| Message ID | 20230414061031.141430-1-haibo.li@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] ARM:unwind:fix unwind abort for uleb128 case | expand |
On Fri, Apr 14, 2023 at 8:10 AM Haibo Li <haibo.li@mediatek.com> wrote: > When unwind instruction is 0xb2,the subsequent instructions > are uleb128 bytes. > For now,it uses only the first uleb128 byte in code. > > For vsp increments of 0x204~0x400,use one uleb128 byte like below: > 0xc06a00e4 <unwind_test_work>: 0x80b27fac > Compact model index: 0 > 0xb2 0x7f vsp = vsp + 1024 > 0xac pop {r4, r5, r6, r7, r8, r14} > > For vsp increments larger than 0x400,use two uleb128 bytes like below: > 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c > Compact model index: 1 > 0xb2 0x81 0x01 vsp = vsp + 1032 > 0xac pop {r4, r5, r6, r7, r8, r14} > The unwind works well since the decoded uleb128 byte is also 0x81. > > For vsp increments larger than 0x600,use two uleb128 bytes like below: > 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c > Compact model index: 1 > 0xb2 0x81 0x02 vsp = vsp + 1544 > 0xac pop {r4, r5, r6, r7, r8, r14} > In this case,the decoded uleb128 result is 0x101(vsp=0x204+(0x101<<2)). > While the uleb128 used in code is 0x81(vsp=0x204+(0x81<<2)). > The unwind aborts at this frame since it gets incorrect vsp. > > To fix this,add uleb128 decode to cover all the above case. > > Signed-off-by: Haibo Li <haibo.li@mediatek.com> Way to go, remember to collect all the Reviewed-by tags before you put the patch into Russell's patch tracker. Yours, Linus Walleij
> On Fri, Apr 14, 2023 at 8:10 AM Haibo Li <haibo.li@mediatek.com> wrote: > > > When unwind instruction is 0xb2,the subsequent instructions are > > uleb128 bytes. > > For now,it uses only the first uleb128 byte in code. > > > > For vsp increments of 0x204~0x400,use one uleb128 byte like below: > > 0xc06a00e4 <unwind_test_work>: 0x80b27fac > > Compact model index: 0 > > 0xb2 0x7f vsp = vsp + 1024 > > 0xac pop {r4, r5, r6, r7, r8, r14} > > > > For vsp increments larger than 0x400,use two uleb128 bytes like below: > > 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c > > Compact model index: 1 > > 0xb2 0x81 0x01 vsp = vsp + 1032 > > 0xac pop {r4, r5, r6, r7, r8, r14} > > The unwind works well since the decoded uleb128 byte is also 0x81. > > > > For vsp increments larger than 0x600,use two uleb128 bytes like below: > > 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c > > Compact model index: 1 > > 0xb2 0x81 0x02 vsp = vsp + 1544 > > 0xac pop {r4, r5, r6, r7, r8, r14} > > In this case,the decoded uleb128 result is 0x101(vsp=0x204+(0x101<<2)). > > While the uleb128 used in code is 0x81(vsp=0x204+(0x81<<2)). > > The unwind aborts at this frame since it gets incorrect vsp. > > > > To fix this,add uleb128 decode to cover all the above case. > > > > Signed-off-by: Haibo Li <haibo.li@mediatek.com> > > Way to go, remember to collect all the Reviewed-by tags before you put the > patch into Russell's patch tracker. > > Yours, > Linus Walleij Thanks for reminding.I put the patch into Russell's patch tracker just now, together with the three Reviewed-by tags from you, Alexandre Mergnat and AngeloGioacchino Del Regno. Thank you all.
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c index 53be7ea6181b..9d2192156087 100644 --- a/arch/arm/kernel/unwind.c +++ b/arch/arm/kernel/unwind.c @@ -308,6 +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. */ @@ -361,7 +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 {
When unwind instruction is 0xb2,the subsequent instructions are uleb128 bytes. For now,it uses only the first uleb128 byte in code. For vsp increments of 0x204~0x400,use one uleb128 byte like below: 0xc06a00e4 <unwind_test_work>: 0x80b27fac Compact model index: 0 0xb2 0x7f vsp = vsp + 1024 0xac pop {r4, r5, r6, r7, r8, r14} For vsp increments larger than 0x400,use two uleb128 bytes like below: 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c Compact model index: 1 0xb2 0x81 0x01 vsp = vsp + 1032 0xac pop {r4, r5, r6, r7, r8, r14} The unwind works well since the decoded uleb128 byte is also 0x81. For vsp increments larger than 0x600,use two uleb128 bytes like below: 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c Compact model index: 1 0xb2 0x81 0x02 vsp = vsp + 1544 0xac pop {r4, r5, r6, r7, r8, r14} In this case,the decoded uleb128 result is 0x101(vsp=0x204+(0x101<<2)). While the uleb128 used in code is 0x81(vsp=0x204+(0x81<<2)). The unwind aborts at this frame since it gets incorrect vsp. To fix this,add uleb128 decode to cover all the above case. Signed-off-by: Haibo Li <haibo.li@mediatek.com> --- v3: -As AngeloGioacchino Del Regno suggested,improve the comment and compress the code v2: - As Linus Walleij and Alexandre Mergnat suggested,add comments for unwind_decode_uleb128 - As Alexandre Mergnat suggested,change variables declaration in Alphabetical order --- arch/arm/kernel/unwind.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-)