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a2a4d4a6a0
If the load access fault occures in a leaf function (with
CONFIG_FRAME_POINTER=y), when wrong stack trace will be displayed:
[<ffffffff804853c2>] regmap_mmio_read32le+0xe/0x1c
---[ end trace 0000000000000000 ]---
Registers dump:
ra 0xffffffff80485758 <regmap_mmio_read+36>
sp 0xffffffc80200b9a0
fp 0xffffffc80200b9b0
pc 0xffffffff804853ba <regmap_mmio_read32le+6>
Stack dump:
0xffffffc80200b9a0: 0xffffffc80200b9e0 0xffffffc80200b9e0
0xffffffc80200b9b0: 0xffffffff8116d7e8 0x0000000000000100
0xffffffc80200b9c0: 0xffffffd8055b9400 0xffffffd8055b9400
0xffffffc80200b9d0: 0xffffffc80200b9f0 0xffffffff8047c526
0xffffffc80200b9e0: 0xffffffc80200ba30 0xffffffff8047fe9a
The assembler dump of the function preambula:
add sp,sp,-16
sd s0,8(sp)
add s0,sp,16
In the fist stack frame, where ra is not stored on the stack we can
observe:
0(sp) 8(sp)
.---------------------------------------------.
sp->| frame->fp | frame->ra (saved fp) |
|---------------------------------------------|
fp->| .... | .... |
|---------------------------------------------|
| | |
and in the code check is performed:
if (regs && (regs->epc == pc) && (frame->fp & 0x7))
I see no reason to check frame->fp value at all, because it is can be
uninitialized value on the stack. A better way is to check frame->ra to
be an address on the stack. After the stacktrace shows as expect:
[<ffffffff804853c2>] regmap_mmio_read32le+0xe/0x1c
[<ffffffff80485758>] regmap_mmio_read+0x24/0x52
[<ffffffff8047c526>] _regmap_bus_reg_read+0x1a/0x22
[<ffffffff8047fe9a>] _regmap_read+0x5c/0xea
[<ffffffff80480376>] _regmap_update_bits+0x76/0xc0
...
---[ end trace 0000000000000000 ]---
As pointed by Samuel Holland it is incorrect to remove check of the stackframe
entirely.
Changes since v2 [2]:
- Add accidentally forgotten curly brace
Changes since v1 [1]:
- Instead of just dropping frame->fp check, replace it with validation of
frame->ra, which should be a stack address.
- Move frame pointer validation into the separate function.
[1] https://lore.kernel.org/linux-riscv/20240426072701.6463-1-dev.mbstr@gmail.com/
[2] https://lore.kernel.org/linux-riscv/20240521131314.48895-1-dev.mbstr@gmail.com/
Fixes:
|
||
|---|---|---|
| .. | ||
| boot | ||
| configs | ||
| crypto | ||
| errata | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mm | ||
| net | ||
| purgatory | ||
| tools | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.debug | ||
| Kconfig.errata | ||
| Kconfig.socs | ||
| Makefile | ||
| Makefile.postlink | ||