summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/kernel/ftrace.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/powerpc/kernel/ftrace.c')
-rw-r--r--arch/powerpc/kernel/ftrace.c171
1 files changed, 55 insertions, 116 deletions
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 6a014c763cc..d178834fe50 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -10,6 +10,8 @@
*
*/
+#define pr_fmt(fmt) "ftrace-powerpc: " fmt
+
#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
@@ -105,11 +107,9 @@ __ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op;
- unsigned int jmp[5];
- unsigned long ptr;
+ unsigned long entry, ptr;
unsigned long ip = rec->ip;
- unsigned long tramp;
- int offset;
+ void *tramp;
/* read where this goes */
if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
@@ -117,101 +117,46 @@ __ftrace_make_nop(struct module *mod,
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
- printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
+ pr_err("Not expected bl: opcode is %x\n", op);
return -EINVAL;
}
/* lets find where the pointer goes */
- tramp = find_bl_target(ip, op);
-
- /*
- * On PPC64 the trampoline looks like:
- * 0x3d, 0x82, 0x00, 0x00, addis r12,r2, <high>
- * 0x39, 0x8c, 0x00, 0x00, addi r12,r12, <low>
- * Where the bytes 2,3,6 and 7 make up the 32bit offset
- * to the TOC that holds the pointer.
- * to jump to.
- * 0xf8, 0x41, 0x00, 0x28, std r2,40(r1)
- * 0xe9, 0x6c, 0x00, 0x20, ld r11,32(r12)
- * The actually address is 32 bytes from the offset
- * into the TOC.
- * 0xe8, 0x4c, 0x00, 0x28, ld r2,40(r12)
- */
-
- pr_devel("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
-
- /* Find where the trampoline jumps to */
- if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
- printk(KERN_ERR "Failed to read %lx\n", tramp);
- return -EFAULT;
- }
+ tramp = (void *)find_bl_target(ip, op);
- pr_devel(" %08x %08x", jmp[0], jmp[1]);
+ pr_devel("ip:%lx jumps to %p", ip, tramp);
- /* verify that this is what we expect it to be */
- if (((jmp[0] & 0xffff0000) != 0x3d820000) ||
- ((jmp[1] & 0xffff0000) != 0x398c0000) ||
- (jmp[2] != 0xf8410028) ||
- (jmp[3] != 0xe96c0020) ||
- (jmp[4] != 0xe84c0028)) {
- printk(KERN_ERR "Not a trampoline\n");
+ if (!is_module_trampoline(tramp)) {
+ pr_err("Not a trampoline\n");
return -EINVAL;
}
- /* The bottom half is signed extended */
- offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
- (int)((short)jmp[1]);
-
- pr_devel(" %x ", offset);
-
- /* get the address this jumps too */
- tramp = mod->arch.toc + offset + 32;
- pr_devel("toc: %lx", tramp);
-
- if (probe_kernel_read(jmp, (void *)tramp, 8)) {
- printk(KERN_ERR "Failed to read %lx\n", tramp);
+ if (module_trampoline_target(mod, tramp, &ptr)) {
+ pr_err("Failed to get trampoline target\n");
return -EFAULT;
}
- pr_devel(" %08x %08x\n", jmp[0], jmp[1]);
-
-#ifdef __LITTLE_ENDIAN__
- ptr = ((unsigned long)jmp[1] << 32) + jmp[0];
-#else
- ptr = ((unsigned long)jmp[0] << 32) + jmp[1];
-#endif
+ pr_devel("trampoline target %lx", ptr);
+ entry = ppc_global_function_entry((void *)addr);
/* This should match what was called */
- if (ptr != ppc_function_entry((void *)addr)) {
- printk(KERN_ERR "addr does not match %lx\n", ptr);
- return -EINVAL;
- }
-
- /*
- * We want to nop the line, but the next line is
- * 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1)
- * This needs to be turned to a nop too.
- */
- if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
- return -EFAULT;
-
- if (op != 0xe8410028) {
- printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
+ if (ptr != entry) {
+ pr_err("addr %lx does not match expected %lx\n", ptr, entry);
return -EINVAL;
}
/*
- * Milton Miller pointed out that we can not blindly do nops.
- * If a task was preempted when calling a trace function,
- * the nops will remove the way to restore the TOC in r2
- * and the r2 TOC will get corrupted.
- */
-
- /*
- * Replace:
- * bl <tramp> <==== will be replaced with "b 1f"
- * ld r2,40(r1)
- * 1:
+ * Our original call site looks like:
+ *
+ * bl <tramp>
+ * ld r2,XX(r1)
+ *
+ * Milton Miller pointed out that we can not simply nop the branch.
+ * If a task was preempted when calling a trace function, the nops
+ * will remove the way to restore the TOC in r2 and the r2 TOC will
+ * get corrupted.
