Le 18/04/2022 à 09:38, Naveen N. Rao a écrit :

Christophe Leroy wrote:

quoted

PPC_RAW_xxx() macros are self explanatory and less error prone
than open coding.

Use them in ftrace.c

Signed-off-by: Christophe Leroy <redacted>
---
 arch/powerpc/include/asm/ppc-opcode.h |  3 +++
 arch/powerpc/kernel/trace/ftrace.c    | 32 +++++++++------------------
 2 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc-opcode.h 

b/arch/powerpc/include/asm/ppc-opcode.h
index 82f1f0041c6f..281754aca0a3 100644

--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h

@@ -294,6 +294,8 @@

 #define PPC_INST_BL            0x48000001
 #define PPC_INST_BRANCH_COND        0x40800000

+#define PPC_INST_OFFSET24_MASK        0x03fffffc

This corresponds to the LI field, per the ISA. See section 8.1.2/1.7: 
'Instruction Fields'. Would it be better to name it PPC_INST_LI_MASK?

Isn't there a risk of confusing with the 'li' instruction ? Like we 
could have PPC_INST_LI just like we have PPC_INST_ADD ?

quoted

+
 /* Prefixes */
 #define PPC_INST_LFS            0xc0000000
 #define PPC_INST_STFS            0xd0000000

@@ -572,6 +574,7 @@

 #define PPC_RAW_EIEIO()            (0x7c0006ac)

 #define PPC_RAW_BRANCH(addr)        (PPC_INST_BRANCH | ((addr) & 
0x03fffffc))
+#define PPC_RAW_BL(offset)        (0x48000001 | ((offset) & 
PPC_INST_OFFSET24_MASK))

 /* Deal with instructions that older assemblers aren't aware of */
 #define    PPC_BCCTR_FLUSH        stringify_in_c(.long 
PPC_INST_BCCTR_FLUSH)

diff --git a/arch/powerpc/kernel/trace/ftrace.c 

b/arch/powerpc/kernel/trace/ftrace.c
index fdc0412c1d8a..afb1d12838c9 100644

--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c

@@ -90,19 +90,19 @@ static int test_24bit_addr(unsigned long ip, 

unsigned long addr)

 static int is_bl_op(ppc_inst_t op)
 {
-    return (ppc_inst_val(op) & 0xfc000003) == 0x48000001;
+    return (ppc_inst_val(op) & ~PPC_INST_OFFSET24_MASK) == 
PPC_RAW_BL(0);
 }

 static int is_b_op(ppc_inst_t op)
 {
-    return (ppc_inst_val(op) & 0xfc000003) == 0x48000000;
+    return (ppc_inst_val(op) & ~PPC_INST_OFFSET24_MASK) == 
PPC_RAW_BRANCH(0);
 }

 static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
 {
     int offset;

-    offset = (ppc_inst_val(op) & 0x03fffffc);
+    offset = (ppc_inst_val(op) & PPC_INST_OFFSET24_MASK);
     /* make it signed */
     if (offset & 0x02000000)
         offset |= 0xfe000000;

@@ -182,7 +182,7 @@ __ftrace_make_nop(struct module *mod,

      * Use a b +8 to jump over the load.
      */

-    pop = ppc_inst(PPC_INST_BRANCH | 8);    /* b +8 */
+    pop = ppc_inst(PPC_RAW_BRANCH(8));    /* b +8 */

     /*
      * Check what is in the next instruction. We can see ld 
r2,40(r1), but

@@ -394,17 +394,8 @@ int ftrace_make_nop(struct module *mod,

 static int
 expected_nop_sequence(void *ip, ppc_inst_t op0, ppc_inst_t op1)
 {
-    /*
-     * We expect to see:
-     *
-     * b +8
-     * ld r2,XX(r1)
-     *
-     * The load offset is different depending on the ABI. For simplicity
-     * just mask it out when doing the compare.
-     */
-    if (!ppc_inst_equal(op0, ppc_inst(0x48000008)) ||
-        (ppc_inst_val(op1) & 0xffff0000) != 0xe8410000)
+    if (!ppc_inst_equal(op0, ppc_inst(PPC_RAW_BRANCH(8))) ||
+        !ppc_inst_equal(op1, ppc_inst(PPC_INST_LD_TOC)))

It would be good to move PPC_INST_LD_TOC to ppc-opcode.h

It's not really just an instruction, it's closely linked to the ABI, so 
does it really belong to ppc-opcode.h ? Maybe it could be better to have 
it in ppc_asm.h instead, which already contains ABI related definitions ?

If we move it into ppc-opcode.h, then we also have to move 
R2_STACK_OFFSET. Or should we use STK_GOT defined in ppc_asm.h and drop 
R2_STACK_OFFSET ?

quoted

         return 0;
     return 1;
 }

@@ -412,7 +403,6 @@ expected_nop_sequence(void *ip, ppc_inst_t op0, 

ppc_inst_t op1)
 static int
 expected_nop_sequence(void *ip, ppc_inst_t op0, ppc_inst_t op1)
 {
-    /* look for patched "NOP" on ppc64 with -mprofile-kernel or ppc32 */
     if (!ppc_inst_equal(op0, ppc_inst(PPC_RAW_NOP())))
         return 0;
     return 1;

@@ -738,11 +728,11 @@ int __init ftrace_dyn_arch_init(void)

     int i;
     unsigned int *tramp[] = { ftrace_tramp_text, ftrace_tramp_init };
     u32 stub_insns[] = {
-        0xe98d0000 | PACATOC,    /* ld      r12,PACATOC(r13)    */
-        0x3d8c0000,        /* addis   r12,r12,<high>    */
-        0x398c0000,        /* addi    r12,r12,<low>    */
-        0x7d8903a6,        /* mtctr   r12            */
-        0x4e800420,        /* bctr                */
+        PPC_RAW_LD(_R12, _R13, PACATOC),
+        PPC_RAW_ADDIS(_R12, _R12, 0),
+        PPC_RAW_ADDIS(_R12, _R12, 0),

This should be PPC_RAW_ADDI.

Oops.

Christophe