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Re: [PATCH v2 1/4] target/ppc: initialize 'val' union in kvm_get_one_spr
From: |
David Gibson |
Subject: |
Re: [PATCH v2 1/4] target/ppc: initialize 'val' union in kvm_get_one_spr() |
Date: |
Thu, 31 Mar 2022 12:20:22 +1100 |
On Wed, Mar 30, 2022 at 09:17:14PM -0300, Daniel Henrique Barboza wrote:
> Valgrind isn't convinced that we are initializing the values we assign
> to env->spr[spr] because it doesn't understand that the 'val' union is
> being written by the kvm_vcpu_ioctl() that follows (via struct
> kvm_one_reg).
>
> This results in Valgrind complaining about uninitialized values every
> time we use env->spr in a conditional, like this instance:
>
> ==707578== Thread 1:
> ==707578== Conditional jump or move depends on uninitialised value(s)
> ==707578== at 0xA10A40: hreg_compute_hflags_value (helper_regs.c:106)
> ==707578== by 0xA10C9F: hreg_compute_hflags (helper_regs.c:173)
> ==707578== by 0xA110F7: hreg_store_msr (helper_regs.c:262)
> ==707578== by 0xA051A3: ppc_cpu_reset (cpu_init.c:7168)
> ==707578== by 0xD4730F: device_transitional_reset (qdev.c:799)
> ==707578== by 0xD4A11B: resettable_phase_hold (resettable.c:182)
> ==707578== by 0xD49A77: resettable_assert_reset (resettable.c:60)
> ==707578== by 0xD4994B: resettable_reset (resettable.c:45)
> ==707578== by 0xD458BB: device_cold_reset (qdev.c:296)
> ==707578== by 0x48FBC7: cpu_reset (cpu-common.c:114)
> ==707578== by 0x97B5EB: spapr_reset_vcpu (spapr_cpu_core.c:38)
> ==707578== by 0x97BABB: spapr_cpu_core_reset (spapr_cpu_core.c:209)
> ==707578== Uninitialised value was created by a stack allocation
> ==707578== at 0xB11F08: kvm_get_one_spr (kvm.c:543)
>
> Initializing 'val' has no impact in the logic and makes Valgrind output
> more bearable.
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> ---
> target/ppc/kvm.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index dc93b99189..858866ecd4 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -543,10 +543,11 @@ static void kvm_get_one_spr(CPUState *cs, uint64_t id,
> int spr)
> {
> PowerPCCPU *cpu = POWERPC_CPU(cs);
> CPUPPCState *env = &cpu->env;
> + /* Init 'val' to avoid "uninitialised value" Valgrind warnings */
> union {
> uint32_t u32;
> uint64_t u64;
> - } val;
> + } val = { };
> struct kvm_one_reg reg = {
> .id = id,
> .addr = (uintptr_t) &val,
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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[PATCH v2 4/4] target/ppc: init 'rmmu_info' in kvm_get_radix_page_info(), Daniel Henrique Barboza, 2022/03/30
[PATCH v2 3/4] target/ppc: init 'sregs' in kvmppc_put_books_sregs(), Daniel Henrique Barboza, 2022/03/30