[PATCH] powerpc/64e: Fix secondary thread bringup for ELFv2 kernels

Michael Ellerman mpe at ellerman.id.au
Tue Aug 1 20:26:50 AEST 2023

When booting on e6500 with an ELF v2 ABI kernel, the secondary threads do
not start correctly:

    [    0.051118] smp: Bringing up secondary CPUs ...
    [    5.072700] Processor 1 is stuck.

This occurs because the startup code is written to use function
descriptors when loading the entry point for the secondary threads. When
building with ELF v2 ABI there are no function descriptors, and the code
loads junk values for the entry point address.

Fix it by using ppc_function_entry() in C, and DOTSYM() in asm, both of
which work correctly for ELF v2 ABI as well as ELF v1 ABI kernels.

Fixes: 8c5fa3b5c4df ("powerpc/64: Make ELFv2 the default for big-endian builds")
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
 arch/powerpc/kernel/head_64.S     | 3 +--
 arch/powerpc/platforms/85xx/smp.c | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index f132d8704263..6440b1bb332a 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -375,8 +375,7 @@ _GLOBAL(generic_secondary_smp_init)
 	beq	20f
 	/* start the specified thread */
-	LOAD_REG_ADDR(r5, fsl_secondary_thread_init)
-	ld	r4, 0(r5)
+	LOAD_REG_ADDR(r5, DOTSYM(fsl_secondary_thread_init))
 	bl	book3e_start_thread
 	/* stop the current thread */
diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index 9c43cf32f4c9..40aa58206888 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c
@@ -180,7 +180,7 @@ static void wake_hw_thread(void *info)
 	unsigned long inia;
 	int cpu = *(const int *)info;
-	inia = *(unsigned long *)fsl_secondary_thread_init;
+	inia = ppc_function_entry(fsl_secondary_thread_init);
 	book3e_start_thread(cpu_thread_in_core(cpu), inia);

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