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powerpc/ftrace: Add module_trampoline_target() for PPC32

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module_trampoline_target() is used by __ftrace_modify_call().

Implement it for PPC32 so that CONFIG_DYNAMIC_FTRACE_WITH_REGS
can be activated on PPC32 as well.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/42345f464fb465f0fc76f3090e250be8fc1729f0.1635423081.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-10-28 14:24:03 +02:00 committed by Michael Ellerman
parent 88670fdb26
commit c93d4f6ecf
2 changed files with 29 additions and 33 deletions
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25
arch/powerpc/kernel/module_32.c
View File

@ -273,6 +273,31 @@ int apply_relocate_add(Elf32_Shdr *sechdrs,
} }
#ifdef CONFIG_DYNAMIC_FTRACE #ifdef CONFIG_DYNAMIC_FTRACE
int module_trampoline_target(struct module *mod, unsigned long addr,
unsigned long *target)
{
unsigned int jmp[4];
/* Find where the trampoline jumps to */
if (copy_from_kernel_nofault(jmp, (void *)addr, sizeof(jmp)))
return -EFAULT;
/* verify that this is what we expect it to be */
if ((jmp[0] & 0xffff0000) != PPC_RAW_LIS(_R12, 0) ||
(jmp[1] & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0) ||
jmp[2] != PPC_RAW_MTCTR(_R12) ||
jmp[3] != PPC_RAW_BCTR())
return -EINVAL;
addr = (jmp[1] & 0xffff) | ((jmp[0] & 0xffff) << 16);
if (addr & 0x8000)
addr -= 0x10000;
*target = addr;
return 0;
}
int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs) int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
{ {
module->arch.tramp = do_plt_call(module->core_layout.base, module->arch.tramp = do_plt_call(module->core_layout.base,

37
arch/powerpc/kernel/trace/ftrace.c
View File

@ -222,9 +222,8 @@ __ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr) struct dyn_ftrace *rec, unsigned long addr)
{ {
struct ppc_inst op; struct ppc_inst op;
unsigned int jmp[4];
unsigned long ip = rec->ip; unsigned long ip = rec->ip;
unsigned long tramp; unsigned long tramp, ptr;
if (copy_from_kernel_nofault(&op, (void *)ip, MCOUNT_INSN_SIZE)) if (copy_from_kernel_nofault(&op, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT; return -EFAULT;
@ -238,41 +237,13 @@ __ftrace_make_nop(struct module *mod,
/* lets find where the pointer goes */ /* lets find where the pointer goes */
tramp = find_bl_target(ip, op); tramp = find_bl_target(ip, op);
/*
* On PPC32 the trampoline looks like:
* 0x3d, 0x80, 0x00, 0x00 lis r12,sym@ha
* 0x39, 0x8c, 0x00, 0x00 addi r12,r12,sym@l
* 0x7d, 0x89, 0x03, 0xa6 mtctr r12
* 0x4e, 0x80, 0x04, 0x20 bctr
*/
pr_devel("ip:%lx jumps to %lx", ip, tramp);
/* Find where the trampoline jumps to */ /* Find where the trampoline jumps to */
if (copy_from_kernel_nofault(jmp, (void *)tramp, sizeof(jmp))) { if (module_trampoline_target(mod, tramp, &ptr)) {
pr_err("Failed to read %lx\n", tramp); pr_err("Failed to get trampoline target\n");
return -EFAULT; return -EFAULT;
} }
pr_devel(" %08x %08x ", jmp[0], jmp[1]); if (ptr != addr) {
/* verify that this is what we expect it to be */
if (((jmp[0] & 0xffff0000) != 0x3d800000) ||
((jmp[1] & 0xffff0000) != 0x398c0000) ||
(jmp[2] != 0x7d8903a6) ||
(jmp[3] != 0x4e800420)) {
pr_err("Not a trampoline\n");
return -EINVAL;
}
tramp = (jmp[1] & 0xffff) |
((jmp[0] & 0xffff) << 16);
if (tramp & 0x8000)
tramp -= 0x10000;
pr_devel(" %lx ", tramp);
if (tramp != addr) {
pr_err("Trampoline location %08lx does not match addr\n", pr_err("Trampoline location %08lx does not match addr\n",
tramp); tramp);
return -EINVAL; return -EINVAL;