Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> Currently, we validate instructions around the ftrace location every
> time we have to enable/disable ftrace. Introduce ftrace_init_nop() to
> instead perform all the validation during ftrace initialization. This
> allows us to simply patch the necessary instructions during
> enabling/disabling ftrace.
>
> Signed-off-by: Naveen N Rao <nav...@kernel.org>
Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu>
> ---
> arch/powerpc/include/asm/ftrace.h | 6 +++
> arch/powerpc/kernel/trace/ftrace.c | 71 ++++++++++++++++++++++++++++++
> 2 files changed, 77 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/ftrace.h
> b/arch/powerpc/include/asm/ftrace.h
> index 702aaf2efa966c..ef9f0b97670d1c 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -29,11 +29,17 @@ static inline unsigned long ftrace_call_adjust(unsigned
> long addr)
> unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
> unsigned long sp);
>
> +struct module;
> +struct dyn_ftrace;
> struct dyn_arch_ftrace {
> struct module *mod;
> };
>
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> +#define ftrace_need_init_nop() (true)
> +int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> +#define ftrace_init_nop ftrace_init_nop
> +
> struct ftrace_regs {
> struct pt_regs regs;
> };
> diff --git a/arch/powerpc/kernel/trace/ftrace.c
> b/arch/powerpc/kernel/trace/ftrace.c
> index 278bf8e52b6e89..98bd099c428ee0 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -31,6 +31,16 @@
> #define NUM_FTRACE_TRAMPS 2
> static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
>
> +static ppc_inst_t ftrace_create_branch_inst(unsigned long ip, unsigned long
> addr, int link)
> +{
> + ppc_inst_t op;
> +
> + WARN_ON(!is_offset_in_branch_range(addr - ip));
> + create_branch(&op, (u32 *)ip, addr, link ? BRANCH_SET_LINK : 0);
> +
> + return op;
> +}
> +
> static ppc_inst_t
> ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
> {
> @@ -597,6 +607,67 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned
> long old_addr,
> }
> #endif
>
> +int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
> +{
> + unsigned long addr, ip = rec->ip;
> + ppc_inst_t old, new;
> + int ret = 0;
> +
> + /* Verify instructions surrounding the ftrace location */
> + if (IS_ENABLED(CONFIG_PPC32)) {
> + /* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */
> + ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
> + if (!ret)
> + ret = ftrace_validate_inst(ip - 4,
> ppc_inst(PPC_RAW_STW(_R0, _R1, 4)));
> + } else if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
> + /* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl
> _mcount' */
> + ret = ftrace_read_inst(ip - 4, &old);
> + if (!ret && !ppc_inst_equal(old, ppc_inst(PPC_RAW_MFLR(_R0)))) {
> + ret = ftrace_validate_inst(ip - 8,
> ppc_inst(PPC_RAW_MFLR(_R0)));
> + ret |= ftrace_validate_inst(ip - 4,
> ppc_inst(PPC_RAW_STD(_R0, _R1, 16)));
> + }
> + } else {
> + return -EINVAL;
> + }
> +
> + if (ret)
> + return ret;
> +
> + if (!core_kernel_text(ip)) {
> + if (!mod) {
> + pr_err("0x%lx: No module provided for non-kernel
> address\n", ip);
> + return -EFAULT;
> + }
> + rec->arch.mod = mod;
> + }
> +
> + /* Nop-out the ftrace location */
> + new = ppc_inst(PPC_RAW_NOP());
> + addr = MCOUNT_ADDR;
> + if (is_offset_in_branch_range(addr - ip)) {
> + /* Within range */
> + old = ftrace_create_branch_inst(ip, addr, 1);
> + ret = ftrace_modify_code(ip, old, new);
> + } else if (core_kernel_text(ip) || (IS_ENABLED(CONFIG_MODULES) && mod))
> {
> + /*
> + * We would be branching to a linker-generated stub, or to the
> module _mcount
> + * stub. Let's just confirm we have a 'bl' here.
> + */
> + ret = ftrace_read_inst(ip, &old);
> + if (ret)
> + return ret;
> + if (!is_bl_op(old)) {
> + pr_err("0x%lx: expected (bl) != found (%08lx)\n", ip,
> ppc_inst_as_ulong(old));
> + return -EINVAL;
> + }
> + ret = patch_instruction((u32 *)ip, new);
> + } else {
> + return -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> int ftrace_update_ftrace_func(ftrace_func_t func)
> {
> unsigned long ip = (unsigned long)(&ftrace_call);
