Re: [PATCH v1 13/22] powerpc/ftrace: Use PPC_RAW_xxx() macros instead of opencoding.
From: Christophe Leroy
Date: Thu May 05 2022 - 12:48:07 EST
Le 04/05/2022 à 14:39, Christophe Leroy a écrit :
Le 18/04/2022 à 09:38, Naveen N. Rao a écrit :
Christophe Leroy wrote:
PPC_RAW_xxx() macros are self explanatory and less error prone
than open coding.
Use them in ftrace.c
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
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 ?
I called it PPC_LI() and PPC_LI_MASK, similar to PPC_LO, PPC_HI etc ...
+
/* 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 ?
Looked at it in more details, looks like STK_GOT is an assembly only
symbol, and ppc_asm.h is dedicated to ASM allthough it has recently
leaked a bit into C.
So I propose to leave it as is and do the change in a followup patch.
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