Messages in this thread | | | Subject | Re: [PATCH v4 10/21] perf arm_spe: Fixup top byte for data virtual address | From | André Przywara <> | Date | Tue, 27 Oct 2020 15:01:26 +0000 |
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On 27/10/2020 03:09, Leo Yan wrote: > To establish a valid address from the address packet payload and finally > the address value can be used for parsing data symbol in DSO, current > code uses 0xff to replace the tag in the top byte of data virtual > address. > > So far the code only fixups top byte for the memory layouts with 4KB > pages, it misses to support memory layouts with 64KB pages. > > This patch adds the conditions for checking bits [55:48] are 0xf0 or > 0xfd, if detects the patterns it will fill 0xff into the top byte of the > address, also adds comment to explain the fixing up. > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > --- > .../util/arm-spe-decoder/arm-spe-decoder.c | 24 ++++++++++++++++--- > 1 file changed, 21 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c > index 776b3e6628bb..e135ac01d94a 100644 > --- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c > @@ -24,7 +24,7 @@ > > static u64 arm_spe_calc_ip(int index, u64 payload) > { > - u64 ns, el; > + u64 ns, el, val; > > /* Instruction virtual address or Branch target address */ > if (index == SPE_ADDR_PKT_HDR_INDEX_INS || > @@ -45,8 +45,26 @@ static u64 arm_spe_calc_ip(int index, u64 payload) > /* Clean tags */ > payload = SPE_ADDR_PKT_ADDR_GET_BYTES_0_6(payload); > > - /* Fill highest byte if bits [48..55] is 0xff */ > - if (SPE_ADDR_PKT_ADDR_GET_BYTE_6(payload) == 0xffULL) > + /* > + * Armv8 ARM (ARM DDI 0487F.c), chapter "D10.2.1 Address packet" > + * defines the data virtual address payload format, the top byte > + * (bits [63:56]) is assigned as top-byte tag; so we only can > + * retrieve address value from bits [55:0]. > + * > + * According to Documentation/arm64/memory.rst, if detects the > + * specific pattern in bits [55:48] of payload which falls in > + * the kernel space, should fixup the top byte and this allows > + * perf tool to parse DSO symbol for data address correctly. > + * > + * For this reason, if detects the bits [55:48] is one of > + * following values, will fill 0xff into the top byte: > + * > + * - 0xff (for most kernel memory regions); > + * - 0xf0 (for kernel logical memory map with 64KB pages); > + * - 0xfd (for kasan shadow region with 64KB pages). > + */ > + val = SPE_ADDR_PKT_ADDR_GET_BYTE_6(payload); > + if (val == 0xffULL || val == 0xf0ULL || val == 0xfdULL)
But those values are just the beginning of the region used by the kernel, aren't they? So the kernel logical map goes from 0xfff000.. to 0xfff7fff..., for instance.
But actually I wonder why were are so selective here? Wouldn't it just suffice to look at bits [55:52] to be either 0 or F?
Cheers, Andre
> payload |= 0xffULL << SPE_ADDR_PKT_ADDR_BYTE7_SHIFT; > > /* Data access physical address */ >
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