Re: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation
From: Sathvika Vasireddy
Date: Tue May 24 2022 - 07:00:41 EST
On 24/05/22 15:05, Christophe Leroy wrote:
Le 23/05/2022 à 19:55, Sathvika Vasireddy a écrit :
This patch enables objtool --mcount on powerpc, and
adds implementation specific to powerpc.
Signed-off-by: Sathvika Vasireddy <sv@xxxxxxxxxxxxx>
---
arch/powerpc/Kconfig | 1 +
tools/objtool/arch/powerpc/decode.c | 14 ++++++++++++++
tools/objtool/check.c | 12 +++++++-----
tools/objtool/elf.c | 13 +++++++++++++
tools/objtool/include/objtool/elf.h | 1 +
5 files changed, 36 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 732a3f91ee5e..3373d44a1298 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -233,6 +233,7 @@ config PPC
select HAVE_NMI if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
select HAVE_OPTPROBES
select HAVE_OBJTOOL if PPC64
+ select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
select HAVE_PERF_EVENTS
select HAVE_PERF_EVENTS_NMI if PPC64
select HAVE_PERF_REGS
diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index e3b77a6ce357..ad3d79fffac2 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -40,12 +40,26 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
struct list_head *ops_list)
{
u32 insn;
+ unsigned int opcode;
*immediate = 0;
memcpy(&insn, sec->data->d_buf+offset, 4);
*len = 4;
*type = INSN_OTHER;
+ opcode = (insn >> 26);
You dont need the brackets here.
+
+ switch (opcode) {
+ case 18: /* bl */
+ if ((insn & 3) == 1) {
+ *type = INSN_CALL;
+ *immediate = insn & 0x3fffffc;
+ if (*immediate & 0x2000000)
+ *immediate -= 0x4000000;
+ }
+ break;
+ }
+
return 0;
}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 056302d58e23..fd8bad092f89 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -832,7 +832,7 @@ static int create_mcount_loc_sections(struct objtool_file *file)
if (elf_add_reloc_to_insn(file->elf, sec,
idx * sizeof(unsigned long),
- R_X86_64_64,
+ elf_reloc_type_long(file->elf),
insn->sec, insn->offset))
return -1;
@@ -2183,7 +2183,7 @@ static int classify_symbols(struct objtool_file *file)
if (arch_is_retpoline(func))
func->retpoline_thunk = true;
- if (!strcmp(func->name, "__fentry__"))
+ if ((!strcmp(func->name, "__fentry__")) || (!strcmp(func->name, "_mcount")))
func->fentry = true;
if (is_profiling_func(func->name))
@@ -2259,9 +2259,11 @@ static int decode_sections(struct objtool_file *file)
* Must be before add_jump_destinations(), which depends on 'func'
* being set for alternatives, to enable proper sibling call detection.
*/
- ret = add_special_section_alts(file);
- if (ret)
- return ret;
+ if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
+ ret = add_special_section_alts(file);
+ if (ret)
+ return ret;
+ }
I think this change should be a patch by itself, it's not related to
powerpc.
Makes sense. I'll make this a separate patch in the next revision.
ret = add_jump_destinations(file);
if (ret)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c25e957c1e52..95763060d551 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -793,6 +793,19 @@ elf_create_section_symbol(struct elf *elf, struct section *sec)
return sym;
}
+int elf_reloc_type_long(struct elf *elf)
Not sure it's a good name, because for 32 bits we have to use 'int'.
Sure, I'll rename it to elf_reloc_type() or some such.
+{
+ switch (elf->ehdr.e_machine) {
+ case EM_X86_64:
+ return R_X86_64_64;
+ case EM_PPC64:
+ return R_PPC64_ADDR64;
+ default:
+ WARN("unknown machine...");
+ exit(-1);
+ }
+}
Wouldn't it be better to make that function arch specific ?
This is so that we can support cross architecture builds.
Thanks for reviewing!
- Sathvika