *mi = **ip;
+ *ip += 1;
+}
#endif
+
+static int get_frame_info(struct mips_frame_info *info)
+{
+ union mips_instruction *ip = info->func;
+ union mips_instruction inst, *max_ip;
unsigned max_insns = info->func_size / sizeof(union mips_instruction);
- unsigned i;
+ unsigned short halfword = 0;
info->pc_offset = -1;
info->frame_size = 0;
@@ -340,37 +393,38 @@ static int get_frame_info(struct mips_frame_info *info)
max_insns = 128U; /* unknown function size */
max_insns = min(128U, max_insns);
- for (i = 0; i < max_insns; i++, ip++) {
+#ifdef CONFIG_CPU_MICROMIPS
+ /* align start address to word boundary, lose mode bit. */
+ ip = (union mips_instruction *)((unsigned long)ip & ~0x3);
+#endif
+ max_ip = ip + max_insns * sizeof(union mips_instruction);
+
+ while (ip < max_ip) {
+ fetch_instruction(&ip, &inst, &halfword);
- if (is_jump_ins(ip))
+ if (is_jump_ins(&inst))
break;
if (!info->frame_size) {
- if (is_sp_move_ins(ip))
- {
+ if (!is_sp_move_ins(&inst))
+ continue;
#ifdef CONFIG_CPU_MICROMIPS
- if (mm_insn_16bit(ip->halfword[0]))
- {
- unsigned short tmp;
-
- if (ip->halfword[0] & mm_addiusp_func)
- {
- tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
- info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
- } else {
- tmp = (ip->halfword[0] >> 1);
- info->frame_size = -(signed short)(tmp & 0xf);
- }
- ip = (void *) &ip->halfword[1];
- ip--;
- } else
+ if (mm_insn_16bit(inst.halfword[0])) {
+ unsigned short tmp;
+
+ if (inst.halfword[0] & mm_addiusp_func) {
+ tmp = (((inst.halfword[0] >> 1) & 0x1ff) << 2);
+ info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
+ } else {
+ tmp = (inst.halfword[0] >> 1);
+ info->frame_size = -(signed short)(tmp & 0xf);
+ }
+ } else
#endif
- info->frame_size = - ip->i_format.simmediate;
- }
- continue;
+ info->frame_size = - inst.i_format.simmediate;
}
- if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
+ if (info->pc_offset == -1 && is_ra_save_ins(&inst)) {
info->pc_offset =
- ip->i_format.simmediate / sizeof(long);
+ inst.i_format.simmediate / sizeof(long);
break;
}
}
@@ -390,20 +444,34 @@ static unsigned long get___schedule_addr(void)
{
return kallsyms_lookup_name("__schedule");
}
-#else
+#else /* CONFIG_KALLSYMS */
static unsigned long get___schedule_addr(void)
{
union mips_instruction *ip = (void *)schedule;
+ union mips_instruction inst;
+ union mips_instruction *max_ip;
int max_insns = 8;
- int i;
+ unsigned short halfword;
+
+#ifdef CONFIG_CPU_MICROMIPS
+ /* align start address to word boundary, lose mode bit */
+ ip = (union mips_instruction *)((unsigned long)ip & ~0x3);
+#endif
+ max_ip = ip + max_insns * sizeof(union mips_instruction);
- for (i = 0; i < max_insns; i++, ip++) {
- if (ip->j_format.opcode == j_op)
- return J_TARGET(ip, ip->j_format.target);
+ while (ip < max_ip) {
+ fetch_instruction(&ip, &inst, &halfword);
+#ifdef CONFIG_CPU_MICROMIPS
+ if (inst.j_format.opcode == mm_j32_op)
+ return J_TARGET(ip+1, inst.j_format.target);
+#else
+ if (inst.j_format.opcode == j_op)
+ return J_TARGET(ip, inst.j_format.target);
+#endif
}
return 0;
}
-#endif
+#endif /* !CONFIG_KALLSYMS */
static int __init frame_info_init(void)
{
--
1.7.10.2 (Apple Git-33)
