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powerpc/ftrace: Add separate ftrace_init_nop() with additional validation

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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 <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/f373684081e8e98be09b7f44d2d93069768324dc.1687166935.git.naveen@kernel.org
This commit is contained in:
Naveen N Rao 2023-06-19 15:17:28 +05:30 committed by Michael Ellerman
parent 33bb8a0be9
commit cc93b92332
2 changed files with 77 additions and 0 deletions
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6
arch/powerpc/include/asm/ftrace.h
View File

@ -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;
};

71
arch/powerpc/kernel/trace/ftrace.c
View File

@ -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);