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Diffstat (limited to 'arch/arm/kernel/unwind.c')
-rw-r--r--arch/arm/kernel/unwind.c102
1 files changed, 86 insertions, 16 deletions
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 59fdf257bf8b..f60547dadc93 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -28,11 +28,14 @@
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/list.h>
+#include <linux/module.h>
#include <asm/stacktrace.h>
#include <asm/traps.h>
#include <asm/unwind.h>
+#include "reboot.h"
+
/* Dummy functions to avoid linker complaints */
void __aeabi_unwind_cpp_pr0(void)
{
@@ -53,6 +56,7 @@ struct unwind_ctrl_block {
unsigned long vrs[16]; /* virtual register set */
const unsigned long *insn; /* pointer to the current instructions word */
unsigned long sp_high; /* highest value of sp allowed */
+ unsigned long *lr_addr; /* address of LR value on the stack */
/*
* 1 : check for stack overflow for each register pop.
* 0 : save overhead if there is plenty of stack remaining.
@@ -237,6 +241,8 @@ static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
* from being tracked by KASAN.
*/
ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
+ if (reg == 14)
+ ctrl->lr_addr = *vsp;
(*vsp)++;
return URC_OK;
}
@@ -256,8 +262,9 @@ static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
mask >>= 1;
reg++;
}
- if (!load_sp)
+ if (!load_sp) {
ctrl->vrs[SP] = (unsigned long)vsp;
+ }
return URC_OK;
}
@@ -301,6 +308,29 @@ static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
return URC_OK;
}
+static unsigned long unwind_decode_uleb128(struct unwind_ctrl_block *ctrl)
+{
+ unsigned long bytes = 0;
+ unsigned long insn;
+ unsigned long result = 0;
+
+ /*
+ * unwind_get_byte() will advance `ctrl` one instruction at a time, so
+ * loop until we get an instruction byte where bit 7 is not set.
+ *
+ * Note: This decodes a maximum of 4 bytes to output 28 bits data where
+ * max is 0xfffffff: that will cover a vsp increment of 1073742336, hence
+ * it is sufficient for unwinding the stack.
+ */
+ do {
+ insn = unwind_get_byte(ctrl);
+ result |= (insn & 0x7f) << (bytes * 7);
+ bytes++;
+ } while (!!(insn & 0x80) && (bytes != sizeof(result)));
+
+ return result;
+}
+
/*
* Execute the current unwind instruction.
*/
@@ -313,9 +343,9 @@ static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
if ((insn & 0xc0) == 0x00)
ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
- else if ((insn & 0xc0) == 0x40)
+ else if ((insn & 0xc0) == 0x40) {
ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
- else if ((insn & 0xf0) == 0x80) {
+ } else if ((insn & 0xf0) == 0x80) {
unsigned long mask;
insn = (insn << 8) | unwind_get_byte(ctrl);
@@ -330,9 +360,9 @@ static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
if (ret)
goto error;
} else if ((insn & 0xf0) == 0x90 &&
- (insn & 0x0d) != 0x0d)
+ (insn & 0x0d) != 0x0d) {
ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
- else if ((insn & 0xf0) == 0xa0) {
+ } else if ((insn & 0xf0) == 0xa0) {
ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
if (ret)
goto error;
@@ -354,7 +384,7 @@ static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
if (ret)
goto error;
} else if (insn == 0xb2) {
- unsigned long uleb128 = unwind_get_byte(ctrl);
+ unsigned long uleb128 = unwind_decode_uleb128(ctrl);
ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
} else {
@@ -375,23 +405,32 @@ error:
*/
int unwind_frame(struct stackframe *frame)
{
- unsigned long low;
