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Re: [PATCH v2] coverage: place GCOV-generated .text.startup section in init text
- To: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 29 May 2026 11:41:50 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Timothy Pearson <tpearson@xxxxxxxxxxxxxxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- Delivery-date: Fri, 29 May 2026 10:42:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 29/05/2026 9:53 am, Dmytro Prokopchuk1 wrote:
> GCOV instrumentation can emit executable input sections such as
> .text.startup when CONFIG_COVERAGE is enabled.
>
> At present the x86 already places .text.startup in .init.text,
> but Arm, RISC-V and PPC do not. With CONFIG_COVERAGE=y .text.startup
> can therefore be treated as a linker orphan on those architectures.
>
> Constructors generated by coverage instrumentation can then point
> at code outside the normal RX text mapping, leading to early boot
> crashes from init_constructors():
>
> (XEN) [ 12.331193] Instruction Abort Trap. Syndrome=0xf
> (XEN) [ 12.334253] Walking Hypervisor VA 0xa00003ce000 on CPU0 via TTBR
> 0x000000004352d000
> (XEN) [ 12.338550] 0TH[0x014] = 0x4352cf7f
> (XEN) [ 12.341823] 1ST[0x000] = 0x4352bf7f
> (XEN) [ 12.345124] 2ND[0x001] = 0x40000043527f7f
> (XEN) [ 12.347329] 3RD[0x1ce] = 0x400000433cef7f
> (XEN) [ 12.351233] CPU0: Unexpected Trap: Instruction Abort
> (XEN) [ 12.357643] ----[ Xen-4.21.1 arm64 debug=n gcov=y Not tainted
> ]----
> (XEN) [ 12.360243] CPU: 0
> (XEN) [ 12.364098] PC: 00000a00003ce000 00000a00003ce000
> (XEN) [ 12.375835] LR: 00000a00004802f8
> (XEN) [ 12.378273] SP: 00000a00004c7e10
> (XEN) [ 12.380492] CPSR: 0000000080000249 MODE:64-bit EL2h
> (Hypervisor, handler)
> (XEN) [ 12.382785] X0: 00000a00003ce000 X1: 0000000000000000 X2:
> 00000a0000410fa0
> (XEN) [ 12.385176] X3: 0000000000000000 X4: 0000000000000010 X5:
> 0000000000000001
> (XEN) [ 12.387555] X6: 00000a00004e5f40 X7: 00000a00004e5f38 X8:
> 0000000000000000
> (XEN) [ 12.390027] X9: 00000a00004e5f20 X10: 00000a00004e5f30 X11:
> 00000a00004e5f40
> (XEN) [ 12.392510] X12: 00000a0000439748 X13: 00000a0000406938 X14:
> 000000000000062e
> (XEN) [ 12.394954] X15: 00000a00004f3918 X16: 00000a00004c7bb5 X17:
> 00000000004c7bb5
> (XEN) [ 12.397293] X18: 0000000000000030 X19: 000000000000001d X20:
> 00000000000000a9
> (XEN) [ 12.399803] X21: 00000a00004c8008 X22: 00000a00003fa000 X23:
> 00000a00004e2000
> (XEN) [ 12.402392] X24: 00000a00003f9390 X25: 00000a00003fa000 X26:
> 00000a00003f4ca8
> (XEN) [ 12.404798] X27: 0000000000000002 X28: 00000a000057a9c0 FP:
> 00000000bedb6740
> (XEN) [ 12.407110]
> (XEN) [ 12.409442] VTCR_EL2: 0000000080023558
> (XEN) [ 12.411291] VTTBR_EL2: 00000000bffc4000
> (XEN) [ 12.412895]
> (XEN) [ 12.414204] SCTLR_EL2: 0000000030cd183d
> (XEN) [ 12.415928] HCR_EL2: 0000000000000039
> (XEN) [ 12.417642] TTBR0_EL2: 000000004352d000
> (XEN) [ 12.419152]
> (XEN) [ 12.420327] ESR_EL2: 000000008600000f
> (XEN) [ 12.422056] HPFAR_EL2: 0000000000000000
> (XEN) [ 12.423809] FAR_EL2: 00000a00003ce000
> ...
> (XEN) [ 12.485355] Xen call trace:
> (XEN) [ 12.489080] [<00000a00003ce000>] 00000a00003ce000 (PC)
> (XEN) [ 12.512076] [<00000a00004802f8>] init_constructors+0x38/0x50
> (LR)
>
> Observed failing symbol:
> _sub_I_00100_0
> called from:
> init_constructors()
> The issue can be diagnosed by enabling linker orphan diagnostics or
> generating a linker map:
> LDFLAGS += "--orphan-handling=warn"
> LDFLAGS += "-Map=xen.map"
> and then inspecting orphaned executable sections such as:
> .text.startup
>
> Place .text.startup in .init.text on the non-x86 linker scripts,
> matching the existing x86 behavior.
>
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
> ---
> Changes in v2:
> - do not add *(.text.*) when CONFIG_COVERAGE is enables
> - copy the existing x86 linker script behavior to the non-x86 linker scripts
> (put .text.startup into .init.text on Arm, RISC-V and PPC)
> - update commit subject and message accordingly
>
> Link to v1:
> https://patchew.org/Xen/cb8c1e0862a554f7a28347f549e9cfd0b0d6db2f.1779829545.git.dmytro._5Fprokopchuk1@xxxxxxxx/
What about my feedback to v1 which showed that .text.startup
specifically is buggy in x86, and provided a suggestion of what to do
about it?
~Andrew
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