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afc76b8b80
linux/arch/riscv/kernel
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Guo Ren afc76b8b80
riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT 
This patch changes the current detour mechanism of dynamic ftrace
which has been discussed during LPC 2020 RISCV-MC [1].

Before the patch, we used mcount for detour:
<funca>:
	addi sp,sp,-16
	sd   ra,8(sp)
	sd   s0,0(sp)
	addi s0,sp,16
	mv   a5,ra
	mv   a0,a5
	auipc ra,0x0 -> nop
	jalr  -296(ra) <_mcount@plt> ->nop
	...

After the patch, we use nop call site area for detour:
<funca>:
	nop -> REG_S ra, -SZREG(sp)
	nop -> auipc ra, 0x?
	nop -> jalr ?(ra)
	nop -> REG_L ra, -SZREG(sp)
	...

The mcount mechanism is mixed with gcc function prologue which is
not very clear. The patchable function entry just put 16 bytes nop
before the front of the function prologue which could be filled
with a separated detour mechanism.

[1] https://www.linuxplumbersconf.org/event/7/contributions/807/

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
2021-01-14 15:09:05 -08:00
..
vdso riscv: Explicitly specify the build id style in vDSO Makefile again 2020-11-25 09:44:14 -08:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
asm-offsets.c riscv: Fixed kernel test robot warning 2020-12-10 17:47:23 -08:00
cacheinfo.c riscv: Add cache information in AUX vector 2020-09-15 18:46:08 -07:00
cpu_ops_sbi.c RISC-V: Support cpu hotplug 2020-03-31 11:28:30 -07:00
cpu_ops_spinwait.c RISC-V: Add cpu_ops and modify default booting method 2020-03-31 11:25:56 -07:00
cpu_ops.c treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
cpu-hotplug.c RISC-V: Support cpu hotplug 2020-03-31 11:28:30 -07:00
cpu.c RISC-V: Rename and move plic_find_hart_id() to arch directory 2020-06-09 19:11:20 -07:00
cpufeature.c RISC-V: Add bitmap reprensenting ISA features common across CPUs 2020-05-04 14:08:59 -07:00
efi-header.S RISC-V: Add PE/COFF header for EFI stub 2020-10-02 14:31:16 -07:00
efi.c RISC-V: Add EFI runtime services 2020-10-02 14:31:28 -07:00
entry.S riscv: Cleanup unnecessary define in asm-offset.c 2020-07-30 11:37:44 -07:00
fpu.S riscv: abstract out CSR names for supervisor vs machine mode 2019-11-05 09:20:42 -08:00
ftrace.c riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT 2021-01-14 15:09:05 -08:00
head.h RISC-V: Move DT mapping outof fixmap 2020-10-02 14:30:57 -07:00
head.S RISC-V Patches for the 5.11 Merge Window, Part 1 2020-12-18 10:43:07 -08:00
image-vars.h RISC-V: Add PE/COFF header for EFI stub 2020-10-02 14:31:16 -07:00
irq.c RISC-V: Remove do_IRQ() function 2020-06-09 19:11:24 -07:00
jump_label.c riscv: Add jump-label implementation 2020-07-30 11:37:43 -07:00
kgdb.c riscv: Fix "no previous prototype" compile warning in kgdb.c file 2020-07-09 20:09:30 -07:00
Makefile riscv: Fixup patch_text panic in ftrace 2021-01-14 15:09:04 -08:00
mcount-dyn.S riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT 2021-01-14 15:09:05 -08:00
mcount.S RISC-V: remove the unused return_to_handler export 2018-10-22 17:38:12 -07:00
module-sections.c riscv: add missing header file includes 2019-10-28 00:46:01 -07:00
module.c riscv: Support R_RISCV_ADD64 and R_RISCV_SUB64 relocs 2020-07-30 11:37:41 -07:00
patch.c riscv: Fixup compile error BUILD_BUG_ON failed 2021-01-14 15:09:01 -08:00
perf_callchain.c riscv: Make stack walk callback consistent with generic code 2020-11-20 18:53:38 -08:00
perf_event.c riscv: perf_event: Make some funciton static 2020-05-11 13:48:19 -07:00
perf_regs.c perf/arch: Remove perf_sample_data::regs_user_copy 2020-11-09 18:12:34 +01:00
process.c sched/idle: Fix arch_cpu_idle() vs tracing 2020-11-24 16:47:35 +01:00
ptrace.c RISC-V: Implement ptrace regs and stack API 2021-01-14 15:09:01 -08:00
reset.c riscv: cleanup the default power off implementation 2019-11-13 13:22:52 -08:00
riscv_ksyms.c riscv: provide memmove implementation 2020-12-10 17:27:54 -08:00
sbi.c riscv: Cleanup sbi function stubs when RISCV_SBI disabled 2021-01-07 17:19:17 -08:00
setup.c riscv: Add machine name to kernel boot log and stack dump output 2021-01-14 15:08:59 -08:00
signal.c riscv: add support for TIF_NOTIFY_SIGNAL 2020-12-12 09:17:38 -07:00
smp.c RISC-V: Remove CLINT related code from timer and arch 2020-08-20 10:58:13 -07:00
smpboot.c riscv: Add numa support for riscv64 platform 2021-01-14 15:08:58 -08:00
soc.c riscv: Fix builtin DTB handling 2021-01-07 19:00:50 -08:00
stacktrace.c riscv: Enable ARCH_STACKWALK 2020-11-25 16:03:59 -08:00
sys_riscv.c RISC-V: Don't allow write+exec only page mapping request in mmap 2020-06-18 17:28:53 -07:00
syscall_table.c riscv: add missing header file includes 2019-10-28 00:46:01 -07:00
time.c riscv: use vDSO common flow to reduce the latency of the time-related functions 2020-06-10 19:47:16 -07:00
traps_misaligned.c riscv: Unaligned load/store handling for M_MODE 2020-04-03 10:45:33 -07:00
traps.c RISC-V: Setup exception vector early 2020-07-30 11:37:48 -07:00
vdso.c RISC-V Patches for the 5.8 Merge Window, Part 2 2020-06-11 12:55:20 -07:00
vmlinux.lds.S RISC-V: Move dynamic relocation section under __init 2020-11-25 16:05:29 -08:00