From f802ff1e281eac50f2b4b177b180be97e80da21f Mon Sep 17 00:00:00 2001 From: Daniel Bertalan Date: Tue, 25 Apr 2023 10:34:31 +0000 Subject: [PATCH] hw/arm/bcm2835_property: Implement "get command line" message This query copies the kernel command line into the message buffer. It was previously stubbed out to return empty, this commit makes it reflect the arguments specified with `-append`. I observed the following peculiarities on my Pi 3B+: - If the buffer is shorter than the string, the response header gives the full length, but no data is actually copied. - No NUL terminator is added: even if the buffer is long enough to fit one, the buffer's original contents are preserved past the string's end. - The VC firmware adds the following extra parameters beside the user-supplied ones (via /boot/cmdline.txt): `video`, `vc_mem.mem_base` and `vc_mem.mem_size`. This is currently not implemented in qemu. Signed-off-by: Daniel Bertalan Message-id: 20230425103250.56653-1-dani@danielbertalan.dev Reviewed-by: Peter Maydell [PMM: added comment about NUL and short-buffer behaviour] Signed-off-by: Peter Maydell --- hw/arm/bcm2835_peripherals.c | 2 ++ hw/arm/bcm2836.c | 2 ++ hw/arm/raspi.c | 2 ++ hw/misc/bcm2835_property.c | 13 ++++++++++++- include/hw/misc/bcm2835_property.h | 1 + 5 files changed, 19 insertions(+), 1 deletion(-) diff --git a/hw/arm/bcm2835_peripherals.c b/hw/arm/bcm2835_peripherals.c index 3c2a4160cd..0233038b95 100644 --- a/hw/arm/bcm2835_peripherals.c +++ b/hw/arm/bcm2835_peripherals.c @@ -90,6 +90,8 @@ static void bcm2835_peripherals_init(Object *obj) TYPE_BCM2835_PROPERTY); object_property_add_alias(obj, "board-rev", OBJECT(&s->property), "board-rev"); + object_property_add_alias(obj, "command-line", OBJECT(&s->property), + "command-line"); object_property_add_const_link(OBJECT(&s->property), "fb", OBJECT(&s->fb)); diff --git a/hw/arm/bcm2836.c b/hw/arm/bcm2836.c index f894338fc6..166dc896c0 100644 --- a/hw/arm/bcm2836.c +++ b/hw/arm/bcm2836.c @@ -55,6 +55,8 @@ static void bcm2836_init(Object *obj) TYPE_BCM2835_PERIPHERALS); object_property_add_alias(obj, "board-rev", OBJECT(&s->peripherals), "board-rev"); + object_property_add_alias(obj, "command-line", OBJECT(&s->peripherals), + "command-line"); object_property_add_alias(obj, "vcram-size", OBJECT(&s->peripherals), "vcram-size"); } diff --git a/hw/arm/raspi.c b/hw/arm/raspi.c index 92d068d1f9..7b9221c924 100644 --- a/hw/arm/raspi.c +++ b/hw/arm/raspi.c @@ -280,6 +280,8 @@ static void raspi_machine_init(MachineState *machine) object_property_add_const_link(OBJECT(&s->soc), "ram", OBJECT(machine->ram)); object_property_set_int(OBJECT(&s->soc), "board-rev", board_rev, &error_abort); + object_property_set_str(OBJECT(&s->soc), "command-line", + machine->kernel_cmdline, &error_abort); qdev_realize(DEVICE(&s->soc), NULL, &error_fatal); /* Create and plug in the SD cards */ diff --git a/hw/misc/bcm2835_property.c b/hw/misc/bcm2835_property.c index de056ea2df..251b3d865d 100644 --- a/hw/misc/bcm2835_property.c +++ b/hw/misc/bcm2835_property.c @@ -282,7 +282,17 @@ static void bcm2835_property_mbox_push(BCM2835PropertyState *s, uint32_t value) break; case 0x00050001: /* Get command line */ - resplen = 0; + /* + * We follow the firmware behaviour: no NUL terminator is + * written to the buffer, and if the buffer is too short + * we report the required length in the response header + * and copy nothing to the buffer. + */ + resplen = strlen(s->command_line); + if (bufsize >= resplen) + address_space_write(&s->dma_as, value + 12, + MEMTXATTRS_UNSPECIFIED, s->command_line, + resplen); break; default: @@ -420,6 +430,7 @@ static void bcm2835_property_realize(DeviceState *dev, Error **errp) static Property bcm2835_property_props[] = { DEFINE_PROP_UINT32("board-rev", BCM2835PropertyState, board_rev, 0), + DEFINE_PROP_STRING("command-line", BCM2835PropertyState, command_line), DEFINE_PROP_END_OF_LIST() }; diff --git a/include/hw/misc/bcm2835_property.h b/include/hw/misc/bcm2835_property.h index 712b76b7a3..ba8896610c 100644 --- a/include/hw/misc/bcm2835_property.h +++ b/include/hw/misc/bcm2835_property.h @@ -30,6 +30,7 @@ struct BCM2835PropertyState { MACAddr macaddr; uint32_t board_rev; uint32_t addr; + char *command_line; bool pending; };