Messages in this thread | | | From | Haibo Li <> | Subject | Re: [PATCH v2] ARM:unwind:fix unwind abort for uleb128 case | Date | Fri, 14 Apr 2023 13:57:04 +0800 |
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> Il 13/04/23 09:34, Haibo Li ha scritto: > > 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> > > --- > > 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(-) > > > > diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c index > > 53be7ea6181b..f37e55fcf81d 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, > > + * we loop until we get an instruction byte where bit 7 is not set. > > + * Note:It decodes max 4 bytes to output 28bits data. > > + * 28bits data(0xfffffff) covers vsp increments of 1073742336. > > + * It is sufficent for unwinding stack. > > + */ > > /* > * 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. > */ Looks much better.Thanks. > > > + do { > > + insn = unwind_get_byte(ctrl); > > + result |= (insn & 0x7f) << (bytes * 7); > > + bytes++; > > also, I would do ... > > } while (!!(insn & 0x80) && bytes != sizeof(result)); > > ...compressing the code and not creating any human readability concern. > > after which, you can get my > > Reviewed-by: AngeloGioacchino Del Regno > <angelogioacchino.delregno@collabora.com> get it.I will make a new patch.
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