const struct unwind_idx *idx;
struct unwind_ctrl_block ctrl;
+ unsigned long sp_low;
/* store the highest address on the stack to avoid crossing it*/
- low = frame->sp;
- ctrl.sp_high = ALIGN(low, THREAD_SIZE);
+ sp_low = frame->sp;
+ ctrl.sp_high = ALIGN(sp_low - THREAD_SIZE, THREAD_ALIGN)
+ + THREAD_SIZE;
pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
frame->pc, frame->lr, frame->sp);
- if (!kernel_text_address(frame->pc))
- return -URC_FAILURE;
-
idx = unwind_find_idx(frame->pc);
if (!idx) {
- pr_warn("unwind: Index not found %08lx\n", frame->pc);
+ if (frame->pc && kernel_text_address(frame->pc)) {
+ if (in_module_plt(frame->pc) && frame->pc != frame->lr) {
+ /*
+ * Quoting Ard: Veneers only set PC using a
+ * PC+immediate LDR, and so they don't affect
+ * the state of the stack or the register file
+ */
+ frame->pc = frame->lr;
+ return URC_OK;
+ }
+ pr_warn("unwind: Index not found %08lx\n", frame->pc);
+ }
return -URC_FAILURE;
}
@@ -403,7 +442,20 @@ int unwind_frame(struct stackframe *frame)
if (idx->insn == 1)
/* can't unwind */
return -URC_FAILURE;
- else if ((idx->insn & 0x80000000) == 0)
+ else if (frame->pc == prel31_to_addr(&idx->addr_offset)) {
+ /*
+ * Unwinding is tricky when we're halfway through the prologue,
+ * since the stack frame that the unwinder expects may not be
+ * fully set up yet. However, one thing we do know for sure is
+ * that if we are unwinding from the very first instruction of
+ * a function, we are still effectively in the stack frame of
+ * the caller, and the unwind info has no relevance yet.
+ */
+ if (frame->pc == frame->lr)
+ return -URC_FAILURE;
+ frame->pc = frame->lr;
+ return URC_OK;
+ } else if ((idx->insn & 0x80000000) == 0)
/* prel31 to the unwind table */
ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
else if ((idx->insn & 0xff000000) == 0x80000000)
@@ -430,6 +482,16 @@ int unwind_frame(struct stackframe *frame)
ctrl.check_each_pop = 0;
+ if (prel31_to_addr(&idx->addr_offset) == (u32)&call_with_stack) {
+ /*
+ * call_with_stack() is the only place where we permit SP to
+ * jump from one stack to another, and since we know it is
+ * guaranteed to happen, set up the SP bounds accordingly.
+ */
+ sp_low = frame->fp;
+ ctrl.sp_high = ALIGN(frame->fp, THREAD_SIZE);
+ }
+
while (ctrl.entries > 0) {
int urc;
if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
@@ -437,7 +499,7 @@ int unwind_frame(struct stackframe *frame)
urc = unwind_exec_insn(&ctrl);
if (urc < 0)
return urc;
- if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high)
+ if (ctrl.vrs[SP] < sp_low || ctrl.vrs[SP] > ctrl.sp_high)
return -URC_FAILURE;
}
@@ -452,6 +514,7 @@ int unwind_frame(struct stackframe *frame)
frame->sp = ctrl.vrs[SP];
frame->lr = ctrl.vrs[LR];
frame->pc = ctrl.vrs[PC];
+ frame->lr_addr = ctrl.lr_addr;
return URC_OK;
}
@@ -461,6 +524,8 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
{
struct stackframe frame;
+ printk("%sCall trace: ", loglvl);
+
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
@@ -475,7 +540,12 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;
frame.lr = (unsigned long)__builtin_return_address(0);
- frame.pc = (unsigned long)unwind_backtrace;
+ /* We are saving the stack and execution state at this
+ * point, so we should ensure that frame.pc is within
+ * this block of code.
+ */
+here:
+ frame.pc = (unsigned long)&&here;
} else {
/* task blocked in __switch_to */
frame.fp = thread_saved_fp(tsk);
generated by cgit (git 2.34.1) at 2025-12-24 17:43:35 +0000