+ *
+ * Use a b +8 to jump over the load.
*/
op = 0x48000008; /* b +8 */
@@ -236,7 +181,7 @@ __ftrace_make_nop(struct module *mod,
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
- printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
+ pr_err("Not expected bl: opcode is %x\n", op);
return -EINVAL;
}
@@ -255,7 +200,7 @@ __ftrace_make_nop(struct module *mod,
/* Find where the trampoline jumps to */
if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
- printk(KERN_ERR "Failed to read %lx\n", tramp);
+ pr_err("Failed to read %lx\n", tramp);
return -EFAULT;
}
@@ -266,7 +211,7 @@ __ftrace_make_nop(struct module *mod,
((jmp[1] & 0xffff0000) != 0x398c0000) ||
(jmp[2] != 0x7d8903a6) ||
(jmp[3] != 0x4e800420)) {
- printk(KERN_ERR "Not a trampoline\n");
+ pr_err("Not a trampoline\n");
return -EINVAL;
}
@@ -278,8 +223,7 @@ __ftrace_make_nop(struct module *mod,
pr_devel(" %lx ", tramp);
if (tramp != addr) {
- printk(KERN_ERR
- "Trampoline location %08lx does not match addr\n",
+ pr_err("Trampoline location %08lx does not match addr\n",
tramp);
return -EINVAL;
}
@@ -320,15 +264,13 @@ int ftrace_make_nop(struct module *mod,
*/
if (!rec->arch.mod) {
if (!mod) {
- printk(KERN_ERR "No module loaded addr=%lx\n",
- addr);
+ pr_err("No module loaded addr=%lx\n", addr);
return -EFAULT;
}
rec->arch.mod = mod;
} else if (mod) {
if (mod != rec->arch.mod) {
- printk(KERN_ERR
- "Record mod %p not equal to passed in mod %p\n",
+ pr_err("Record mod %p not equal to passed in mod %p\n",
rec->arch.mod, mod);
return -EINVAL;
}
@@ -349,45 +291,42 @@ static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op[2];
- unsigned long ip = rec->ip;
+ void *ip = (void *)rec->ip;
/* read where this goes */
- if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
+ if (probe_kernel_read(op, ip, sizeof(op)))
return -EFAULT;
/*
- * It should be pointing to two nops or
- * b +8; ld r2,40(r1)
+ * We expect to see:
+ *
+ * b +8
+ * ld r2,XX(r1)
+ *
+ * The load offset is different depending on the ABI. For simplicity
+ * just mask it out when doing the compare.
*/
- if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
- ((op[0] != PPC_INST_NOP) || (op[1] != PPC_INST_NOP))) {
- printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
+ if ((op[0] != 0x48000008) || ((op[1] & 0xffff0000) != 0xe8410000)) {
+ pr_err("Unexpected call sequence: %x %x\n", op[0], op[1]);
return -EINVAL;
}
/* If we never set up a trampoline to ftrace_caller, then bail */
if (!rec->arch.mod->arch.tramp) {
- printk(KERN_ERR "No ftrace trampoline\n");
+ pr_err("No ftrace trampoline\n");
return -EINVAL;
}
- /* create the branch to the trampoline */
- op[0] = create_branch((unsigned int *)ip,
- rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
- if (!op[0]) {
- printk(KERN_ERR "REL24 out of range!\n");
+ /* Ensure branch is within 24 bits */
+ if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+ pr_err("Branch out of range\n");
return -EINVAL;
}
- /* ld r2,40(r1) */
- op[1] = 0xe8410028;
-
- pr_devel("write to %lx\n", rec->ip);
-
- if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
- return -EPERM;
-
- flush_icache_range(ip, ip + 8);
+ if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+ pr_err("REL24 out of range!\n");
+ return -EINVAL;
+ }
return 0;
}
@@ -404,13 +343,13 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
/* It should be pointing to a nop */
if (op != PPC_INST_NOP) {
- printk(KERN_ERR "Expected NOP but have %x\n", op);
+ pr_err("Expected NOP but have %x\n", op);
return -EINVAL;
}
/* If we never set up a trampoline to ftrace_caller, then bail */
if (!rec->arch.mod->arch.tramp) {
- printk(KERN_ERR "No ftrace trampoline\n");
+ pr_err("No ftrace trampoline\n");
return -EINVAL;
}
@@ -418,7 +357,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
op = create_branch((unsigned int *)ip,
rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
if (!op) {
- printk(KERN_ERR "REL24 out of range!\n");
+ pr_err("REL24 out of range!\n");
return -EINVAL;
}
@@ -456,7 +395,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
* already have a module defined.
*/
if (!rec->arch.mod) {
- printk(KERN_ERR "No module loaded\n");
+ pr_err("No module loaded\n");
return -EINVAL;
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-04-03 07:25:43 +0000