From: Gustavo Romero <gustavo.romero@linaro.org>
To: "Richard Henderson" <richard.henderson@linaro.org>,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
qemu-devel@nongnu.org, alex.bennee@linaro.org
Cc: peter.maydell@linaro.org
Subject: Re: [PATCH v3 4/4] tests/tcg/aarch64: Extend MTE gdbstub tests to system mode
Date: Thu, 29 Aug 2024 17:13:14 -0300 [thread overview]
Message-ID: <f5b66bb8-bf39-40f6-e641-64ddcfd6ac13@linaro.org> (raw)
In-Reply-To: <65e4c975-83f9-4d9b-a8aa-37d9543afac7@linaro.org>
Hi Richard,
On 8/28/24 9:43 PM, Richard Henderson wrote:
> On 8/28/24 04:01, Gustavo Romero wrote:
>> SECTIONS
>> {
>> - /* virt machine, RAM starts at 1gb */
>> + /* Skip first 1 GiB on virt machine: RAM starts at 1 GiB. */
>> . = (1 << 30);
>
> Better is to use
>
> MEMORY {
> RAM (rwx) : ORIGIN = 1 << 30, LENGTH = 16M
> }
>
> (or whatever minimum length seems reasonable).
>
> Since there is only one memory region, it will be used by default and no further markup is required.
>
>> + /* Align text to first 2 MiB. */
>> + . = ALIGN(0 * 2M);
>
> This is pointless, of course: ALIGN(0) does nothing.
>
>> @@ -19,12 +21,12 @@ SECTIONS
>> *(.bss)
>> }
>> /*
>> - * Align the MTE page to the next 2mb boundary (i.e., the third 2mb chunk
>> - * starting from 1gb) by setting the address for symbol 'mte_page', which is
>> - * used in boot.S to setup the PTE and in the mte.S test as the address that
>> - * the MTE instructions operate on.
>> + * Align the MTE page to the next 2 MiB boundary (i.e., the third 2 MiB
>> + * chunk starting from 1 GiB) by setting the address for symbol 'mte_page',
>> + * which is used in boot.S to setup the PTE and in the mte.S test as the
>> + * address that the MTE instructions operate on.
>> */
>> - mte_page = ALIGN(1 << 22);
>> + mte_page = ALIGN(2 * 2M);
>
> This does not do what you think it does.
> It aligns to the next 4M boundary, not the next 2M boundary.
I see now. This works because by chance ALIGN(2M) == ALIGN(4M).
So, using the 'M' suffix, I understand this is correct (and works):
(diff against the my patch)
index 46f1092522..823d47f7e7 100644
--- a/tests/tcg/aarch64/system/kernel.ld
+++ b/tests/tcg/aarch64/system/kernel.ld
@@ -11,7 +11,7 @@ SECTIONS
*(.rodata)
}
/* align r/w section to next 2mb */
- . = ALIGN(1 << 21);
+ . = ALIGN(2M);
.data : {
*(.data)
}
@@ -24,7 +24,7 @@ SECTIONS
* used in boot.S to setup the PTE and in the mte.S test as the address that
* the MTE instructions operate on.
*/
- mte_page = ALIGN(1 << 22);
+ mte_page = ALIGN(2M);
/DISCARD/ : {
*(.ARM.attributes)
}
1 .text 00001e60 0000000040001000 0000000040001000 00011000 2**12
4 .data 00012000 0000000040200000 0000000040200000 00020000 2**12
0000000040400000 g .data 0000000000000000 mte_page
I was not able to make the MEMORY command work. I tried:
index 46f1092522..dc39518a16 100644
--- a/tests/tcg/aarch64/system/kernel.ld
+++ b/tests/tcg/aarch64/system/kernel.ld
@@ -1,9 +1,13 @@
ENTRY(__start)
+MEMORY
+{
+ ram (rwx) : ORIGIN = 1 << 30, LENGTH = 16M
+}
+
SECTIONS
{
/* virt machine, RAM starts at 1gb */
- . = (1 << 30);
.text : {
*(.text)
}
@@ -11,7 +15,7 @@ SECTIONS
*(.rodata)
}
/* align r/w section to next 2mb */
- . = ALIGN(1 << 21);
+ . = ALIGN(2M);
.data : {
*(.data)
}
@@ -24,7 +28,7 @@ SECTIONS
* used in boot.S to setup the PTE and in the mte.S test as the address that
* the MTE instructions operate on.
*/
- mte_page = ALIGN(1 << 22);
+ mte_page = ((1 << 30) + 4M);
/DISCARD/ : {
*(.ARM.attributes)
}
But it didn't work because data section is placed in the wrong place:
1 .text 00001e60 0000000040001000 0000000040001000 00011000 2**12
4 .data 00012000 0000000040003000 0000000040003000 00013000 2**12
0000000040400000 g *ABS* 0000000000000000 mte_page
Do you know why?
I also had to use 'mte_page = ((1 << 30) + 4M);' for the mte_page symbol because
the current location (.) seems to reset to zero for the sections, hence if I do:
+ mte_page = ALIGN(2M);
I get:
0000000040200000 g .data 0000000000000000 mte_page
Cheers,
Gustavo
next prev parent reply other threads:[~2024-08-29 20:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-25 14:52 [PATCH v3 0/4] gdbstub: Add support for MTE in system mode Gustavo Romero
2024-08-25 14:52 ` [PATCH v3 1/4] gdbstub: Use specific MMU index when probing MTE addresses Gustavo Romero
2024-08-25 14:52 ` [PATCH v3 2/4] gdbstub: Add support for MTE in system mode Gustavo Romero
2024-08-25 14:52 ` [PATCH v3 3/4] tests/guest-debug: Support passing arguments to the GDB test script Gustavo Romero
2024-09-06 13:49 ` Alex Bennée
2024-08-25 14:52 ` [PATCH v3 4/4] tests/tcg/aarch64: Extend MTE gdbstub tests to system mode Gustavo Romero
2024-08-26 6:10 ` Philippe Mathieu-Daudé
2024-08-27 12:42 ` Gustavo Romero
2024-08-27 18:01 ` Gustavo Romero
2024-08-29 0:43 ` Richard Henderson
2024-08-29 20:13 ` Gustavo Romero [this message]
2024-08-29 22:16 ` Richard Henderson
2024-08-30 22:35 ` Gustavo Romero
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